- Zurich, Switzerland
Mohsén Bazärgan
Uppsala University, Department of Earth Sciences, Graduate Student
- I have a doctorate in computational Volcano-tectonics from RHUL. My second doctorate is in experimental and computati... moreI have a doctorate in computational Volcano-tectonics from RHUL. My second doctorate is in experimental and computational rock physics and rock mechanics from UU. Post Doctorate in geotechnical engineering. Rock and Geological Engineering section of Rejlers.edit
- Agust gudmundsson, Bjarne G Almqvist, Christoph F Heironymus, Flavio Lanaro, Sandra Piazolo, Marcia Phillips, Philip G Meredithedit
Geothermal exploration targets large magmatic intrusions as heat sources because of their size, longevity, and amount of stored energy, but as shallow volcanic plumbing systems comprise numerous smaller intrusions, their geothermal... more
Geothermal exploration targets large magmatic intrusions as heat sources because of their size, longevity, and amount of stored energy, but as shallow volcanic plumbing systems comprise numerous smaller intrusions, their geothermal potential warrants consideration. Here, we evaluate the geothermal impact of dykes and sills on caldera-infill rocks. We present geological data and geothermometry on intrusions in the eroded Breiðuvík caldera in Northeast Iceland, which serves as an analogue to the active, and geothermally exploited, Krafla volcano. These data inform 2D finite element models of dyke and sill intrusions that consider heat transfer in porous media. Our results indicate that small intrusions create considerable thermal anomalies in their immediate vicinity. These anomalies are larger-magnitude and longer-lasting for individual thick sills and dykes, but networks of smaller sills and dykes emplaced close in time and space can create more widespread thermal anomalies that may be viable economic targets for decades after their emplacement. ÁGRIP Jarðhitarannsóknir miða oftast að því að finna stór kvikuinnskot sem hitagjafa í jarðhitakerfum vegna lengd storknunartíma og magni af orku. Grynnri hluti kvikuflutningskerfa eldfjalla samanstendur af fjölda minni kvikuinnskota sem gefur tilefni til frekari rannsókna á þeim sem hitagjafa. Þessi rannsókn metur áhrif lóðréttra (gangar) og láréttra (sillur) kvikuinnskota á jarðhitakerfi í öskjum. Jarðfraeði og efnasamsetning kvikuinnskota í Breiðuvíkur eldstöðinni, sem er rofin megineldstöð staðsett á norðausturhluta Íslands, er kynnt og notuð sem hliðstaeða við jarðhitakerfið í Kröflu sem í dag er nýtt til orkuframleiðslu. Gögnin eru notuð í tvívíð reiknilíkön af kvikuinnskotum sem áaetla varmaflutning í gropnu bergi. Niðurstöður rannsóknarinnar benda til þess að minni innskot valdi umtalsverðu hitafráviki í sínu naesta umhverfi. Slík frávik eru haerri og langlífari fyrir einstaka þykkari innskot. Kerfi af fjölda minni innskota mynduð naerri í tíma og rúmi geta framkallað umfangsmeiri hitafrávik sem gaetu verið raunhaef til jarðhitavinnslu áratugum eftir myndun innskotana.
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This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
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As a petrofabric indicator, anisotropy of magnetic susceptibility (AMS) can potentially be used to infer seismic properties of rocks, and in particular seismic anisotropy. To evaluate the link between AMS and seismic anisotropy we present... more
As a petrofabric indicator, anisotropy of magnetic susceptibility (AMS) can potentially be used to infer seismic properties of rocks, and in particular seismic anisotropy. To evaluate the link between AMS and seismic anisotropy we present laboratory measurements of elastic wave velocities and anisotropy of magnetic susceptibility (AMS) for eight samples from the deep drilling investigation forming a part of the Collisional Orogeny in the Scandinavian Caledonides (COSC) project. The samples consist of a representative suite of mid crustal, deformed rock types, namely felsic and biotite-rich gneisses, and amphibolites (mafic gneisses). Compressional (P) and shear (S) waves were measured at confining pressures from ambient to 600 MPa and temperature from room condition to 600 °C. Seismic anisotropy changes with increasing temperature and pressure, where the effect of pressure is more significant than temperature. Increasing pressure results in an increase in mean wave speed values from 4.52 to 7.86 km/s for P waves and from 2.75 to 4.09 km/s for S waves. Biotite gneiss and amphibolite exhibit the highest anisotropy with P wave velocity anisotropy (AVp) in the ranges of ~9% to ~20%, and maximum S- wave anisotropy exceeds 10 %. In contrast, Felsic gneisses are significantly less anisotropic, with AVp of <7 % and AVs of <6 %. Up to 20 % anisotropy may be generated by microcracks at 600 MPa and 600 °C, which is likely originating from thermal expansion of anisotropic minerals. An agreement is found between AMS and seismic anisotropy, although this is only a case if mean magnetic susceptibility (kmean) ranges between ~1×10-5 to ~1×10-3 [SI]. Such kmean values are common in rocks dominated by paramagnetic matrix minerals. Based on our results we propose that such samples are the most likely to be useful for the prediction of seismic anisotropy based on their AMS data.
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Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (for example, magma... more
Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (for example, magma recharge rates) remain poorly understood. Here we compare an approximately 360-kyr-long record of effusive and explosive eruptions from the flooded caldera volcano at Santorini (Greece) with a high-resolution sea-level record spanning the last four glacial-interglacial cycles. Numerical modelling shows that when the sea level falls by 40 m below the present-day level, the induced tensile stresses in the roof of the magma chamber of Santorini trigger dyke injections. As the sea level continues to fall to −70 or −80 m, the induced tensile stress spreads throughout the roof so that some dykes reach the surface to feed eruptions. Similarly, the volcanic activity gradually disappears after the sea level rises above −40 m. Synchronizing Santorini’s stratigraphy with the sea-level record using tephra layers in marine sediment cores shows that 208 out of 211 eruptions (both effusive and explosive) occurred during periods constrained by sea-level falls (below −40 m) and subsequent rises, suggesting a strong absolute sea-level control on the timing of eruptions on Santorini—a result that probably applies to many other volcanic islands around the world.
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Managed Pressure Drilling (MPD) is a form of drilling which allows greater and more precise wellbore pressure control than conventional drilling also, the mud weight used will be lower than for the conventional mud weight and a secondary... more
Managed Pressure Drilling (MPD) is a form of drilling which allows greater and more precise wellbore pressure control than conventional drilling also, the mud weight used will be lower than for the conventional mud weight and a secondary choke or frictional pressure will be applied on the surface to create a combined annular pressure profile within the well. In this paper, it was attempted to investigate the effect of high power fiber laser heat tension to carbonate rock body of Kangan formation (K2) during irradiation process with an accurate simulation work and compare the model with experimental results. In commence the enforced stress by heat from the laser source and was analyzed and the fracture propagation pattern in rock body entire irradiation was obtained. This research presented the weakening and fracturing mechanism which generated from heat exposer during laser irradiation and achieved to numerical results for fracture pressure before and after laser irradiation. Also, the MPD as an effective technology to control of this induced anomaly was proposed during Laser-Assisted Drilling (LAD) operation to prevent any loss, gain or hole instability or other drilling problem related to this fracturing and weakening.
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The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project focuses on mountain building processes in a major mid-Paleozoic orogen in western Scandinavia and its comparison with modern analogues. The... more
The Collisional Orogeny in the Scandinavian Caledonides (COSC) scientific drilling project focuses on mountain building processes in a major mid-Paleozoic orogen in western Scandinavia and its comparison with modern analogues. The transport and emplacement of subduction-related highgrade continent-ocean transition (COT) complexes onto the Baltoscandian platform and their influence on the underlying allochthons and basement is being studied in a section provided by two fully cored 2.5 km deep drill holes. These operational data sets concern the second drill site, COSC-2 (boreholes ICDP 5054-2-A and 5054-2-B), drilled from mid April to early August 2020. COSC-2 is located approximately 20 km eastsoutheast of COSC-1, close to the southern shore of Lake Liten between Järpen and Mörsil in Jämtland, Sweden. COSC-2 drilling started at a tectonostratigraphic level slightly below that at COSC-1’s total depth. It has sampled the Lower Allochthon, the main Caledonian décollement and the underlying basement of the Fennoscandian Shield, including its Neoproterozoic and possibly older sedimentary cover. COSC-2 A reached 2276 m driller's depth with nearly 100 % core recovery between 100 m and total depth. COSC-2 B, with a driller’s depth of 116 m, covers the uppermost part of the section that was not cored in COSC-2 A. The operational data sets include the drill core documentation from the drilling information system (mDIS), full round core scans, MSCL data sets, a preliminary core description and the geophysical downhole logging data that were acquired during and subsequent to the drilling operations. All downhole logs and core depth were subject to depth correction to a common depth master (cf. operational report for detailed information). The COSC-2 drill core is archived at the Core Repository for Scientific Drilling at the Federal Institute for Geosciences and Natural Resources (BGR), Wilhelmstr. 25–30, 13593 Berlin (Spandau), Germany.
