- Palermo, Sicilia, Italy
- MEMS design: Sensors and Actuators, MEMS sensor, Mems Accelerometer, Earthquake Engineering, Earthquake, Earthquake Seismology, and 5 moreStructural Health Monitoring, vibration based methods for Structural Health Monitoring (SHM), Seismology, Seismology (Engineering), and Engineering Seismologyedit
In this paper, we propose the use of advanced and flexible statistical models to describe the spatial displacement of earthquake data. The paper aims to account for the external geological information in the description of complex seismic... more
In this paper, we propose the use of advanced and flexible statistical models to describe the spatial displacement of earthquake data. The paper aims to account for the external geological information in the description of complex seismic point processes, through the estimation of models with space varying parameters. A local version of the Log-Gaussian Cox processes (LGCP) is introduced and applied for the first time, exploiting the inferential tools in Baddeley (Spat Stat 22:261–295, 2017), estimating the model by the local Palm likelihood. We provide methods and approaches accounting for the interaction among points, typically described by LGCP models through the estimation of the covariance parameters of the Gaussian Random Field, that in this local version are allowed to vary in space, providing a more realistic description of the clustering feature of seismic events. Furthermore, we contribute to the framework of diagnostics, outlining suitable methods for the local context an...
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In this paper, we propose a novel picking algorithm for the automatic P- and S-waves onset time determination. Our algorithm is based on the variance piecewise constant models of the earthquake waveforms. The effectiveness and robustness... more
In this paper, we propose a novel picking algorithm for the automatic P- and S-waves onset time determination. Our algorithm is based on the variance piecewise constant models of the earthquake waveforms. The effectiveness and robustness of our picking algorithm are tested both on synthetic seismograms and real data. We simulate seismic events with different magnitudes (between 2 and 5) recorded at different epicentral distances (between 10 and 250 km). For the application to real data, we analyse waveforms from the seismic sequence of L’Aquila (Italy), in 2009. The obtained results are compared with those obtained by the application of the classic STA/LTA picking algorithm. Although the two algorithms lead to similar results in the simulated scenarios, the proposed algorithm results in greater flexibility and automation capacity, as shown in the real data analysis. Indeed, our proposed algorithm does not require testing and optimization phases, resulting potentially very useful in ...
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Multidisciplinary geophysical investigations have been carried out in a small area of the Greek archaeological site of Kamarina, in southern Sicily, in order to support some hypotheses, derived from historical and archaeological bases.... more
Multidisciplinary geophysical investigations have been carried out in a small area of the Greek archaeological site of Kamarina, in southern Sicily, in order to support some hypotheses, derived from historical and archaeological bases. After an aerial photographic and thermographic survey, a small area near to the Agora has been considered for magnetometric and GPR investigations. Obtained results show a good correlation and allow to highlight some structures oriented in agreement with the uncovered remains. The use of integrated geophysical techniques allowed a more robust interpretation of the detected anomalies in order to better address the choices for new excavations
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A technological system capable of automatically producing damage scenarios at an urban scale, as soon as an earthquake occurs, can help the decision-makers in planning the first post-disaster response, i.e., to prioritize the field... more
A technological system capable of automatically producing damage scenarios at an urban scale, as soon as an earthquake occurs, can help the decision-makers in planning the first post-disaster response, i.e., to prioritize the field activities for checking damage, making a building safe, and supporting rescue and recovery. This system can be even more useful when it works on densely populated areas, as well as on historic urban centers. In the paper, we propose a processing chain on a GIS platform to generate post-earthquake damage scenarios, which are based: (1) on the near real-time processing of the ground motion, that is recorded in different sites by MEMS accelerometric sensor network in order to take into account the local effects, and (2) the current structural characteristics of the built heritage, that can be managed through an information system from the local public administration authority. In the framework of the EU-funded H2020-ARCH project, the components of the system...
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Seismic networks are powerful tools for understanding active tectonic processes in a monitored region. Their numerous applications, from monitoring seismicity to characterizing seismogenic volumes and generated seismicity, make seismic... more
Seismic networks are powerful tools for understanding active tectonic processes in a monitored region. Their numerous applications, from monitoring seismicity to characterizing seismogenic volumes and generated seismicity, make seismic networks essential tools for assessing seismic hazard in active regions. The ability to locate earthquakes hypocenters requires a seismic network with a sufficient number of optimally distributed, stations. It is important to assess existing network geometry, to identify seismogenic volumes that are not adequately monitored, and to quantify measures that will allow network improvement. In this work we have studied the spatial arrangement of the stations of the Italian National Seismic Network by means of several Point Pattern techniques The results of the point patter analysis were compare with the spatial distribution of the historical and instrument seismicity and with the distribution of the well know seismogenetic sources of the Italian peninsula....
