Continental carbonates, such as travertines and tufas, formed from CO2-rich groundwater degassing... more Continental carbonates, such as travertines and tufas, formed from CO2-rich groundwater degassing as it emerges at the Earth’s surface, are often associated with major crustal-scale faults. The Carraclaca site, in the Lorca-Totana section of the Alhama de Murcia Fault, Spain, presents a complex geomorphological landscape controlled by active tectonics. The geology here records the interaction between Quaternary alluvial fans, travertines, and a pop-up structure developed in a transpressional section of the fault. The Alhama de Murcia Fault is an 80 km long left-lateral strike-slip fault that is one of the main seismogenic structures in the Iberian Peninsula. In this work, we examined the relation between travertine precipitation in the Carraclaca site and the tectonic activity of this fault zone through morphological and geochemical studies. The δ13C and δ18O isotopic signals indicate that the carbonate deposits are hydrothermal. In addition, the 87Sr/86Sr ratios in the samples sugg...
El Salvador is located at the pacific active margin of Central America, here, the subduction of t... more El Salvador is located at the pacific active margin of Central America, here, the subduction of the Cocos Plate under the Caribbean Plate with a rate of ca. 80 mm/yr is the main seismic source. However, the relative eastward drift of the Caribbean plate induces deformations within the Central American Volcanic Arc, and active faults within it have been responsible of several damaging earthquakes in El Salvador.
Historical earthquakes are of major importance in the analysis of seismic hazards, in particular ... more Historical earthquakes are of major importance in the analysis of seismic hazards, in particular for stable continental regions. In this article, we propose a methodology that uses seismic scenarios to provide constraints on the location of the seismic source of historical earthquakes. Our methodology involves generating seismic scenarios for the proposed seismic sources and comparing the results to the observed intensity field of the earthquake. To avoid the bias related to strongly heterogeneously distributed datasets, we focus on data points that are useful in discriminating between competing ruptures. These data are identified by the spatial patterns of residuals between seismic scenarios produced for each source. We apply this methodology to a test event—the 1999 Athens earthquake—for which both the magnitude and location are constrained by independent data, and to the 1909 Benavente earthquake, for which the magnitude is constrained by seismological studies, but the location i...
The El Salvador Fault Zone (ESFZ) is part of the Central American Volcanic Arc and accommodates t... more The El Salvador Fault Zone (ESFZ) is part of the Central American Volcanic Arc and accommodates the oblique separation movement between the forearc sliver and the Chortis block (Caribbean Plate). In this work, a triclinic transtension model was applied to geological (fault-slip inversion, shape of volcanic calderas), seismic (focal mechanisms) and geodetic (GPS displacements) data to evaluate the characteristics of the last stages of the kinematic evolution of the arc. The El Salvador Fault Zone constitutes a large band of transtensional deformation whose direction varies between N90° E and N110° E. Its dip is about 70° S because it comes from the reactivation of a previous extensional stage. A protocol consisting of three successive steps was followed to compare the predictions of the model with the natural data. The results show a simple shear direction plunging between 20° and 50° W (triclinic flow) and a kinematic vorticity number that is mostly higher than 0.81 (simple-shearing...
How to cite Complete issue More information about this article Journal's homepage in redalyc... more How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System
We present a map and a data set containing information about intra-plate seismic sources in El Sa... more We present a map and a data set containing information about intra-plate seismic sources in El Salvador. These are the results of the field campaigns and data analysis carried out by the research group of Planetary Geodinamics, Active Tectonics and Related Risks from Complutense University of Madrid during the last 12 years. We include two maps, the first map contains 1405 fault traces with evidences of Quaternary activity derived form morphometric, paleoseismological and geomorphological analysis together with field data mapping carried in El Salvador. The second map is a synthesis of the 29 intra-plate seismic sources selected from the quaternary faults map. The geometry of these sources was simplified and we also include a table where some available data of the proposed sources are included, such as their name, orientation, length and slip-rate. For further interpretation and discussion of these sources see (Alonso-Henar et al., 2018) [1, doi.org/10.1016/j.enggeo.2018.06.015].