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Elongate inclusions immersed in a viscous fluid generally rotate at a rate that is different from the local angular velocity of the flow. Often, a net alignment of the inclusions develops, and the resulting shape preferred orientation of... more
Elongate inclusions immersed in a viscous fluid generally rotate at a rate that is different from the local angular velocity of the flow. Often, a net alignment of the inclusions develops, and the resulting shape preferred orientation of the particle ensemble can then be used as a strain marker that allows reconstruction of the fluid's velocity field. Much of the previous work on the dynamics of flow-induced particle rotations has focused on spatially homogeneous flows with large-scale tectonic deformations as the main application. Recently, the theory has been extended to spatially varying flows, such as magma with embedded crystals moving through a volcanic plumbing system. Additionally, an evolution equation has been introduced for the probability density function of crystal orientations. Here, we apply this new theory to a number of simple, 2-D flow geometries commonly encountered in magmatic intrusions, such as flow from a dyke into a reservoir or from a reservoir into a dyke, flow inside an inflating or deflating reservoir, flow in a dyke with a sharp bend, and thermal convection in a magma chamber. The main purpose is to provide a guide for interpreting field observations and for setting up more complex flow models with embedded crystals. As a general rule, we find that a larger aspect ratio of the embedded crystals causes a more coherent alignment of the crystals, while it has only a minor effect on the geometry of the alignment pattern. Due to various perturbations in the crystal rotation equations that are expected in natural systems, we show that the time-periodic behaviour found in idealized systems is probably short-lived in nature, and the crystal alignment is well described by the time-averaged solution. We also confirm some earlier findings. For example, near channel walls, fluid flow often follows the bounding surface and the resulting simple shear flow causes preferred crystal orientations that are approximately parallel to the boundary. Where pure shear deformation dominates, there is a tendency for crystals to orient themselves in the direction of the greatest tensile strain rate. Where flow impinges on a boundary, for example in an inflating magma chamber or as part of a thermal convection pattern, the stretching component of pure shear aligns with the boundary, and the crystals orient themselves in that direction. In the field, this local pattern may be difficult to distinguish from a boundary-parallel simple shear flow. Pure shear also dominates along the walls of a deflating magma chamber and in places where the flow turns away from the reservoir walls, but in these locations, the preferred crystal orientation is perpendicular to the wall. Overall, we find that our calculated patterns of crystal orientations agree well with results from analogue experiments where similar geometries are available.
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Currently, the sheet-intrusion paths and geometries, including the sheet opening/thickness as well as the depth to sheet tip, are commonly determined from geodetic surface data using elastic dislocation models. These models assume the... more
Currently, the sheet-intrusion paths and geometries, including the sheet opening/thickness as well as the depth to sheet tip, are commonly determined from geodetic surface data using elastic dislocation models. These models assume the volcanic zone/volcano to be an elastic half space of uniform mechanical properties. Field observations, however, show that volcanic zones/volcanoes are composed of numerous layers whose mechanical properties (primarily Young’s modulus) vary widely. Here we provide new numerical models on the effects of a typical variation in Young’s modulus in an active volcanic zone/central volcano on the internal and surface stresses and displacements induced by a sheet-intrusion whose tip is arrested at a depth below the surface of 100 m. The sheet has a dip dimension (height) of 2 km. Its opening (thickness) depends on the magmatic overpressure, sheet dimension and host-rock Young’s modulus. For the values used here, sheet thickness would be in the range of 0.5-1.4 m, similar to commonly measured sheet thicknesses in the field. The only loading is internal magmatic overpressure in the sheet of 5 MPa. The modelled crustal segment/volcano consists of 5 layers, all with the same Poisson’s ratio (0.25). Each of the 4 uppermost layers is 10 m thick. Layer 1 (the top or surface layer) has a Young’s modulus of 3 GPa, layer 2 a modulus of 20 GPa, layer 3 a modulus of 30 GPa, and layer or unit 5 a modulus of 40 GPa. We vary the Young’s modulus or stiffness of the fourth layer from 10 GPa to 0.01 GPa, while the dip of the sheet takes the following values: 30°, 45°, 60° (for an inclined sheet) and 90° (for a dike). The resulting displacement and stresses are highly asymmetric across the sheet tip (except for the dike), with the main surface stresses and displacements being above the dipping sheet and highest for the 30°-dipping sheet. For comparison, three elastic half-space models of the same sheet configuration and loading but uniform Young’s modulus in each model (40GPa, 20GPa, and 10 GPa), all yield much higher surface stresses and displacements than any of the layered models. As the stiffness of layer 4 decreases the surface stresses gradually decrease while changes in vertical displacements are comparatively small but greater in horizontal displacements. In particular, as the stiffness of layer 4 decreases from 10 GPa to 0.01 GPa, for the 30°-dipping sheet the maximum surface shear stress decreases from about 6.6 MPa to 2.2 MPa and the maximum tensile stress from about 6.9 MPa to about 2.3 MPa. Thus, even a single comparatively thin (10 m) soft layer close to the surface of a central volcano/volcanic zone (where such layers are almost universal), may cause a great change in the maximum sheet-induced stresses at the surface and, thereby, in any sheet-induced fracture pattern. Furthermore, the stress peaks do not coincide with the displacement peaks; fracture formation is most likely at the location of the stress peaks. The results have important implications for the correct interpretation of geodetic data and fracturing during unrest periods with magma-chamber rupture and sheet injection.
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Magmas and other viscously deforming fluids in Earth sciences frequently contain embedded crystals or other solid inclusions. These inclusions generally rotate about their own axis and, under certain conditions, align themselves in a... more
Magmas and other viscously deforming fluids in Earth sciences frequently contain embedded crystals or other solid inclusions. These inclusions generally rotate about their own axis and, under certain conditions, align themselves in a direction dictated by the details of the flow. While this rotational behavior has been studied extensively for homogeneous flows, we couple the crystal rotation dynamics with the Navier-Stokes equation of fluid mechanics, thus allowing the analysis of crystal rotations in flows that are variable in both space and time. The solution is valid provided that the inter-crystal spacing is sufficiently large to preclude interaction between crystals. Additionally, we derive an evolution equation for the probability density function of crystal orientations based on the general concept of conservation in continuum mechanics. The resulting system is extensively tested against previous analytical and numerical solutions. Given the focus on method validation, we limit the fluid mechanics to simple systems with analytical solutions for the velocity field. Future application to more complex flow fields is expected to improve our ability to interpret field observations of crystal alignment in solidified magma flows.
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Nakhlite meteorites are ~1.4 to 1.3 Ga old igneous rocks, aqueously altered on Mars ~630 Ma ago. We test the theory that water-rock interaction was impact driven. Electron backscatter diffraction demonstrates that the meteorites Miller... more
Nakhlite meteorites are ~1.4 to 1.3 Ga old igneous rocks, aqueously altered on Mars ~630 Ma ago. We test the theory that water-rock interaction was impact driven. Electron backscatter diffraction demonstrates that the meteorites Miller Range 03346 and Lafayette were heterogeneously deformed, leading to localized regions of brecciation, plastic deformation, and mechanical twinning of augite. Numerical modeling shows that the pattern of deformation is consistent with shock-generated compressive and tensile stresses. Mesostasis within shocked areas was aqueously altered to phyllosilicates, carbonates, and oxides, suggesting a genetic link between the two processes. We propose that an impact ~630 Ma ago simultaneously deformed the nakhlite parent rocks and generated liquid water by melting of permafrost. Ensuing water-rock interaction focused on shocked mesostasis with a high density of reactive sites. The nakhlite source location must have two spatially correlated craters, one ~630 Ma old and another, ejecting the meteorites, ~11 Ma ago.