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Introduction. The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al., 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al., 2014) and to identify areas with similar seismic... more
Introduction. The use of HVSR technique allows in many cases (Bonnefoy-Claudet et al., 2006) to obtain detailed reconstruction of the roof of the seismic bedrock (Di Stefano et al., 2014) and to identify areas with similar seismic behaviour. Theoretical considerations (Nakamura, 1989) and experimental tests showed that amplification of horizontal motions between bottom and top of a sedimentary cover is well related to the ratio between the spectra of the horizontal and vertical components of the ground velocity (Nakamura, 2000). This ratio is a measure of ellipticity of Rayleigh wave polarization, overlooking Love and body waves contribution. Assuming that subsoil can be represented as a stack of homogeneous horizontal layers and imposing some geometric and/or physical constraints it is possible to estimate the parameters of the shear wave velocity model (Fäh et al., 2003; Parolai et al., 2000). The integration of data related to HVSR and active techniques based on the analysis of s...
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In the Sicily Channel, volcanic activity has been concentrated mainly on the Pantelleria and Linosa islands, while minor submarine volcanism took place in the Adventure, Graham and Nameless banks. The volcanic activity spanned mostly... more
In the Sicily Channel, volcanic activity has been concentrated mainly on the Pantelleria and Linosa islands, while minor submarine volcanism took place in the Adventure, Graham and Nameless banks. The volcanic activity spanned mostly during Plio-Pleistocene, however, historical submarine eruptions occurred in 1831 on the Graham Bank and in 1891 offshore Pantelleria Island. On the Graham Bank, 25 miles SW of Sciacca, the 1831 eruption formed the short-lived Ferdinandea Island that represents the only Italian volcano active in historical times currently almost completely unknown and not yet monitored. Moreover, most of the Sicily Channel seismicity is concentrated along a broad NS belt extending from the Graham Bank to Lampedusa Island. In 2012, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) carried out a multidisciplinary oceanographic cruise, named “Ferdinandea 2012”, the preliminary results of which represent the aim of this paper. The cruise goal was the mapping of the ...
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At 01:36 UTC (03:36 local time) on August 24th 2016, an earthquake Mw 6.0 struck an extensive sector of the central Apennines (coordinates: latitude 42.70° N, longitude 13.23° E, 8.0 km depth). The earthquake caused about 300 casualties... more
At 01:36 UTC (03:36 local time) on August 24th 2016, an earthquake Mw 6.0 struck an extensive sector of the central Apennines (coordinates: latitude 42.70° N, longitude 13.23° E, 8.0 km depth). The earthquake caused about 300 casualties and severe damage to the historical buildings and economic activity in an area located near the borders of the Umbria, Lazio, Abruzzo and Marche regions. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) located in few minutes the hypocenter near Accumoli, a small town in the province of Rieti. In the hours after the quake, dozens of events were recorded by the National Seismic Network (Rete Sismica Nazionale, RSN) of the INGV, many of which had a ML > 3.0. The density and coverage of the RSN in the epicentral area meant the epicenter and magnitude of the main event and subsequent shocks that followed it in the early hours of the seismic sequence were well constrained. However, in order to better constrain the localizations of the aftersho...
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The TOMO-ETNA experiment was planned in order to obtain a detailed geological and structural model of the continental and oceanic crust beneath Mt. Etna volcano and northeastern Sicily up to the Aeolian Islands (southern Italy), by... more
The TOMO-ETNA experiment was planned in order to obtain a detailed geological and structural model of the continental and oceanic crust beneath Mt. Etna volcano and northeastern Sicily up to the Aeolian Islands (southern Italy), by integrating data from active and passive refraction and reflection seismic methodologies, magnetic and gravity surveys. This paper focuses on the marine activities performed within the experiment, which have been carried out in the Ionian and Tyrrhenian Seas, during three multidisciplinary oceanographic cruises, involving three research vessels (“Sarmiento de Gamboa”, “Galatea” and “Aegaeo”) belonging to different countries and institutions. During the offshore surveys about 9700 air-gun shots were produced to achieve a high-resolution seismic tomography through the wide-angle seismic refraction method, covering a total of nearly 2650 km of shooting tracks. To register ground motion, 27 ocean bottom seismometers were deployed, extending the inland seismic...
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In this work, we propose a statistical approach to evaluate the coverage of a network based on the spatial distribution of its nodes and the target information, including all those data related to the final objectives of the network... more
In this work, we propose a statistical approach to evaluate the coverage of a network based on the spatial distribution of its nodes and the target information, including all those data related to the final objectives of the network itself. This statistical approach encompasses descriptive spatial statistics in combination with point pattern techniques. As case studies, we evaluate the spatial arrangements of the stations within the Italian National Seismic Network and the Italian Strong Motion Network. Seismic networks are essential tools for observing earthquakes and assessing seismic hazards, while strong motion (accelerometric) networks allow us to describe seismic shaking and to measure the expected effects on buildings and infrastructures. The capability of both networks is a function of an adequate number of optimally distributed stations. We compare the seismic network with the spatial distributions of historical and instrument seismicity and with the distribution of well-kn...