<p>Estimating the rate and the pattern of active deformation of slow-slip s... more <p>Estimating the rate and the pattern of active deformation of slow-slip structures in intracontinental regions has always been a challenging task. Central Portugal is one of those intracontinental regions where the convergence of Eurasian and Nubian plates governs its active deformation. The NE-striking Lower Tagus Valley (LTV) is a locus of active deformation and several historical earthquakes. The eastern and western margins of the LTV are fault-controlled zones (Lower Tagus Valley Fault Zone; LTVFZ), characterized by the predominant strike-slip component. The ~80 km long LTVFZ is one of the most significant intraplate structures in mainland Portugal, and its seismic activity may pose a considerable threat in densely populated urban and industrial areas developed along the LTV. However, the spatio-temporal seismic history along the main structures of LTV is still poorly constrained. In this study, we investigate the geomorphologic features along the Eastern LTVFZ using high-resolution digital aerial orthophotos, high-resolution topographic data extracted from airborne Light Detection and Ranging (LiDAR) data sets, drone-derived high-resolution topographic data, and very high-resolution orthophotos acquired by a small unoccupied aerial system. Removing vegetation cover by LiDAR data leads to access to bare earth surface models that are essential to recognize subtle geomorphic features and constrain their offsets. Accordingly, several cumulative left-lateral displacements were measured along a 20-km stretch of the Eastern LTVFZ. The smallest measured offsets range between 2 and 3 meters that may correspond to the coseismic slip during the most recent surface faulting.     </p><p>To specify the contribution of the Eastern LTVFZ to the regional seismic hazard, we investigate its seismic history through three paleoseismic trenches excavated across the fault near the city of Almeirim. The stratigraphic units, structural features, and geological relations were first logged in the field and then evaluated using the high-resolution, rectified seamless trench-wall photomosaics. Several vertical to steep fault strands exposed in the trench walls cut through the late Pleistocene and Holocene alluvial deposits, recording the signature of several strong paleoearthquakes. Stratigraphic analysis and optically stimulated luminescence dating suggest that the most recent surface faulting has occurred sometime in the middle-late Holocene. The horizontal displacement of this earthquake was measured at two localities nearby the trench site, both in the field and on the very high-resolution orthophotos, and amounts to 2 to 3 meters of the on-fault sinistral offset. The evidence of an older earthquake has been preserved in the late marine isotope stage (MIS) 3 deposits, and at least two even older earthquakes recorded in a sequence of alluvial deposits that predate MIS 4. Although the Eastern LTVFZ may be characterize by low slip rates and instrumentally a quiescent structure, it remains capable of generating morphogenic large-magnitude earthquakes of Mw 7 to 7.5 with millennial recurrence intervals. Such seismic behavior challenges the reliability of assessing seismic hazard over slow-slipping faults across intraplate settings in the lack of geological information.</p>
Over the last ~15 years we have excavated 73 trenches across active normal faults in the Taupo an... more Over the last ~15 years we have excavated 73 trenches across active normal faults in the Taupo and Hauraki Rifts, North Island, New Zealand. The stratigraphy in these trenches is quite similar because of the predominance of volcanic and volcanic-derived deposits, sourced from the active Taupo Volcanic Zone. These deposits, whether alluvial (reworked, mainly volcanics) or volcanic (tephra), are all
Trabajo presentado en el XIII Congreso Geologico de America Central, celebrado en San Salvador (E... more Trabajo presentado en el XIII Congreso Geologico de America Central, celebrado en San Salvador (El Salvador) del 5 al 9 de junio de 2017
The Lower Tagus Valley Fault, Portugal, has long been associated with the damaging earthquakes th... more The Lower Tagus Valley Fault, Portugal, has long been associated with the damaging earthquakes that affected the Greater Lisbon Area in historical times. These include a poorly documented earthquake that occurred in 1344, the relatively well-documented 1531 earthquake, and the most recent M6.0 1909 earthquake. In this work, we use a 0.5 m resolution LiDAR-based digital elevation model and a 0.5 cm resolution digital surface model based on UAV photogrammetry to accurately locate the fault scarps in the northernmost portion of the western fault strand and to select sites to perform paleoseimolological investigations. The paleoseismological and geochronological analysis performed in the Alviela trench site document the fault activity in the last 3000 years, including two earthquakes during historical times. We performed ground motion scenarios for 20 km, 40 km, and 60 km ruptures including the trench site. The ground motion fields obtained for the 40 km and 60 km ruptures are in agreem...