Research Interests: Mars and Martian Surface
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The Karlıova triple junction (KTJ) in eastern Turkey has been subjected to incremental deformation resulting in complex kinematic and mechanical interactions throughout the upper crust. These interactions have generated tectonic... more
The Karlıova triple junction (KTJ) in eastern Turkey has been subjected to incremental deformation resulting in complex kinematic and mechanical interactions throughout the upper crust. These interactions have generated tectonic inversions and uplift, extensive seismicity and volcanism. The regional tectonics generate local stresses, some of which are favorable to magma transport and thermal water circulation throughout the lithosphere. Here we evalauate hydrogeochemical, geological and numerical results relating to the mechanism of thermal fluid circulation around the KTJ. Hydrogeochemistry of the samples indicates that the thermal water springs are probably heated by steam. Volcanic rocks at the site appear to be the host rock owing to the enrichment of Na + and Cl − ions in water and the abundance of these elements in minerals of the volcanic rocks. In addition, it is clear that the thermal fluids are sourced from depth and migrate through permeable networks of faults. The effects of crustal heterogeneities, in particular the geometry and mechanical properties of many faults and layers, on thermal fluid circulation in relation to active magma chambers were investigated under a variety of different mechanical conditions. The numerical results indicate very close relationships between the stress field causing faulting and thermal fluid movement in the KTJ. The effect of thermal transfer was modeled with depth throughout the crust and along the the crustal surface. The models show that some faults encourage thermal fluid circulation below the Varto and Özenç volcanoes. Hydrogeochemical, geological and numerical results suggest that magmas residing beneath both the Varto caldera and the Özenç volcano are the main heat source for thermal fluid in the Varto region. Fluid-solid interactions and fluid circulation models show that the permeable faults are important factors affecting heat transport and fluid circulation. In a series of thermal fluid flow models we probe the mechanism for fluid and gas transport from the 900°C 'hot' zone around the deep magma chambers and investigate how heat is lost throughout the crust on the way to the surface and so eventually creates water channels of temperatures between 50 to 60°C.
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Few places on Earth are as tectonically active as the Karlıova region of eastern Turkey. In this region, complex interactions between the Arabian, Eurasian and Anatolian plates occur at the Karlıova Triple Junction (KTJ). The relationship... more
Few places on Earth are as tectonically active as the Karlıova region of eastern Turkey. In this region, complex interactions between the Arabian, Eurasian and Anatolian plates occur at the Karlıova Triple Junction (KTJ). The relationship between tectonics and magma propagation in triple-junction tectonic settings is poorly understood. Here we present new field and numerical results on the mechanism of magma propagation at the KTJ. We explore the effects of crustal heterogeneity and anisotropy, in particular the geometry and mechanical properties of many faults and layers, on magma propagation paths under a variety of tectonic loads. We propose that two major volcanic centres in the area, the Turnadağ volcano and the Varto caldera, are both fed by comparatively shallow magma chambers at depths of about 8 km, which, in turn, are fed by a single, much larger and deeper reservoir at about 15-18 km depth. By contrast, the nearby Özenç volcanic area is fed directly by the deeper reservoir. We present a series of two-dimensional and three-dimensional numerical models showing that the present tectonic stresses encourage magma-chamber rupture and dyke injection. The results show that inversion tectonics encourages the formation of magma paths as potential feeder dykes. Our three-dimensional models allow us to explore the local stresses induced by complex loading conditions at the Karlıova triple junction, using an approach that can in future be applied to other similar tectonic regions. The numerical results indicate a great complexity in the potential magma (dyke) paths, resulting from local stresses generated by interaction between mechanical layers, major faults, and magma chambers. In particular, the results suggest three main controls on magma path formation and, eventual eruptions, at KTJ: (1) the geometry and attitude of the associated faults; (2) the heterogeneity and anisotropic of the crust; and (3) mechanical (stress) interactions between deep and shallow magma chambers.
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In this paper, an enriched finite element technique is presented to simulate the mechanism of interaction between the hydraulic fracturing and frictional natural fault in impermeable media. The technique allows modeling the... more
In this paper, an enriched finite element technique is presented to simulate the mechanism of interaction between the hydraulic fracturing and frictional natural fault in impermeable media. The technique allows modeling the discontinuities independent of the finite element mesh by introducing additional degrees of freedom. The coupled equilibrium and flow continuity equations are solved using a staggered Newton solution strategy; and an algorithm is proposed on the basis of fixed-point iteration concept to impose the flow condition at the hydro-fracture mouth. The cohesive crack model is employed to introduce the nonlinear fracturing process occurring ahead of the hydro-fracture tip. Frictional contact is modeled along the natural fault using the penalty method within the framework of plasticity theory of friction. Moreover, an experimental investigation is carried out to perform the hydraulic fracturing experimental test in fractured media under plane strain condition. The results of several numerical and experimental simulations are presented to verify the accuracy and robustness of proposed computational algorithm as well as to investigate the mechanisms of interaction between the hydraulically-driven fracture and frictional natural fault.
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Laser rock spallation is a rock removal process that utilizes laser induced thermal stress to fracture and cause a break through the rock by creating small fragments before melting of the rock. In this paper we investigated the effects of... more
Laser rock spallation is a rock removal process that utilizes laser induced thermal stress to fracture and cause a break through the rock by creating small fragments before melting of the rock. In this paper we investigated the effects of CO 2 laser irradiation on limestone of Iran Sarvak formation. Since the limestone included heavy and light oil, we studied the amount of laser beam absorption by this oils for determining thermal fractured during the laser drilling laboratory process. In order to characterize this limestone spectrophotometry (from UV to NIR), scanning electron microscopy (SEM) have been used.
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Although many deep-seated magma reservoirs have been detected beneath active volcanic systems in Iceland in recent decades, none were detected beneath the 5 volcanic systems on the Reykjanes Peninsula (RP) before the year 2020. This area,... more
Although many deep-seated magma reservoirs have been detected beneath active volcanic systems in Iceland in recent decades, none were detected beneath the 5 volcanic systems on the Reykjanes Peninsula (RP) before the year 2020. This area, close to Iceland’s capital Reykjavik, was subject to an unrest period with numerous earthquakes, beginning in December 2019. Using this abundant seismicity to produce tomographic images of the RP, we discovered a high Vp/Vs anomaly below the volcanic system of Fagradalsfjall – the smallest of the 5 systems on the RP. This anomaly is clear on images as early as May 2020 and we interpret it as the top part of the source reservoir of the Fagradalsfjall Volcanic System, which now supplies magma to the eruption that started there on 19 March 2021. From the tomographic images, we infer that the roof of the reservoir is at ~10 km below the surface of the volcanic system, but the reservoir itself extends much deeper. We interpret the results as magma accumulation in the upper part of the reservoir at least by May 2020, and probably earlier, resulting in a slight magma-pressure increase and doming of the reservoir roof. The associated stress changes in the roof triggered several earthquake swarms throughout 2020 and into early 2021.
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Pressure and temperature change simultaneously in the Earth's crust from surface to depth. Joint pressure and temperature changes influence many different physical properties. There are many studies on samples at elevated pressure, where... more
Pressure and temperature change simultaneously in the Earth's crust from surface to depth. Joint pressure and temperature changes influence many different physical properties. There are many studies on samples at elevated pressure, where the influence of open cracks, fractures, voids and pores have been studied. Applying confining pressure has a direct influence on crack closure, and this influence on dynamic properties (density and elastic modulus, bulk, shear and young's) of rocks above 200 MPa is assumed linear with the linear increase in wave speed. This is because it is generally assumed that most cracks are closed above 200 MPa, which in nature would correspond to a depth of ~7-8 km. However, from the KTB deep drilling well in Germany, it is known that fluid-filled fractures and pores can remain open until 8 to 9 km depth. Applying temperature can affect the dynamic properties of rock by thermal expansion, possibly reopening cracks that were closed at pressures >200 MPa, and thermally expanding grains. This influence is also assumed to be linear at a temperature below partial melting, and in the absence of phase transitions. A similar effect has been observed by a number of research groups during laboratory experiments and calculating seismic velocity results under 600 MPa confining pressure and 600 o C temperature. In this work, an effort has been made to mathematically investigate the influence of temperature and pressure on the seismic properties (velocity of pressure and shear waves, density and Poisson's ratio) of crystalline rocks, measured during laboratory experiments. Elastic wave speeds, moduli and density are increasing as a function of pressure and decreasing as a function of temperature. However, these pressure and temperature-related changes are shown to be nonlinear from room conditions up to 600 o C and 600 MPa. In this presentation, we focus on non-linear changes mainly in the high-pressure portion of the velocity as a function of pressure (>200 MPa). When confining pressure is applied, measured P-and S-waves show an increase in velocity and decrease in anisotropy. However, the effect of temperature on measured P-and S-waves show a decrease in velocity and increases in anisotropy. These changes are not very different from linear, but it is not possible to fit velocity as a function of pressure or temperature with linear mathematical functions. The implications of non-linear relationships between pressure, temperature and elastic wave speeds are discussed in this presentation.