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In this paper we simulate a Unmanned Aerial Vehicle's (UAV) recognition after a possible case of diffuse damage after a seismic event in the town of Acireale (Sicily, Italy). Given a set of sites (84 relevant buildings) and the range... more
In this paper we simulate a Unmanned Aerial Vehicle's (UAV) recognition after a possible case of diffuse damage after a seismic event in the town of Acireale (Sicily, Italy). Given a set of sites (84 relevant buildings) and the range of the UAV, we are able to find the number of vehicles to employ and the shortest survey path. The problem of finding the shortest survey path is an operational research problem called Vehicle Routing Problem (VRP) whose solution is known to be computationally time-consuming. We used the Simulated Annealing (SA) heuristic that is able to provide stable solutions in relatively short computing time. We also examined the distribution of the cost of the solutions varying the depot on a regular grid in order to assess the best area where to execute the survey.
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Summary Several shallow submarines areas are characterized by considerable releases of hydrocarbon gases, which, during earthquakes or volcanic activity, may suddenly and violently occur. In some instances, changes in chemical and... more
Summary Several shallow submarines areas are characterized by considerable releases of hydrocarbon gases, which, during earthquakes or volcanic activity, may suddenly and violently occur. In some instances, changes in chemical and physical properties of gas emissions, which are generated by geothermal systems connected to the volcanoes’ plumbing system, are important precursors of volcanic activity and useful indices for the study of the geothermal field. Furthermore, some superficial structures such faults, landslide slopes or archaeological relics should be studied with such a high detail that geophysical and bathymetric surveys are unable to provide. In response to the needs increasingly felt of a completely customizable low cost tool for geological/geophysical/geochemical investigation of shallow submarine system, in the framework of the ROVER project, starting from an international project called OpenROV, is being implemented a micro-ROV for multidisciplinary environmental investigation. In this paper, we will describe the project progress, with particular reference to the first tests conducted in pool and in sea water, the geophysical/geochemical instrumentation of which will be equipped and the automatic control algorithms that are being developed for the semi-automatic navigation.
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We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of... more
We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of the optimal sites for the installation of the offshore stations, which is a crucial factor for the success of the monitoring campaign. In this paper, we propose a two steps automatic procedure for the identification of the best stations geometry. In the first step, based on the application of a set of a priori criteria, the suitable sites to host the ocean bottom seismic stations are identified. In the second step, the network improvement is evaluated for all the possible stations geometries by means of numerical simulation. The application of this procedure allows us to identify the best stations geometry to be achieved in the monitoring campaign.
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Research Interests: Earth Sciences, Geology, Seismology, Geosciences, Volcano, and 3 moreEtna, Seismic Noise, and Seismic Network
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In recent years, a detailed archeoseismological investigation has been carried out in the necropolis of Abakainon in order to identify traces of an ancient earthquake. Although the identification of seismic damage was undoubtedly... more
In recent years, a detailed archeoseismological investigation has been carried out in the necropolis of Abakainon in order to identify traces of an ancient earthquake. Although the identification of seismic damage was undoubtedly attributed to the 1st century AD earthquake, it was hypothesised that the level of damaging observed in the necropolis, as well as the counter slope tilting of the tomb basements may have also caused by a seismo-induced landslide, which produced locally an amplification of the seismic shaking. In order to identify the landslide, on which the Greek site lies, detailed geomorphological and geophysical surveys have been carried out. The research was directed to the acquisition of deep geological data for the reconstruction of slope process and the thickness of mobilised materials. The applied geophysical techniques included Seismic Refraction Tomography (SRT), Electrical Resistivity Tomography (ERT), microtremor analysis (HVSR). The surveys were performed in order to delineate the sliding surface and to assess approximatively the thickness of mobilised materials. The results coming from geomorphological data combined with and geophysical surveys confirm the presence of different overlapped landslides in the studied area.