Este trabajo propone un modelo cinemático 3D de la confluencia de las placas tectónicas Norteamer... more Este trabajo propone un modelo cinemático 3D de la confluencia de las placas tectónicas Norteamericana y Pacífica con las placas de Rivera y Cocos, centrado en la zona de convergencia de la Fosa Mesoamericana en el área de México. A partir del análisis de más de 1300 mecanismos focales de terremotos (M ≥ 5.5) obtenidos de la base de datos en abierto del programa Global Centroid-Moment-Tensor (CMT), se han aplicado diversas técnicas de geología estructural para obtener la distribución espacial de los tensores de deformación (ey, ex, ez) y del factor de forma (k’) de dichos tensores. Estas técnicas consisten en el estudio de los Diedros Rectos de los mecanismos focales y de la aplicación del Modelo de Deslizamiento, basados en la cinemática del deslizamiento sobre el plano de falla teórico asociado a cada sismo. Este análisis permite realizar un estudio tridimensional de la deformación mediante el agrupamiento espacial 3D de los diferentes tensores (análisis cluster), agrupando zonas ...
During the last years, several crustal seismic sources have been proposed in El Salvador; however... more During the last years, several crustal seismic sources have been proposed in El Salvador; however, the actual destructive potential of these proposals has not been revealed yet. Here we present several seismic scenarios related with the main crustal faults in the country. We have characterized the corresponding hazard scenarios in a deterministic way, estimating the peak ground accelerations (PGA) including local site effects. In addition, we present a list of 29 sources that can be considered potentially dangerous with their main features when they are available and four seismic scenarios that we consider to be more probable. We have resorted to the February 13th 2001 Mw 6.6 destructive earthquake, the only earthquake occurred in a known crustal source in El Salvador and recorded by the strong motion network, in order to test the methodological approach and the reliability of the PGA results predicted by two available Ground Motion Prediction Equations (GMPEs) including the site ef...
Continental carbonates, such as travertines and tufas, formed from CO2-rich groundwater degassing... more Continental carbonates, such as travertines and tufas, formed from CO2-rich groundwater degassing as it emerges at the Earth’s surface, are often associated with major crustal-scale faults. The Carraclaca site, in the Lorca-Totana section of the Alhama de Murcia Fault, Spain, presents a complex geomorphological landscape controlled by active tectonics. The geology here records the interaction between Quaternary alluvial fans, travertines, and a pop-up structure developed in a transpressional section of the fault. The Alhama de Murcia Fault is an 80 km long left-lateral strike-slip fault that is one of the main seismogenic structures in the Iberian Peninsula. In this work, we examined the relation between travertine precipitation in the Carraclaca site and the tectonic activity of this fault zone through morphological and geochemical studies. The δ13C and δ18O isotopic signals indicate that the carbonate deposits are hydrothermal. In addition, the 87Sr/86Sr ratios in the samples sugg...
El Salvador is located at the pacific active margin of Central America, here, the subduction of t... more El Salvador is located at the pacific active margin of Central America, here, the subduction of the Cocos Plate under the Caribbean Plate with a rate of ca. 80 mm/yr is the main seismic source. However, the relative eastward drift of the Caribbean plate induces deformations within the Central American Volcanic Arc, and active faults within it have been responsible of several damaging earthquakes in El Salvador.
Historical earthquakes are of major importance in the analysis of seismic hazards, in particular ... more Historical earthquakes are of major importance in the analysis of seismic hazards, in particular for stable continental regions. In this article, we propose a methodology that uses seismic scenarios to provide constraints on the location of the seismic source of historical earthquakes. Our methodology involves generating seismic scenarios for the proposed seismic sources and comparing the results to the observed intensity field of the earthquake. To avoid the bias related to strongly heterogeneously distributed datasets, we focus on data points that are useful in discriminating between competing ruptures. These data are identified by the spatial patterns of residuals between seismic scenarios produced for each source. We apply this methodology to a test event—the 1999 Athens earthquake—for which both the magnitude and location are constrained by independent data, and to the 1909 Benavente earthquake, for which the magnitude is constrained by seismological studies, but the location i...