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The volcanic eruption that began on 19 March 2021 at Fagradalsfjall is the first one to occur on the Reykjanes Peninsular for nearly 800 years and in Fagradalsfjall for about 6000 years. The feeder-dike was injected from a magma reservoir... more
The volcanic eruption that began on 19 March 2021 at Fagradalsfjall is the first one to occur on the Reykjanes Peninsular for nearly 800 years and in Fagradalsfjall for about 6000 years. The feeder-dike was injected from a magma reservoir whose top is at about 10 km depth below the surface (but the reservoir itself reaches much greater depths). The dike formation involved at least two roof ruptures and resulting dike segments. The first occurred on 24 February and the second on 14 March 2021. The first rupture, marked by earthquakes of M23 close to the contact between the roof and the magma, occurred in the eastern half of the toppart of the reservoir. An injected dike segment propagated towards the surface but became arrested at the depths of 0.5-2 km. As its vertical propagation became arrested, while continuing to receive magma, the segment spread laterally, reaching an overall maximum dike strike-dimension (length) of about 10 km. The second rupture, also marked by earthquakes of M2-3, occurred about 1 km to the west of the first rupture. The injected dike segment following the second rupture eventually resulted in the dike propagating to the surface to feed the eruption which started on 19 March. We estimate the average vertical rate of the feeder-dike propagation at about 0.02 m s-1. This is an order of magnitude lower than common rates of lateral dike propagation in rift zones, yet similar to the average rate during the Bardarbunga (Iceland) 2014 dike propagation (around 0.04 m s-1). The initial volcanic fissure fed by the second dike segment had a length of less than 200 m and an opening of a fraction of a metre. Subsequently, several more ‘dike-fingers’ reached the surface and generated volcanic fissure segments. The total length of the discontinuous, segmented fissure is many hundred metres – but only one crater is presently active. Using the aspect ratio of the fissure and basic fracture mechanics, we estimate the magmatic overpressure (driving pressure) at the beginning of the eruption as about 3 MPa. The low driving pressure and small fissure opening displacement and length are in harmony with the very low volumetric flow (effusion) rate of about 10 m3 s-1.
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Seismic anisotropy is a key property to understand the structure of the crust and mantle. In this contribution, we investigate the influence of shape (morphological) preferred orientation (SPO), crystallographic preferred orientation... more
Seismic anisotropy is a key property to understand the structure of the crust and mantle. In this contribution, we investigate the influence of shape (morphological) preferred orientation (SPO), crystallographic preferred orientation (CPO) and the spatial distribution of grains on seismic anisotropy in rocks (Bazargan et al., 2018). A numerical toolset has been developed with COMSOL to investigate these effects numerically, which has been benchmarked analytically and against other numerical models. Numerical samples modelled in 2D and 3D can determine anisotropy, by measurements along different sample axes, using different geometrical setups and mineral compositions. This numerical tool can include a variety of mineral arrangements and propagate P and S waves from different directions to calculate anisotropy. Current numerical results confirm directly the relations between the structural framework of the rocks (foliation, lineation) and velocity anisotropy, shear wave splitting and shear wave polarisation. This has been proven numerically with the effects of layering, which represents foliation and lineation in 2D. One of the aims of this work is to apply the fundamental results and effects of effective medium to improve our finite element method (FEM) toolbox to provide a numerical modelling tool for seismic data that have been collected in the field. Since the numerical and laboratory measurements are worked on together to verify the numerical results, to compare the models and explain the laboratory measurements have been conducted. Here we also present laboratory measurements of directional dependence of elastic waves velocity and shear wave splitting to the internal rock structure. In the experimental part of this study, we illustrate the contribution of microstructural parameters (grain sizes, SPO and microcracks) to the elastic anisotropy of relatively similar quartzites and granites. An objective with the laboratory measurements is to investigate the effect of grain size and its possible influence on elastic wave speed and potential scattering effects due to wavelength effects. Granites are the one we use to investigate anisotropy related to SPO and CPO. Our experimental data consist of the measurements of elastic wave velocities (Vp, Vs 1 and Vs 2) at confining pressures up to 600 MPa (Bazargan et al., 2019). numerical modelling together with laboratory measurements are used to obtain a better understanding of the role of microstructures in elastic wave propagation and its anisotropy
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Sheet intrusions supply magma to almost all eruptions. Mechanically, the erupting sheets are primarily extension fractures and of two main geometric types: dikes and inclined (cone) sheets. Regional dikes are mostly subvertical, many... more
Sheet intrusions supply magma to almost all eruptions. Mechanically, the erupting sheets are primarily extension fractures and of two main geometric types: dikes and inclined (cone) sheets. Regional dikes are mostly subvertical, many metres, occasionally tens of metres, thick, with strike dimensions (strike length) from kilometres to tens of kilometres (or more). By contrast, inclined sheets dip on average 30-40 • , are mostly less than one metre thick, and with strike dimension of hundreds of metres or, at most, a few kilometres. The density/frequency is also generally much greater in sheet swarms than in regional dike swarms. Forecasting the geometry and likely propagation path (including a possible eruption) of a sheet intrusion during volcanic unrest is of fundamental importance. The inferred geometry of the sheet is also an indication of the volume of magma that leaves the chamber during the unrest period. Sheet paths and geometries (including depth and opening/aperture) are commonly determined from geodetic surface data, in particular InSAR and GPS data. Standard interpretation methods of the data use mostly dislocation models that assume the volcano and the hosting crustal segment to be an elastic half space of uniform mechanical properties. By contrast, field observations of volcanoes (active and extinct) show that they are composed of a variety of layers whose mechanical properties vary widely. In particular, Young's modulus of layers and contacts in a typical active volcanic zone may vary by 2-3 orders of a magnitude. Here we provide numerical results on a dike/inclined sheet arrested at 0.5 km depth below the surface of an active volcano/volcanic zone, with several layers of varying stiffness (Young's modulus) between the tip of the dike/inclined sheet and the surface. In particular we vary the stiffness of one layer from 10 GPa to 0.01 GPa. The results show as the layer becomes more compliant (0.1-0.01 GPa) stresses and displacements (lateral and vertical) at the surface become suppressed. The results also show that the surface stresses and displacements induced by inclined sheets depend much on their dip and are generally widely different from those induced by vertical dikes. Also, the width of any dike-induced graben or zone of tension fractures is, according to the present results, roughly twice the depth to the tip of the arrested dike. In particular, the numerical results show that the surface-uplift peaks occur at locations which differ widely from those of the tensile/shear stress peaks and do not, in contrast with common interpretations, coincide with the location of the boundary faults of a dike-induce graben.
Al Shehri, A., Gudmundsson, A., 2018. Modelling of surface stresses and fracturing during dyke emplace-ment: Application to the 2009 episode at Harrat Lunayyir, Saudi Arabia. J. Volcanol. Geotherm. Res., 356, 278-303.
Bazargan, M., Gudmundsson, A., 2018. Dike-induced stresses and displacements in layered volcanic zones. J. Volcanology Geotherm. Res. (in press).
Al Shehri, A., Gudmundsson, A., 2018. Modelling of surface stresses and fracturing during dyke emplace-ment: Application to the 2009 episode at Harrat Lunayyir, Saudi Arabia. J. Volcanol. Geotherm. Res., 356, 278-303.
Bazargan, M., Gudmundsson, A., 2018. Dike-induced stresses and displacements in layered volcanic zones. J. Volcanology Geotherm. Res. (in press).
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It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that... more
It is of great importance in many fields to be able to forecast the likely propagation paths of fluid-driven factures. These include mineral veins, human-made hydraulic fractures, and dikes/inclined sheets. The physical principles that control the propagation of all fluid-driven fractures are the same. Here the focus is on dikes and inclined sheets where the selected path determines whether, where, and when a particular dike/sheet reaches the surface to erupt. Here we provide analytical and numerical models on dike/sheet paths in crustal segments (including volcanoes) that include layers of various types (lava flows, pyroclastic flows, tuff layers, soil layers, etc) as well as mechanically weak contacts and faults. The modelling results are then compared with, and tested on, actual data of two types. (a) Seismic data on the paths of dikes/sheets as well as human-made hydraulic fractures, and (b) field data on the actual propagation paths of dikes/sheets in layered and faulted rocks The numerical results show that, particularly in stratovolcanoes, the paths are likely to be complex with common deflections along layer contacts, in agreement with field observations. Also, some dikes/sheets may use existing faults as parts of their paths, primarily steeply dipping and recently active normal faults. The propagation path is thus not entirely in pure mode I but rather partly in a mixed mode. The energy required to propagate the dike/sheet is mainly the surface energy needed to rupture the rock, to form two new surfaces and move them apart as the fracture propagates. The energy available to drive the fracture is the stored elastic energy in the hosting crustal segment. From its point of initiation in the magma-chamber roof, a dike/sheet can, theoretically, select any one of an infinite number of paths to follow to its point of arrest or eruption. It is shown that the eventual path selected is the one of least action, that is, the path along which the time integral of the difference between the kinetic and potential energies is an extremum (normally a minimum) relative to all other possible paths with the same endpoints. If the kinetic energy is omitted, and there are no constraints, then least action becomes the minimum potential energy, which was postulated as a basis for understanding dike propagation by Gudmundsson (1986). Here it is shown how this theoretical framework can help us make reliable forecasts of dike/sheet paths and associated volcanic eruptions. Gudmundsson, A., 1986. Formation of dykes, feeder-dykes, and the intrusion of dykes from
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ABSTRACT In recent years, growing interest in underbalanced drilling has resulted in the rapid development of its associated equipment technology, practices, and procedures. Underbalanced drilling is used to avoid lost circulation,... more
ABSTRACT In recent years, growing interest in underbalanced drilling has resulted in the rapid development of its associated equipment technology, practices, and procedures. Underbalanced drilling is used to avoid lost circulation, formation damage, Invasion of drilling fluid, which occurs in almost all the permeable formations during drilling and decreasing weight on bit. However, the risk of wellbore collapse due to lake of hydrostatic mud pressure is high. Therefore, using good geo-mechanical model may avoid wellbore instability problem. In order to evaluate the potential for wellbore instability, it is necessary to use elastoplastic model to compute the stresses and strains around the bore hole. Furthermore it should be mentioned that the laser drilling process extremely depends on rock&#39;s geo-mechanical properties. This paper describes a numerical investigation of wellbore instability in a fractured carbonate reservoir and verified with reservoir core samples. Some necessary conditions should be mentioned to gain the best method of comparison conventional UBD and laser UBD operations. It is vital to evaluate the sensitivity of the wellbore stability by focusing on the effect of a laser irradiation absorption. Finally, this paper fills the gap by paying attention to the sensitivity analysis and focuses on assessing the influence of various drilling methods, rock properties and optical fluid parameters.