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The ocean bottom seismometer with hydrophone deployed on the flat top of the Marsili submarine volcano (790 m deep) by the Gibilmanna OBS Lab (CNT-INGV) from 12th to 21st July, 2006, recorded more than 1000 transient seismic signals.... more
The ocean bottom seismometer with hydrophone deployed on the flat top of the Marsili submarine volcano (790 m deep) by the Gibilmanna OBS Lab (CNT-INGV) from 12th to 21st July, 2006, recorded more than 1000 transient seismic signals. Nineteen of these signals were associated with tectonic earthquakes: 1 teleseismic, 8 regional (located by INGV) and 10 small local seismic events (non located earthquakes). The regional events were used to determine sensor orientation. By comparing the signals recorded with typical volcanic seismic activity, we were able to group all the other signals into three categories: 817 volcano-tectonic type B (VT-B) events, 159 occurrences of high frequency tremor (HFT) and 32 short duration events (SDE). Small-magnitude VT-B swarms, having a frequency band of 2-6 Hz and a mean length of about 30 s, were almost all recorded during the first 7 days. During the last 2 days, the OBS/H mainly recorded HFT events with frequencies of over 40 Hz and of a few minutes in length. Signals that have similar features in frequency and time domain are generally associated with hydrothermal activity. During the last two days a signal was recorded that had a frequency content similar to that of VT-B events was recorded. It will be referred to as continuous volcanic tremor (CVT). The SDE signals, characterized by a quasi-monochromatic waveform and having an exponential decaying envelope, may have been generated by oscillations of resonant bodies excited by magmatic or hydrothermal activity. By applying polarization and parametric spectral analyses, we inferred that the VT-B were probably multi P-phase events having shallow sources that were situated in narrow azimuthal windows in relation to the positions of the OBS/H. The parametric spectral analysis of the SDE signals allowed us to determine their dominant complex frequencies with high accuracy; these frequencies are distributed in two distinct clusters on the complex plane.
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The Ocean Bottom Seismometer with Hydrophone (OBS/H) is an autonomous data-acquisition system which free falls to the sea floor to record seismic and pressure signals generated by earthquakes and tsunamis. The development and the... more
The Ocean Bottom Seismometer with Hydrophone (OBS/H) is an autonomous data-acquisition system which free falls to the sea floor to record seismic and pressure signals generated by earthquakes and tsunamis. The development and the improvement of OBS/H's is a necessary process for seismological research institutions, because in the world about 90 percent of all natural earthquakes has epicenters in offshore areas. This paper describes the OBS/H developed by the "Istituto Nazionale di Geofisica e Vulcanologia" (INGV), designed to reliably collect broadband data from seafloor sites during long term deployment. The data recorded by seismometers on the sea floor is influenced by background noise. In particular, the free fall of the instrument and the subsequent dropping of the seismic sensor on the superficial sediments, could cause coupling problems with signals distortion and high level noise due to the sensor tilt. Supported by data acquired during several monitoring campaigns in the Mediterranean Sea, we will show that the INGV OBS/H is able to record high quality seismic signals with low noise levels and low distortion, proving a good coupling of the seismometer with the seabed.
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A properly organized seismic network is a valuable tool for monitoring seismic zones and assessing seismic hazards. In this paper we propose a new method (seismic network evaluation through simulation, SNES) to evaluate the performance of... more
A properly organized seismic network is a valuable tool for monitoring seismic zones and assessing seismic hazards. In this paper we propose a new method (seismic network evaluation through simulation, SNES) to evaluate the performance of hypocenter location of a seismic network. The SNES method gives, as a function of magnitude, hypocentral depth, and confidence level, the spatial distribution of the number of active stations in the location procedure and their relative azimuthal gaps, along with confidence intervals in hypocentral parameters. The application of the SNES method also permits evaluation of the magnitude of completeness (M C), the background noise levels at the stations, and assessment of the appropriateness of the velocity model used in location routine. Italy sits on a tectonically active plate boundary at the convergence of the Eurasian and African lithospheric plates and has a high level of seismicity. In this paper, we apply the SNES method to the Italian National Seismic Network (Rete Sismica Nazionale Centralizzata dell'Istituto Nazionale di Geofisica e Vulcanologia, RSNC-INGV) which has monitored Italian seismicity since the early 1980s, following the destructive 1980 Irpinia earthquake. In recent years, the RSNC-INGV has grown significantly. In fact, in February 2010, it received signals from 305 seismic stations, 258 with wideband three-component sensors. We constructed SNES maps for magnitudes of 1.5, 2, 2.5, and 3, fixing the hypocentral depth at 10 km and the confidence level at 95%. Through the application of the SNES method, we show that the RSNC-INGV provides the best monitoring coverage in the Apennine Mountains with errors that for M 2, are less than 2 and 4 km for epicenter and hypocentral depth, respectively. At M 2.5 this seismic network is capable of constraining earthquake hypocenters to depths of about 150 km for most of the Italian Peninsula. This seismic network provides a threshold of completeness down to M 2 for almost the entire Italian territory.