The El Salvador Fault Zone (ESFZ) is part of the Central American Volcanic Arc and accommodates t... more The El Salvador Fault Zone (ESFZ) is part of the Central American Volcanic Arc and accommodates the oblique separation movement between the forearc sliver and the Chortis block (Caribbean Plate). In this work, a triclinic transtension model was applied to geological (fault-slip inversion, shape of volcanic calderas), seismic (focal mechanisms) and geodetic (GPS displacements) data to evaluate the characteristics of the last stages of the kinematic evolution of the arc. The El Salvador Fault Zone constitutes a large band of transtensional deformation whose direction varies between N90° E and N110° E. Its dip is about 70° S because it comes from the reactivation of a previous extensional stage. A protocol consisting of three successive steps was followed to compare the predictions of the model with the natural data. The results show a simple shear direction plunging between 20° and 50° W (triclinic flow) and a kinematic vorticity number that is mostly higher than 0.81 (simple-shearing...
How to cite Complete issue More information about this article Journal's homepage in redalyc... more How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System
We present a map and a data set containing information about intra-plate seismic sources in El Sa... more We present a map and a data set containing information about intra-plate seismic sources in El Salvador. These are the results of the field campaigns and data analysis carried out by the research group of Planetary Geodinamics, Active Tectonics and Related Risks from Complutense University of Madrid during the last 12 years. We include two maps, the first map contains 1405 fault traces with evidences of Quaternary activity derived form morphometric, paleoseismological and geomorphological analysis together with field data mapping carried in El Salvador. The second map is a synthesis of the 29 intra-plate seismic sources selected from the quaternary faults map. The geometry of these sources was simplified and we also include a table where some available data of the proposed sources are included, such as their name, orientation, length and slip-rate. For further interpretation and discussion of these sources see (Alonso-Henar et al., 2018) [1, doi.org/10.1016/j.enggeo.2018.06.015].
<p>Estimating the rate and the pattern of active deformation of slow-slip s... more <p>Estimating the rate and the pattern of active deformation of slow-slip structures in intracontinental regions has always been a challenging task. Central Portugal is one of those intracontinental regions where the convergence of Eurasian and Nubian plates governs its active deformation. The NE-striking Lower Tagus Valley (LTV) is a locus of active deformation and several historical earthquakes. The eastern and western margins of the LTV are fault-controlled zones (Lower Tagus Valley Fault Zone; LTVFZ), characterized by the predominant strike-slip component. The ~80 km long LTVFZ is one of the most significant intraplate structures in mainland Portugal, and its seismic activity may pose a considerable threat in densely populated urban and industrial areas developed along the LTV. However, the spatio-temporal seismic history along the main structures of LTV is still poorly constrained. In this study, we investigate the geomorphologic features along the Eastern LTVFZ using high-resolution digital aerial orthophotos, high-resolution topographic data extracted from airborne Light Detection and Ranging (LiDAR) data sets, drone-derived high-resolution topographic data, and very high-resolution orthophotos acquired by a small unoccupied aerial system. Removing vegetation cover by LiDAR data leads to access to bare earth surface models that are essential to recognize subtle geomorphic features and constrain their offsets. Accordingly, several cumulative left-lateral displacements were measured along a 20-km stretch of the Eastern LTVFZ. The smallest measured offsets range between 2 and 3 meters that may correspond to the coseismic slip during the most recent surface faulting.     </p><p>To specify the contribution of the Eastern LTVFZ to the regional seismic hazard, we investigate its seismic history through three paleoseismic trenches excavated across the fault near the city of Almeirim. The stratigraphic units, structural features, and geological relations were first logged in the field and then evaluated using the high-resolution, rectified seamless trench-wall photomosaics. Several vertical to steep fault strands exposed in the trench walls cut through the late Pleistocene and Holocene alluvial deposits, recording the signature of several strong paleoearthquakes. Stratigraphic analysis and optically stimulated luminescence dating suggest that the most recent surface faulting has occurred sometime in the middle-late Holocene. The horizontal displacement