Few places on Earth are as tectonically active as the Karlıova region of eastern Turkey. In this region, complex interactions between the Arabian, Eurasian and Anatolian plates occur at the Karlıova Triple Junction (KTJ). The relationship... more
Few places on Earth are as tectonically active as the Karlıova region of eastern Turkey. In this region, complex interactions between the Arabian, Eurasian and Anatolian plates occur at the Karlıova Triple Junction (KTJ). The relationship between tectonics and magma propagation in triple-junction tectonic settings is poorly understood. Here we present new field and numerical results on the mechanism of magma propagation at the KTJ. We explore the effects of crustal heterogeneity and anisotropy, in particular the geometry and mechanical properties of many faults and layers, on magma propagation paths under a variety of tectonic loadings. We propose that two major volcanic centres in the area, the Turnadag volcano and the Varto caldera, are both fed by comparatively shallow magma chambers at depths of about 8 km, which, in turn, are fed by a single, much larger and deeper reservoir at about 15-18 km depth. By contrast, the nearby Özenç volcanic area is fed directly by the deeper reservoir. We present a series of two-dimensional and three-dimensional numerical models showing that the present tectonic stresses encourage magma-chamber rupture and dyke injection. The results show that inversion tectonics encourages the formation of magma paths as potential feeder dykes. Our three-dimensional models allow us to explore the local stresses induced by complex loading conditions at the Karlıova triple junction, using an approach that can in future be applied to other similar tectonic regions. The numerical results indicate a great complexity in the potential magma (dyke) paths, resulting from local stresses generated by interaction between mechanical layers, major faults, and magma chambers. In particular, the results suggest three main controls on magma path formation and eventual eruptions at KTJ: (1) the geometry and attitude of the associated faults; (2) the heterogeneity and anisotropy of the crust; and (3) mechanical (stress) interactions between deep and shallow magma chambers.
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Magmas and other viscously deforming fluids in the Earth frequently contain embedded crystals or other solid inclusions. These inclusions generally rotate about their own axis and, under certain conditions, align themselves in a direction... more
Magmas and other viscously deforming fluids in the Earth frequently contain embedded crystals or other solid inclusions. These inclusions generally rotate about their own axis and, under certain conditions, align themselves in a direction dictated by the details of the flow. This rotational behaviour has been studied extensively for homogeneous flows. Here, we couple the crystal rotation dynamics with the fluid mechanical Navier–Stokes equations for the large-scale flow, thus allowing the analysis of crystal rotations in settings that are variable in both space and time. The solution is valid provided that the intercrystal spacing is sufficiently large to preclude interaction between crystals. Additionally, we derive an evolution equation for the probability density function (PDF) of crystal orientations based on the fundamental concept of conservation of generic properties in continuum mechanics. The resulting system of equations is extensively tested against previous analytical and numerical solutions. Given the focus on method validation, we limit the fluid mechanics to simple systems with analytical solutions for the velocity field. Even for the simple examples computed, all of which are characterized by the fluid flow that is constant in time, the crystal orientation patterns are spatially complex and change in time. Pressure-driven flow in a channel results in coherent bands of crystal orientations with band thickness decreasing towards the channel walls. In corner flow constrained by two mutually perpendicular walls, the pattern of crystal orientations does not exhibit any significant similarity with the flow field. Given that there is no local one-to-one correspondence between the flow and the PDF pattern, a combined and larger-scale solution of the two systems is generally required. The simple flow examples shown demonstrate the viability of this new approach. Application to more complex flow geometries which may commonly occur in nature is deferred to future studies.
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Nakhlite meteorites are ~1.4 to 1.3 Ga old igneous rocks, aqueously altered on Mars ~630 Ma ago. We test the theory that water-rock interaction was impact driven. Electron backscatter diffraction demonstrates that the meteorites Miller... more
Nakhlite meteorites are ~1.4 to 1.3 Ga old igneous rocks, aqueously altered on Mars ~630 Ma ago. We test the theory that water-rock interaction was impact driven. Electron backscatter diffraction demonstrates that the meteorites Miller Range 03346 and Lafayette were heterogeneously deformed, leading to localized regions of brecciation, plastic deformation, and mechanical twinning of augite. Numerical modeling shows that the pattern of deformation is consistent with shock-generated compressive and tensile stresses. Mesostasis within shocked areas was aqueously altered to phyllosilicates, carbonates, and oxides, suggesting a genetic link between the two processes. We propose that an impact ~630 Ma ago simultaneously deformed the nakhlite parent rocks and generated liquid water by melting of permafrost. Ensuing water-rock interaction focused on shocked mesostasis with a high density of reactive sites. The nakhlite source location must have two spatially correlated craters, one ~630 Ma ...
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Employing novel drilling, and tunneling methods are active area of study since 1930s. In the present report, an Experimental study of the thermal impact of laser and plasma torch on carbonated rocks as part of thermal assisted drilling... more
Employing novel drilling, and tunneling methods are active area of study since 1930s. In the present report, an Experimental study of the thermal impact of laser and plasma torch on carbonated rocks as part of thermal assisted drilling operation is presented. The experimental findings are then evaluated and verified by the Kirch's equations for stresses and strains around a cylindrical borehole. Since it is vital to carefully studying the wellbore stability in this type of drilling method, especially if it is associated with underbalanced drilling (UBD) and or Managed pressure drilling (MPD), further numerical investigations are carried out to highlight the necessary considerations in this regard.
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ABSTRACT Drilling and completion account for a significant portion of development of oil and gas fields. Since the introduction of rotary drilling, the method of drilling of deep petroleum wells has not drastically changed. With the... more
ABSTRACT Drilling and completion account for a significant portion of development of oil and gas fields. Since the introduction of rotary drilling, the method of drilling of deep petroleum wells has not drastically changed. With the advanced laser capabilities of the 21st century it seems necessary to fully inveitigate the possibility of Laser drilling or Laser-assisted drilling methods. This paper describes a set of experiments on different carbonate rock samples that were irradiated by different types of thermal setups, namely CO2 laser and Plasma torch. The results are then compared to a numerical model that was developed using a Mathematica code.
ABSTRACT Whole level of the erosion and the resistance of rocks which were composed closured have been studied, besides, the impact of temperature and laser irradiation for more investigation about this issue has been involved before all.... more
ABSTRACT Whole level of the erosion and the resistance of rocks which were composed closured have been studied, besides, the impact of temperature and laser irradiation for more investigation about this issue has been involved before all. This subject more reveals the matter which laser absorption on the laboratory scale using laser to what extent can cause the augment of the relative permeability and secondary porosity of reservoir rock, that of the vertical and horizontal useful connectivity and eventually that of the positive transferability. This research has been carried out in the form of case study on one of Iranian south west formations in north east of Behbahan city in Iran, either the rate or generation of forming the subtle and large fractures has been studied by considering and preparing this section from rocks of stratified sequence of the laboratory area before and after the laser irradiation operation and various analyzer by the means of Spectrophotometer and advanced electron microscope. It should be noted that during the erosion and ablation in the laser drilling operation in the experimental rocks of considered field, given the capability of the field, the formation and field lithology we observed the creation of fractures at the level of micro and nano simultaneously whose vacant spaces were positive, and reservoir and some others were neutral, this fractures can be created by the rate of crude oil absorption. The main purpose of this study is to advance the operations towards the higher technology in order to the better efficiency in the field of the well completion to be gained improving the rate of oil production by the introduction of this modern method of improving and fracturing reservoir which uses certain specialized parameters and indicators, and, finally, the certain method that might be a better way to use laser irradiation on our chosen formation of Iran.