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S U M M A R Y In this paper, we analyse the location performance of the Hellenic (Greek) Unified Seismolog-ical Network (HUSN) by Seismic Network Evaluation through Simulation method (SNES). This method gives, as a function of magnitude,... more
S U M M A R Y In this paper, we analyse the location performance of the Hellenic (Greek) Unified Seismolog-ical Network (HUSN) by Seismic Network Evaluation through Simulation method (SNES). This method gives, as a function of magnitude, hypocentral depth and confidence level, the spatial distribution of the: number of active stations in the location procedure and their relative azimuthal gaps and confidence intervals in hypocentral parameters regarding both the geometry of the seismic network and the use of an inadequate velocity model. Greece is located on a tectonically active plate boundary at the convergence of the Eurasian and African lithospheric plates and exhibits a high level of seismicity. The HUSN monitors the seismicity in Greek territory from 2007. At present it is composed by 88 seismic stations appropriately distribute in the area of Greece. The application of the SNES method permitted us to evaluate the background noise levels recorded by the network stations and estimate an empirical law that links the variance of P and S traveltime residuals to hypocentral distance. The statistical analysis of the P and S traveltime residuals allowed us to assess the appropriateness of the velocity model used by the HUSN in the location routine process. We constructed SNES maps for magnitudes (M L) of 2, 2.5 and 3, fixing the hypocentral depth to 10 km and the confidence level to 95 per cent. We also investigated, by two different vertical sections, the behaviour of the errors in hypocentral parameters estimates as function of depth. Finally, we also evaluated, fixing the hypocentral depth to 10 km and the confidence level to 95 per cent, the Magnitude of Completeness. Through the application of the SNES method, we demonstrate that the HUSN provides the best monitoring coverage in western Greece with errors, that for M L = 2.5, are less than 2 and 5 km for epicentre and hypocentral depth, respectively. At magnitude 2.5, this seismic network is capable of constraining earthquake hypocentres to depths of about 160 km and more, and provides a threshold of completeness down to magnitude 2 for most of Greek territory. We delineate some seismogenic areas of southern Greece that probably are not adequately covered by HUSN. Use of the SNES technique could optimize upgrades of the network in these areas.
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Romania is an earthquake prone area with a few destructive earthquakes per century. The National Institute for Earth Physics carries out the seismic survey of Romania through the Romanian National Seismic Network (RNSN) consisting of 65... more
Romania is an earthquake prone area with a few destructive earthquakes per century. The National Institute for Earth Physics carries out the seismic survey of Romania through the Romanian National Seismic Network (RNSN) consisting of 65 real-time seismic stations. Daily reports and monthly bulletins are delivered after routinely analyzing and processing the recorded data. In the present paper we applied the Seismic Network Evaluation through Simulation method for the RNSN configuration as it was in August 2011 to estimate the background noise level, assess the appropriateness of the velocity model adopted in routine location procedure, evaluate the hypocenter location uncertainty and determine the detection magnitude threshold. Areas of greater (southern Romania) and lower (Carpathians and Apuseni Mountains) background noise within the RNSN are identified by mapping the average power of noise in 1-12 Hz frequency range. The statistical study of the P and S phases residual times allow us to assess the appropriateness of the velocity model used in routine location. Both P-and S-wave velocity models can be optimized to improve the quality of the hypocenter location. As shown by our analysis, the RNSN is able to detect and locate earthquakes with M L magnitude above 2.5 anywhere on the Romanian territory, except the border areas, such as the Crisana-Maramures seismic source zone. Merging data from both sides of the border significantly improves the quality of hypocenter location in these areas.
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We apply the Seismic Network Evaluation through Simulation (SNES) method to evaluate the performance of the Alaska Regional Seismic Network (ARSN) in locating regional earthquakes in terms of validity of the velocity models, hypocen-tral... more
We apply the Seismic Network Evaluation through Simulation (SNES) method to evaluate the performance of the Alaska Regional Seismic Network (ARSN) in locating regional earthquakes in terms of validity of the velocity models, hypocen-tral errors, and magnitude of completeness. We find that background noise levels at the sites are highest in the Aleutian region and lowest in mainland Alaska. We demonstrate that the ARSN provides the best monitoring in the south-central region, with horizontal and vertical errors of less than 1.5 and 3 km, respectively, at the completeness level of M L 2.0. At the completeness level of M L 3.0, the network is capable of locating earthquakes for the whole region down to depths of about 250 km with satisfactory errors. The lowest magnitude completeness levels, of about 1.4 and even less, are achieved with satisfactory location errors in limited areas of the south-central region that have the densest station coverage. The network does not monitor the seismogenic areas in northern, western, southeastern, and offshore Alaska at an adequate level in terms of earthquake location errors. Network upgrades in these areas could be optimized using the SNES results.
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In this paper we introduce a simple procedure to identify clusters of multivariate waveforms based on a simultaneous assignation and alignment procedure. This approach is aimed at the identification of clusters of earthquakes, assuming... more
In this paper we introduce a simple procedure to identify clusters of multivariate waveforms based on a simultaneous assignation and alignment procedure. This approach is aimed at the identification of clusters of earthquakes, assuming that similarities between seismic events with respect to hypocentral parameters and focal mechanism correspond to similarities between waveforms of events. Therefore we define a distance measure between seismic curves in R d d Z 1, in order to interpret and better understand the main features of the generating seismic process.