of this earthquake was measured at two localities nearby the trench site, both in the field and on the very high-resolution orthophotos, and amounts to 2 to 3 meters of the on-fault sinistral offset. The evidence of an older earthquake has been preserved in the late marine isotope stage (MIS) 3 deposits, and at least two even older earthquakes recorded in a sequence of alluvial deposits that predate MIS 4. Although the Eastern LTVFZ may be characterize by low slip rates and instrumentally a quiescent structure, it remains capable of generating morphogenic large-magnitude earthquakes of Mw 7 to 7.5 with millennial recurrence intervals. Such seismic behavior challenges the reliability of assessing seismic hazard over slow-slipping faults across intraplate settings in the lack of geological information.</p>
Over the last ~15 years we have excavated 73 trenches across active normal faults in the Taupo an... more Over the last ~15 years we have excavated 73 trenches across active normal faults in the Taupo and Hauraki Rifts, North Island, New Zealand. The stratigraphy in these trenches is quite similar because of the predominance of volcanic and volcanic-derived deposits, sourced from the active Taupo Volcanic Zone. These deposits, whether alluvial (reworked, mainly volcanics) or volcanic (tephra), are all
Trabajo presentado en el XIII Congreso Geologico de America Central, celebrado en San Salvador (E... more Trabajo presentado en el XIII Congreso Geologico de America Central, celebrado en San Salvador (El Salvador) del 5 al 9 de junio de 2017
The Lower Tagus Valley Fault, Portugal, has long been associated with the damaging earthquakes th... more The Lower Tagus Valley Fault, Portugal, has long been associated with the damaging earthquakes that affected the Greater Lisbon Area in historical times. These include a poorly documented earthquake that occurred in 1344, the relatively well-documented 1531 earthquake, and the most recent M6.0 1909 earthquake. In this work, we use a 0.5 m resolution LiDAR-based digital elevation model and a 0.5 cm resolution digital surface model based on UAV photogrammetry to accurately locate the fault scarps in the northernmost portion of the western fault strand and to select sites to perform paleoseimolological investigations. The paleoseismological and geochronological analysis performed in the Alviela trench site document the fault activity in the last 3000 years, including two earthquakes during historical times. We performed ground motion scenarios for 20 km, 40 km, and 60 km ruptures including the trench site. The ground motion fields obtained for the 40 km and 60 km ruptures are in agreem...
Este trabajo propone un modelo cinemático 3D de la confluencia de las placas tectónicas Norteamer... more Este trabajo propone un modelo cinemático 3D de la confluencia de las placas tectónicas Norteamericana y Pacífica con las placas de Rivera y Cocos, centrado en la zona de convergencia de la Fosa Mesoamericana en el área de México. A partir del análisis de más de 1300 mecanismos focales de terremotos (M ≥ 5.5) obtenidos de la base de datos en abierto del programa Global Centroid-Moment-Tensor (CMT), se han aplicado diversas técnicas de geología estructural para obtener la distribución espacial de los tensores de deformación (ey, ex, ez) y del factor de forma (k’) de dichos tensores. Estas técnicas consisten en el estudio de los Diedros Rectos de los mecanismos focales y de la aplicación del Modelo de Deslizamiento, basados en la cinemática del deslizamiento sobre el plano de falla teórico asociado a cada sismo. Este análisis permite realizar un estudio tridimensional de la deformación mediante el agrupamiento espacial 3D de los diferentes tensores (análisis cluster), agrupando zonas ...
During the last years, several crustal seismic sources have been proposed in El Salvador; however... more During the last years, several crustal seismic sources have been proposed in El Salvador; however, the actual destructive potential of these proposals has not been revealed yet. Here we present several seismic scenarios related with the main crustal faults in the country. We have characterized the corresponding hazard scenarios in a deterministic way, estimating the peak ground accelerations (PGA) including local site effects. In addition, we present a list of 29 sources that can be considered potentially dangerous with their main features when they are available and four seismic scenarios that we consider to be more probable. We have resorted to the February 13th 2001 Mw 6.6 destructive earthquake, the only earthquake occurred in a known crustal source in El Salvador and recorded by the strong motion network, in order to test the methodological approach and the reliability of the PGA results predicted by two available Ground Motion Prediction Equations (GMPEs) including the site ef...
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