Recent advances in high power plasma torch technology provide an apparatus to replace the conventional perforation methods in oil and gas wells. High power plasma torches are capable of cutting and removing rocks textures efficiently and... more
Recent advances in high power plasma torch technology provide an apparatus to replace the conventional perforation methods in oil and gas wells. High power plasma torches are capable of cutting and removing rocks textures efficiently and they might be considered as one of the appropriate substitutions for current shaped charge perforation methods. According to its advantages the conventional shaped charge methods that one the important one is increasing permeability considerably and no need to have costly re-perforation operations to decreasing new formation damage named by perforation skin. Plasma torch perforation is gone along with heat flux generation. As the temperature increases during plasma torch operation, thermal energy accumulates the matrix expansion. This expansion generate thermal stresses induce the rock texture. Furthermore, thermal stresses exceeds the rock strength, thermal fractures will form in texture that mainly depend on rock thermal properties, pore size dist...
This paper was prepared for presentation at the SPE Kuwait International Petroleum Conference and Exhibition held in Kuwait City, Kuwait, 10–12 December 2012. This paper was selected for presentation by an SPE program committee following... more
This paper was prepared for presentation at the SPE Kuwait International Petroleum Conference and Exhibition held in Kuwait City, Kuwait, 10–12 December 2012. This paper was selected for presentation by an SPE program committee following review of information contained in an abstract submitted by the author(s). Contents of the paper have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material does not necessarily reflect any position of the Society of Petroleum Engineers, its officers, or members. Electronic reproduction, distribution, or storage of any part of this paper without the written consent of the Society of Petroleum Engineers is prohibited. Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied. The abstract must contain conspicuous acknowledgment of SPE copyright. Abstract whole level of the erosion and the resistance of rocks which were compose...
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The objectives of this study are 1) to depict the prevalence of moderate depressive symptoms (MDS) in adolescents living in California, 2) to examine the role of acculturation in reported MDS, and 3) to identify any relationship between... more
The objectives of this study are 1) to depict the prevalence of moderate depressive symptoms (MDS) in adolescents living in California, 2) to examine the role of acculturation in reported MDS, and 3) to identify any relationship between acculturation, "needing emotional help," and "receiving psychological or emotional counseling," as reported by adolescents with MDS. We analyzed data from a cross-sectional population-based telephone survey for adolescents who completed the California Health Interview Survey (CHIS) in 2007, 2009, and 2011-2012. The primary predictor variable was level of acculturation. Outcome variables were 1) the presence of MDS, 2) whether participants needed help with emotional problems, and 3) whether they had received psychological or emotional counseling. Of the sample (n = 9816), 6.0% had MDS; 50% of these reported needing help for emotional problems, and 30% reported receiving psychological/emotional counseling. Multivariate analysis that...
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ABSTRACT Searching for a mechanism underlying autoimmunity in autism, we postulated that gliadin peptides, heat shock protein 60 (HSP-60), and streptokinase (SK) bind to different peptidases resulting in autoantibody production against... more
ABSTRACT Searching for a mechanism underlying autoimmunity in autism, we postulated that gliadin peptides, heat shock protein 60 (HSP-60), and streptokinase (SK) bind to different peptidases resulting in autoantibody production against these components. We assessed this hypothesis in patients with autism and in those with mixed connective tissue diseases. Associated with antigliadin and anti-HSP antibodies, children with autism and patients with autoimmune disease developed anti-dipeptidylpeptidase I (DPP I), anti-dipeptidylpeptidase IV (DPP IV [or CD26]) and anti-aminopeptidase N (CD13) autoantibodies. A significant percentage of autoimmune and autistic sera were associated with elevated immunoglobulin G (IgG), IgM, or IgA antibodies against three peptidases, gliadin, and HSP-60. These antibodies are specific, since immune absorption demonstrated that only specific antigens (e.g., DPP IV absorption of anti-DPP IV), significantly reduced IgG, IgM, and IgA antibody levels. For direct demonstration of SK, HSP-60, and gliadin peptide binding to DPP IV, microtiter wells coated with DPP IV were reacted with SK, HSP-60, and gliadin. They were then reacted with anti-DPP IV or anti-SK, anti-HSP, and antigliadin antibodies. Adding SK, HSP-60, and gliadin peptides to DPP IV resulted in 27 to 43% inhibition of the DPP IV-anti-DPP IV reaction, but DPP IV-positive peptides caused 18 to 20% enhancement of antigen-antibody reactions. We propose that (i) superantigens (e.g., SK and HSP-60) and dietary proteins (e.g., gliadin peptides) in individuals with predisposing HLA molecules bind to aminopeptidases and (ii) they induce autoantibodies to peptides and tissue antigens. Dysfunctional membrane peptidases and autoantibody production may result in neuroimmune dysregulation and autoimmunity.
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Background:Aim: To examine racial/ethnic variations in the effect of parents’ subjective neighborhood safety on children’s cognitive performance. Methods: This cross-sectional study included 10,027 children from the Adolescent Brain... more
Background:Aim: To examine racial/ethnic variations in the effect of parents’ subjective neighborhood safety on children’s cognitive performance. Methods: This cross-sectional study included 10,027 children from the Adolescent Brain Cognitive Development (ABCD) study. The exposure variable was parents’ subjective neighborhood safety. The outcomes were three domains of children’s cognitive performance: general cognitive performance, executive functioning, and learning/memory. We used mixed-effects regression models for data analysis. Results: Overall, parents’ subjective neighborhood safety was positively associated with children’s executive functioning, but not general cognitive performance or learning/memory. Higher parents’ subjective neighborhood safety had a more positive influence on the executive functioning of non-Hispanic White than Asian American children. Higher parents’ subjective neighborhood safety was associated with higher general cognitive performance and learning/me...
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Background: Minorities’ Diminished Returns (MDRs) refer to systemically weaker effects of socioeconomic status (SES) indicators on various developmental, behavioral, and health outcomes of ethnic minorities compared to non-Hispanic... more
Background: Minorities’ Diminished Returns (MDRs) refer to systemically weaker effects of socioeconomic status (SES) indicators on various developmental, behavioral, and health outcomes of ethnic minorities compared to non-Hispanic (non-Latino) Whites. Similar MDRs also exist for the effects of parental education on the school performance of ethnic minority youth. Aim: To assess whether regression toward the mean (RTM) has any role in explaining the diminished effects of parental education on the school performance of Black and Hispanic youth relative to non-Hispanic White youth. Materials and methods: Data for this cross-sectional study came from the Monitoring the Future survey (MTF, 2017), a nationally representative survey of American youth in 12th grade. The sample included 10,262 youth who were 12th graders (typically 17–18 years old). The independent variable was parental education with five categories: Some high school, High school graduate, Some college, College graduate, a...
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Background: Reward sensitivity (fun-seeking) is a risk factor for a wide range of high-risk behaviors. While high socioeconomic status (SES) is known to reduce reward sensitivity and associated high-risk behaviors, less is known about the... more
Background: Reward sensitivity (fun-seeking) is a risk factor for a wide range of high-risk behaviors. While high socioeconomic status (SES) is known to reduce reward sensitivity and associated high-risk behaviors, less is known about the differential effects of SES on reward sensitivity. It is plausible to expect weaker protective effects of family SES on reward sensitivity in racial minorities, a pattern called Minorities’ Diminished Returns (MDRs). Aim: We compared Caucasian and African American (AA) children for the effects of subjective family SES on children’s fun-seeking. Methods: This was a cross-sectional analysis of 7061 children from the Adolescent Brain Cognitive Development (ABCD) study. The independent variable was subjective family SES. The main outcome was children’s fun-seeking measured by the behavioral approach system (BAS) and behavioral avoidance system (BIS). Age, gender, marital status, and household size were the covariates. Results: In the overall sample, hi...