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In this paper we analyze the location performance of the Montana Regional Seismic Network (MRSN) using the Seismic Network Evaluation through Simulation (SNES) method. Montana has a high level of seismicity that includes approximately... more
In this paper we analyze the location performance of the Montana Regional Seismic Network (MRSN) using the Seismic Network Evaluation through Simulation (SNES) method. Montana has a high level of seismicity that includes approximately 1500 locatable earthquakes annually. The MRSN comprises 38 stations deployed over an area of approximately 50,000 km 2. The application of the SNES method permits us to evaluate the background noise levels of the network stations and estimate an empirical law that links the variance of P and S travel-time residuals to hypocentral distance. This in turn permits us to assess the appropriateness of the velocity model used by the MRSN in the location routine. We constructed SNES maps for M L 1.4, 1.6, 1.8, 2.0, and 2.2, fixing the hypocentral depth at 10 km and at the 95% confidence level. Through application of the SNES method, we show that MRSN provides the best monitoring coverage in the Flathead Valley of northwestern Montana, with errors for M L 2 that are less than 2 and 6 km for epicenter and hypocentral depth, respectively. At magnitude 2.2, this seismic network is capable of locating earthquakes as deep as 150 km and provides a threshold of completeness down to magnitude 1.5 for most of western Montana. We delineate some seismogenic areas of western Montana, including the central portion of the centennial tectonic belt in extreme southwestern Montana, that are not adequately covered by the MRSN alone.
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Spain is a low-to-moderate seismicity area with relatively low seismic hazard. However, several strong shallow earthquakes have shaken the country causing casualties and extensive damage. Regional seismicity is monitored and surveyed by... more
Spain is a low-to-moderate seismicity area with relatively low seismic hazard. However, several strong shallow earthquakes have shaken the country causing casualties and extensive damage. Regional seismicity is monitored and surveyed by means of the Spanish National Seismic Network, maintenance and control of which are entrusted to the Instituto Geográfico Nacional. This array currently comprises 120 seismic stations distributed throughout Spanish territory (mainland and islands). Basically, we are interested in checking the noise conditions, reliability, and seismic detection capability of the Spanish network by analyzing the background noise level affecting the array stations , errors in hypocentral location, and detection threshold, which provides knowledge about network performance. It also enables testing of the suitability of the velocity model used in the routine process of earthquake location. To perform this study we use a method that relies on P and S wave travel times, which are computed by simulation of seismic rays from virtual seismic sources placed at the nodes of a regular grid covering the study area. Given the characteristics of the seismicity of Spain, we drew maps for M L magnitudes 2.0, 2.5, and 3.0, at a focal depth of 10 km and a confidence level 95 %. The results relate to the number of stations involved in the hypocentral location process, how these stations are distributed spatially, and the uncertainties of focal data (errors in origin time, longitude, latitude, and depth). To assess the extent to which principal seismogenic areas are well monitored by the network , we estimated the average error in the location of a seismic source from the semiaxes of the ellipsoid of confidence by calculating the radius of the equivalent sphere. Finally, the detection threshold was determined as the magnitude of the smallest seismic event detected at least by four stations. The northwest of the peninsula, the Pyrenees, especially the westernmost segment, the Betic Cordillera, and Tenerife Island are the best-monitored zones. Origin time and focal depth are data that are far from being constrained by regional events. The two Iberian areas with moderate seismicity and the highest seismic hazard, the Pyrenees and Betic Cordillera, and the northwestern quadrant of the peninsula, are the areas wherein the focus of an earthquake is determined with an approximate error of 3 km. For M L 2.5 and M L 3.0 this error is common for almost the whole peninsula and the Canary Islands. In general, errors in epicenter latitude and longitude are small for near-surface earthquakes, increasing gradually as the depth increases, but remaining close to 5 km even at a depth of 60 km. The hypocentral depth seems to be well constrained to a depth of 40 km beneath the zones with the highest density of stations, with an error of less than 5 km. The M L magnitude detection threshold of the network is approximately 2.0 for most of Spain and still less, almost 1.0, for the western sector of the Pyrenean region and the Canary Islands.
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Seismology and geodesy are generally seen as the most reliable diagnostic tools for monitoring highly active or erupting volcanoes, like Mt. Etna. From the early 1980's, seismic activity was monitored at Mt. Etna by a permanent seismic... more
Seismology and geodesy are generally seen as the most reliable diagnostic tools for monitoring highly active or erupting volcanoes, like Mt. Etna. From the early 1980's, seismic activity was monitored at Mt. Etna by a permanent seismic network, progressively improved in the following years. This network has been considerably enhanced since 2005 by 24-bit digital stations equipped with broad-band (40 s) sensors. Today, thanks to a configuration of 33 broad-band and 12 short-period stations, we have a good coverage of the volcanic area as well as a high quality of the collected data. In the framework of the VULCAMED project a work-group of Istituto Nazionale di Geofisica e Vulcanologia has taken on the task of developing the seismic monitoring system , through the installation of other seismic stations. The choice of optimal sites must be clearly made through a careful analysis of the geometry of the existing seismic network. In this paper, we applied the Seismic Network Evaluation through Simulation in order to evaluate the performance of the Etna Seismic Network before and after the addition of the stations in the candidate sites. The main advantage of the adopted method is that we can evaluate the improvement of the network before the actual installation of the stations. Our analysis has permitted to identify some critical issues of the current permanent seismic network related to the lack of stations in the southern sector of the volcano, which is nevertheless affected by a number of seismogenic structures. We have showed that the addition of stations at the candidate sites would greatly extend the coverage of the network to the south by significantly reducing the errors in the hypocenter parameters estimation.
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At the present time, micro-electro-mechanical system (MEMS) acceler-ometers seem to provide adequate sensitivity, noise level, and dynamic range to be applicable to earthquake strong-motion acquisition. The current common use of MEMS... more
At the present time, micro-electro-mechanical system (MEMS) acceler-ometers seem to provide adequate sensitivity, noise level, and dynamic range to be applicable to earthquake strong-motion acquisition. The current common use of MEMS accelerometers in the modern mobile phone may provide a new means to easily enormously increase the number of observations when a strong earthquake occurs. However, before utilizing the signals recorded by a device, like a mobile phone equipped with a low-cost three-axis MEMS accelerometer for any scientific purpose, it is important to verify that the signal collected provides reliable records of ground motion. In this paper, we have tested the LIS331DLH MEMS accelerometer installed in the iPhone mobile phone using a vibrating table and the EpiSensor FBA (force-balance accelerometer) ES-T as the reference sensor. Our tests show that, in the typical frequency and amplitude range of interest of earthquake engineering (0.2-20 Hz and 10-2000 mg, in which g is the standard gravity of acceleration, or 9:80665 m=s 2), the LIS331DLH MEMS accelerometer has excellent frequency and phase response, comparable with that of some standard FBAs produced for strong-motion seismology. The main drawback of the LIS331DLH MEMS accelerometer is its low sensitivity, due to the high level of instrumental self noise, and so it can be used effectively only to record moderate to strong earthquakes (M L > 5) near the epicentral area.
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The Calabrian Arc is an area of high seismic hazard, in the past often affected by destructive earthquakes. The seismicity of the Calabrian region is monitored by the Italian National Seismic Network integrated by the Calabrian Regional... more
The Calabrian Arc is an area of high seismic hazard,
in the past often affected by destructive earthquakes. The
seismicity of the Calabrian region is monitored by the Italian
National Seismic Network integrated by the Calabrian Regional
one and, in the last three years, by the Pollino temporary
array. We have applied the Seismic Network Evaluation
through Simulation to assess the individual contribution of
each network in locating earthquakes with epicentres in the
Calabrian region and surrounding. We shows that the Calabrian
Regional Seismic Network greatly improves the quality
of the coverage in almost the Calabria territory except in
the Crotone Basin, in the Serre and in the offshore areas. We
show that the contribution of the Pollino temporary array is
instead restricted to a very small area centred on the Pollino
Chain. Due to the presence in the Serre of important seismogenic
volumes, which in the past have generated destructive
earthquakes, it would be opportune to add at least several
seismic stations in this area and surrounding to improve the
seismic monitoring.
in the past often affected by destructive earthquakes. The
seismicity of the Calabrian region is monitored by the Italian
National Seismic Network integrated by the Calabrian Regional
one and, in the last three years, by the Pollino temporary
array. We have applied the Seismic Network Evaluation
through Simulation to assess the individual contribution of
each network in locating earthquakes with epicentres in the
Calabrian region and surrounding. We shows that the Calabrian
Regional Seismic Network greatly improves the quality
of the coverage in almost the Calabria territory except in
the Crotone Basin, in the Serre and in the offshore areas. We
show that the contribution of the Pollino temporary array is
instead restricted to a very small area centred on the Pollino
Chain. Due to the presence in the Serre of important seismogenic
volumes, which in the past have generated destructive
earthquakes, it would be opportune to add at least several
seismic stations in this area and surrounding to improve the
seismic monitoring.