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Background: Racial minorities, particularly non-Hispanic blacks (NHBs) in the US, experience weaker effects from their families’ socioeconomic status on tangible outcomes, a pattern called the Minorities’ Diminished Returns (MDRs) theory.... more
Background: Racial minorities, particularly non-Hispanic blacks (NHBs) in the US, experience weaker effects from their families’ socioeconomic status on tangible outcomes, a pattern called the Minorities’ Diminished Returns (MDRs) theory. These MDRs are frequently shown in the effects of the families’ socioeconomic status (SES) on NHB adolescents’ school performance. As a result of these MDRs, NHB adolescents from high SES families show a worse than expected school performance. The existing knowledge is, however, minimal about the role of attention in explaining the diminished returns of the families’ SES with regard to the adolescents’ outcomes. Aim: To investigate the racial differences in the effects of the subjective family SES on adolescents’ attention, we compared non-Hispanic white (NHW) and NHB adolescents to assess the effect of the subjective family SES on adolescents’ attention. Methods: This was a cross-sectional analysis that included 4188 adolescents from the Adolescen...
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To investigate racial and ethnic differences in the protective effects of parental education and marital status against adolescents’ depressed mood and suicidal attempts in the U.S. As proposed by the Marginalization-related Diminished... more
To investigate racial and ethnic differences in the protective effects of parental education and marital status against adolescents’ depressed mood and suicidal attempts in the U.S. As proposed by the Marginalization-related Diminished Returns (MDRs), parental education generates fewer tangible outcomes for non-White compared to White families. Our existing knowledge is very limited regarding diminished returns of parental education and marital status on adolescents’ depressed mood and suicidal attempts. To compare racial groups for the effects of parental education and marital status on adolescents’ depressed mood and suicidal attempt. This cross-sectional study included 7076 non-Hispanic White or African American 8-11 years old adolescents from the Adolescent Brain Cognitive Development (ABCD) study. The independent variables were parental education and marital status. The main outcomes were depressed mood and suicidal attempts based on parents’ reports using the Kiddie Schedule f...
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Background: Brookings Institution has identified postponing childbirth from teenage to adulthood as a major strategy that is needed for upward social mobility of women. However, according to the Minorities’ Diminished Returns (MDRs), the... more
Background: Brookings Institution has identified postponing childbirth from teenage to adulthood as a major strategy that is needed for upward social mobility of women. However, according to the Minorities’ Diminished Returns (MDRs), the associations between aspirations, investments, behaviors, and socioeconomic position (SEP) may be diminished for marginalized groups such as African Americans. Objective: To extend the existing knowledge on the MDRs, the current study had two aims: First to compare White and African American women for the association between postponing childbearing to adulthood and SEP in a national sample of American women. Second, to test correlates of postponing childbearing to adulthood and SEP at birth with long term outcomes 15 years later when the child was 15 years old. Methods: For this longitudinal study, data came from the Fragile Families and Child Well-being Study (FFCWS), a national longitudinal prospective study in the United States (US) that followed...
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Background: Based on the Marginalization-related Diminished Returns (MDRs) framework, high socioeconomic status (SES) such as parental education shows weaker effects for Blacks than Whites. For example, high SES Black individuals report a... more
Background: Based on the Marginalization-related Diminished Returns (MDRs) framework, high socioeconomic status (SES) such as parental education shows weaker effects for Blacks than Whites. For example, high SES Black individuals report a high level of depression, anxiety, suicide, chronic disease, smoking, and mortality. Limited knowledge exists on MDRs of parental education on dietary behavior. Aims: Built on the MDRs framework, we tested the hypothesis of whether the effect of parental education on eating breakfast differs for Black compared to White families. We hypothesized that there is an association between mothers’ educational attainment and eating breakfast and compared Blacks and Whites for the effect of mothers’ educational attainment on the frequency of eating breakfast. Methods: The Fragile Families and Child Wellbeing Study is a 15-year follow up study of a random sample of births in cities larger than 200,000 population. The predictor was parental education at birth....
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Background: For African American middle-aged and older adults with hypertension, poor adherence to medication and lifestyle recommendations is a source of disparity in hypertension outcomes including higher rates of stroke in this... more
Background: For African American middle-aged and older adults with hypertension, poor adherence to medication and lifestyle recommendations is a source of disparity in hypertension outcomes including higher rates of stroke in this population relative to whites. Aims: To study demographic, social, behavioral, cognitive, and medical predictors of adherence to medication and lifestyle recommendations among underserved African American middle-aged and older adults with hypertension. Methods: This was a community-based cross-sectional survey in South Los Angeles with 338 African American middle-aged and older adults with hypertension who were 55 years or older. Age, gender, continuity of care, comorbidity, financial difficulty, self-rated health, depression, educational attainment, adherence knowledge, and adherence worries were the independent variables. Data was analyzed using linear regression with two outcomes, namely, adherence to medication (measured by the first 9 items of the Blo...
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Background. Although psychosocial and health factors impact insomnia symptoms, less is known about these effects in economically disadvantaged African-American older adults. Aims. This study investigated social and health determinants of... more
Background. Although psychosocial and health factors impact insomnia symptoms, less is known about these effects in economically disadvantaged African-American older adults. Aims. This study investigated social and health determinants of insomnia symptoms among economically disadvantaged African-American older adults. Methods. This survey enrolled 398 African-American older adults (age ≥ 65 years) from economically disadvantaged areas of South Los Angeles. Gender, age, educational attainment, financial difficulty, number of chronic diseases, self-rated health, pain intensity, and depression were covariates. Total insomnia, insomnia symptoms, and insomnia impact were our outcomes. Linear regression was applied for data analysis. Results. Based on linear regression, higher financial difficulty (B = 0.48, 95% CI = 0.35–0.61), smoking status (B = 1.64, 95% CI = 0.13–3.16), higher pain intensity (B = 0.39, 95% CI = 0.11–0.67), higher number of chronic diseases (B = 0.34, 95% CI = 0.05–0....
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Background: Although other mechanisms are also involved, at least one reason high educational attainment (EA) is associated with better health is lower employment stress in individuals with high EA. Minorities’ Diminished Returns,... more
Background: Although other mechanisms are also involved, at least one reason high educational attainment (EA) is associated with better health is lower employment stress in individuals with high EA. Minorities’ Diminished Returns, however, refer to the smaller protective health effects of EA for racial- and ethnic-minority individuals, particularly African Americans (AAs) and Hispanics, as compared to Whites. We are, however, not aware of many studies that have explored differential associations between EA and work-related stress across racial and ethnic groups. Aims: We aimed to compare racial and ethnic groups for the association between EA and occupational stress in a national sample of American adults. Methods: The National Health Interview Survey (NHIS 2015), a cross-sectional survey, included 15,726 employed adults. Educational attainment was the independent variable. Occupational stress was the outcome. Race and ethnicity were the moderators. Age, gender, number of jobs, and ...
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Background. Despite the prevalence of multimorbidity among African American (AA) older adults, little information exists on correlates of polypharmacy (using 5+ medications) in AA older adults. There is more information available... more
Background. Despite the prevalence of multimorbidity among African American (AA) older adults, little information exists on correlates of polypharmacy (using 5+ medications) in AA older adults. There is more information available regarding the link between polypharmacy and physical aspects of health than subjective ones. Aims. In a local sample of AA older adults in Los Angeles, this study investigated the association of polypharmacy with self-rated health (SRH) and depression. We also explored gender differences in these links. Methods. This community-based study was conducted in south Los Angeles. A total number of 708 AA older adults (age ≥ 55 years) were entered into this study. From this number, 253 were AA men and 455 were AA women. Polypharmacy was the independent variable. Self-rated health (SRH) and depression were the dependent variables. Age, educational attainment, financial difficulty (difficulty paying bills, etc.), and marital status were covariates. Gender was the mo...
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Background: Despite the association between polypharmacy and undesired health outcomes being well established, very little is known about epidemiology of polypharmacy in the African American community. We are not aware of any nationally... more
Background: Despite the association between polypharmacy and undesired health outcomes being well established, very little is known about epidemiology of polypharmacy in the African American community. We are not aware of any nationally representative studies that have described the socioeconomic, behavioral, and health determinants of polypharmacy among African Americans. Aims: We aimed to investigate the socioeconomic and health correlates of polypharmacy in a national sample of African American adults in the US. Methods: The National Survey of American Life (NSAL, 2003–2004) included 3,570 African American adults. Gender, age, socioeconomic status (SES; education attainment, poverty index, and marital status), access to the healthcare system (health insurance and having a usual source of care), and health (self-rated health [SRH], chronic medical disease, and psychiatric disorders) in addition to polypharmacy (5 + medications) as well as hyper-polypharmacy (10 + medications) were...
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Background: Compared to Whites, African Americans are at a higher risk of multiple chronic conditions, which places them at a higher risk of polypharmacy. Few national studies, however, have tested whether polypharmacy is associated with... more
Background: Compared to Whites, African Americans are at a higher risk of multiple chronic conditions, which places them at a higher risk of polypharmacy. Few national studies, however, have tested whether polypharmacy is associated with psychological distress—the net of socioeconomic status, health status, and stress—in African Americans. Aims: In a national sample of African Americans in the US, this study investigated the association between polypharmacy and psychological distress. Methods: The National Survey of American Life (NSAL, 2003) included 3570 African American adults who were 18 years or over. This number was composed of 2299 women and 1271 men. Polypharmacy (using ≥ 5 medications) and hyper-polypharmacy (using ≥ 10 medications) were the independent variables. Psychological distress was the dependent variable. Age, gender, socioeconomic status (education attainment, income, employment, and marital status), health care access (insurance status and usual place of care), a...
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Despite concerns about racial differences on adherence to prescribed medication rigimens among older adults, current information about nonadherence among underserved elderly African Americans with co-morbidities is limited. This study... more
Despite concerns about racial differences on adherence to prescribed medication rigimens among older adults, current information about nonadherence among underserved elderly African Americans with co-morbidities is limited. This study examines the association between adherence to drug regimens and an array of medication-related factors, including polypharmacy, medication regimen complexity, use of Potentially Inappropriate Medications (PIM), and knowledge about the therapeutic purpose and instructions of medication use. Four-hundred African Americans, aged 65 years and older, were recruited from South Los Angeles. Structured, face-to-face interviews and visual inspection of participants' medications were conducted. From the medication container labels, information including strength of the drug, expiration date, instructions, and special warnings were recorded. The Medication Regimen Complexity Index (MRCI) was measured to quantify multiple features of drug regimen complexity. T...
Research Interests: Health Literacy, Medication Adherence, Medicine, Multivariate Analysis, Humans, and 13 moreHospitalization, United States, Female, Male, Prescription drugs, African Americans, Clinical Sciences, Aged, Polypharmacy, Cross Sectional Studies, Regimen, Potentially inappropriate medication list, and Medical prescription
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Magma often contains elongated crystals, which are embedded in its viscous flow. In solidified magma bodies, one of the principal features observed in the field is the coherent arrangement of crystals or a net polarization of their... more
Magma often contains elongated crystals, which are embedded in its viscous flow. In solidified magma bodies, one of the principal features observed in the field is the coherent arrangement of crystals or a net polarization of their orientations in that segment. These arrangements are often observed as parallel to the dike or perpendicular to the sill or even at a very low angle to the edge of the inclined sheet. Such a structural arrangement is usually interpreted as the result of magma flow, which caused the crystals to rotate and align within direction of the flow. It was observed during experiments that while crystals rotate continually in a Couette-type shear flow, their major axis has a high probability and their minor axis has low probability to be aligned parallel to the flow direction. In this study, we present a new method of numerically modelling crystal rotation in different flow regimes. Having a large number of small crystals in complex flows can make the problem very e...
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Sheet intrusions supply magma to almost all eruptions. Mechanically, the erupting sheets are primarily extension fractures and of two main geometric types: dikes and inclined (cone) sheets. Regional dikes are mostly subvertical, many... more
Sheet intrusions supply magma to almost all eruptions. Mechanically, the erupting sheets are primarily extension fractures and of two main geometric types: dikes and inclined (cone) sheets. Regional dikes are mostly subvertical, many metres, occasionally tens of metres, thick, with strike dimensions (strike length) from kilometres to tens of kilometres (or more). By contrast, inclined sheets dip on average 30-40◦, are mostly less than one metre thick, and with strike dimension of hundreds of metres or, at most, a few kilometres. The density/frequency is also generally much greater in sheet swarms than in regional dike swarms. Forecasting the geometry and likely propagation path (including a possible eruption) of a sheet intrusion during volcanic unrest is of fundamental importance. The inferred geometry of the sheet is also an indication of the volume of magma that leaves the chamber during the unrest period. Sheet paths and geometries (including depth and opening/aperture) are comm...
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Summary Elongate inclusions immersed in a viscous fluid generally rotate at a rate that is different from the local angular velocity of the flow. Often, a net alignment of the inclusions develops, and the resulting shape preferred... more
Summary Elongate inclusions immersed in a viscous fluid generally rotate at a rate that is different from the local angular velocity of the flow. Often, a net alignment of the inclusions develops, and the resulting shape preferred orientation of the particle ensemble can then be used as a strain marker that allows reconstruction of the fluid’s velocity field. Much of the previous work on the dynamics of flow-induced particle rotations has focused on spatially homogeneous flows with large-scale tectonic deformations as the main application. Recently, the theory has been extended to spatially varying flows, such as magma with embedded crystals moving through a volcanic plumbing system. Additionally, an evolution equation has been introduced for the probability density function of crystal orientations. Here, we apply this new theory to a number of simple, 2-D flow geometries commonly encountered in magmatic intrusions, such as flow from a dyke into a reservoir or from a reservoir into ...
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Laboratory-based elastic wave measurements are commonly used to quantify the seismic properties of Earth’s crust and upper mantle. Different types of laboratory apparatuses are available for such measurements, simulating seismic... more
Laboratory-based elastic wave measurements are commonly used to quantify the seismic properties of Earth’s crust and upper mantle. Different types of laboratory apparatuses are available for such measurements, simulating seismic properties at different pressure and temperature. To complement such laboratory measurements, we present a numerical toolbox to investigate the seismic properties of rock samples. The numerical model is benchmarked against experimental results from a multi-anvil apparatus, using measurements of a stainless steel calibration standard. Measured values of the mean compressional- and shear-wave velocities at room conditions of the steel block were 6.03 km/s and 3.26 km/s, respectively. Calculated numerical results predicted 6.12 km/s and 3.30 km/s for compressional and shear-wave velocities. Subsequently, we measured Vp and Vs up to 600 MPa hydrostatic confining pressure and 600 °C. These measurements, at pressure and temperature, were then used as the basis to ...
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Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (for example, magma... more
Sea-level change is thought to influence the frequencies of volcanic eruptions on glacial to interglacial timescales. However, the underlying physical processes and their importance relative to other influences (for example, magma recharge rates) remain poorly understood. Here we compare an approximately 360-kyr-long record of effusive and explosive eruptions from the flooded caldera volcano at Santorini (Greece) with a high-resolution sea-level record spanning the last four glacial–interglacial cycles. Numerical modelling shows that when the sea level falls by 40 m below the present-day level, the induced tensile stresses in the roof of the magma chamber of Santorini trigger dyke injections. As the sea level continues to fall to −70 or −80 m, the induced tensile stress spreads throughout the roof so that some dykes reach the surface to feed eruptions. Similarly, the volcanic activity gradually disappears after the sea level rises above −40 m. Synchronizing Santorini’s stratigraphy with the sea-level record using tephra layers in marine sediment cores shows that 208 out of 211 eruptions (both effusive and explosive) occurred during periods constrained by sea-level falls (below −40 m) and subsequent rises, suggesting a strong absolute sea-level control on the timing of eruptions on Santorini—a result that probably applies to many other volcanic islands around the world. Sea-level lowstands over the last 360,000 years strongly controlled the timing of eruptions of the Santorini Volcano, according to an analysis of tephras and sea-level records, as well as numerical modelling of the underlying magma chamber.
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Background: Recent studies have shown that parental educational attainment is associated with a larger superior temporal cortical surface area associated with higher reading ability in children. Simultaneously, the marginalization-related... more
Background: Recent studies have shown that parental educational attainment is associated with a larger superior temporal cortical surface area associated with higher reading ability in children. Simultaneously, the marginalization-related diminished returns (MDRs) framework suggests that, due to structural racism and social stratification, returns of parental education are smaller for black and other racial/ethnic minority children compared to their white counterparts. Purpose: This study used a large national sample of 9–10-year-old American children to investigate associations between parental educational attainment, the right and left superior temporal cortical surface area, and reading ability across diverse racial/ethnic groups. Methods: This was a cross-sectional analysis that included 10,817 9–10-year-old children from the Adolescent Brain Cognitive Development (ABCD) study. Parental educational attainment was treated as a five-level categorical variable. Children’s right and...
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Residential treatment for alcoholism is associated with high completion rates for clients, yet there appear to be gender disparities in patient referrals and treatment completion rates. We studied whether (A) gender is associated with... more
Residential treatment for alcoholism is associated with high completion rates for clients, yet there appear to be gender disparities in patient referrals and treatment completion rates. We studied whether (A) gender is associated with differential patient placement to outpatient vs. residential treatment facilities and (B) completion rates differ by gender. In this cross-sectional study, we analyzed the admission and discharge data from 185 publicly funded substance abuse treatment facilities across Los Angeles County between 2005 and 2010. Among the 33,745 studied cases, women were referred to residential treatment facilities less frequently than men (75% vs. 66%). The adjusted results derived from logistic regression models confirmed that females were more likely to be referred to outpatient treatment than to residential treatment facilities (odds ratio [OR]: 1.15, 95% confidence interval [CI]: 1.05-1.26). In addition, we observed that compared to White/Caucasian patients, all oth...