In 2009 December, the OBSLab-INGV (Istituto Nazionale di Geofisica e Vulcanologia) deployed an Ocean Bottom Seismometer with Hydrophone (OBS/H) near the epicentral area of the main shock of the Palermo seismic sequence of 2002. The... more
In 2009 December, the OBSLab-INGV (Istituto Nazionale di Geofisica e Vulcanologia) deployed an Ocean Bottom Seismometer with Hydrophone (OBS/H) near the epicentral area of the main shock of the Palermo seismic sequence of 2002. The monitoring activity had a total duration of about 8 months. During this experiment, the OBS/H recorded 247 very local microearthquakes, whose local magnitude is between −0.5 and 2.5 and T S − T P delay time between 0.2 and 5 s, almost all of which were undetected by the Italian National Seismic Network. This local microseismicity has been analysed using an innovative clustering technique that exploits the similarity between the waveforms generated by different events. The clustering technique implemented, based on hierarchical agglomerative algorithms, nearest neighbour technique and dendrogram representation, allowed us to identify nine distinct multiplets characterized by a high degree of similarity between the waveforms. The microevents were located through an improved single-station location (SSL) technique based on the polarization analysis of the 3C signals and on the estimation of the T S − T P time. In the new SSL technique, an unbiased covariance matrix was defined and a ray tracer-based determination of the epicentral distance and hypocentral depth was proposed. All the multiplets were generated by events with hypocentres that were very close to each other. However, not all the identified clusters are also clustered in the time-magnitude domain. It was also observed that some multiplets have clouds of hypocentres overlapping each other. These clusters, indistinguishable without the application of a waveforms clustering technique, show differences in the waveforms that must be attributed to differences in the focal mechanisms which generated the waveforms. The local seismic events recorded are typical of a seismicity generated by a volume characterized by a highly complex fracturing pattern and by an important role in the dynamics of fluid systems that, given the great depth of some multiplets, could come from the mantle. This picture is in agreement with the geometric characterization of the Palermo 2002 seismogenic volume.
Research Interests:
The absolute orientation of the horizontal components of ocean bottom or downhole seismic sensors are generally unknown. Almost all the methods proposed to overcome this issue are based on the post-processing of the acquired signals and... more
The absolute orientation of the horizontal components of ocean bottom or downhole seismic sensors are generally unknown. Almost all the methods proposed to overcome this issue are based on the post-processing of the acquired signals and so the results are strongly dependent on the nature, quantity and quality of the acquired data. We have carried out several test to evaluate the ability of retrieve sensor orientation using integrated low cost MEMS gyroscope. Our tests have shown that the tested MEMS gyroscope (the model 1044_0-3/3/3 Phidget Spatial Precision High Resolution) can be used to measure angular displacement and therefore to retrieve the absolute orientation of the horizontal components of a sensor that has been subjected to rotation in the horizontal plane. A correct processing of the acquired signals permit to retrieve, for rotation at angular rate between 0 and 180 • s −1 , angular displacement with error less 2 • .
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This study examines the temporal variation of the seismicity in the Val d'Agri (southern Italy) and adjacent areas , for the current seismic hazard evaluation. The temporal variation of the seismicity is expressed as time series of the... more
This study examines the temporal variation of the seismicity in the Val d'Agri (southern Italy) and adjacent areas , for the current seismic hazard evaluation. The temporal variation of the seismicity is expressed as time series of the number of earthquakes, b value of Gutenberg-Richter relationship or b value of the frequency-magnitude distribution and the seismic energy released in the form of logE 2/3. The analysis was performed by means of a new research tool that includes visualizing techniques, which helps the interactive exploration and the interpretation of temporal variation changes. The obtained time series show a precursory seismic-ity pattern, characterized by low and high probability periods , which preceded earthquakes of magnitude M ≥ 4.0. The 75 % of the examined cases were successfully correlated with a change in seismicity pattern. The average duration of the low and the high probability periods is 10.6 and 13.8 months respectively. These results indicate that the seismicity temporal variation monitoring in a given area and the recognition of the low and high probability periods can contribute to the evaluation, in regular monthly intervals, of current seismic hazard status.
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In this paper, we introduce a project for the realization of the first European real-time urban seismic network based on Micro Electro-Mechanical Systems (MEMS) technology. MEMS accelerometers are a highly enabling technology , and... more
In this paper, we introduce a project for the realization of the first European real-time urban seismic network based on Micro Electro-Mechanical Systems (MEMS) technology. MEMS accelerometers are a highly enabling technology , and nowadays, the sensitivity and the dynamic range of these sensors are such as to allow the recording of earthquakes of moderate magnitude even at a distance of several tens of kilometers. Moreover, thanks to their low cost and smaller size, MEMS accelerometers can be easily installed in urban areas in order to achieve an urban seismic network constituted by high density of observation points. The network is being implemented in the Acireale Municipality (Sicily, Italy), an area among those with the highest hazard, vulnerability and exposure to the earthquake of the Italian territory. The main objective of the implemented urban network will be to achieve an effective system for post-earthquake rapid disaster assessment. The earthquake recorded, also that with moderate magnitude will be used for the effective seismic microzonation of the area covered by the network. The implemented system will be also used to realize a site-specific earthquakes early warning system.
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We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of... more
We plan to deploy in the Taranto Gulf some Ocean Bottom broadband Seismometer with Hydrophones. Our aim is to investigate the offshore seismicity of the Sibari Gulf. The seismographic network optimization consists in the identification of the optimal sites for the installation of the offshore stations, which is a crucial factor for the success of the monitoring campaign. In this paper, we propose a two steps automatic procedure for the identification of the best stations geometry. In the first step, based on the application of a set of a priori criteria, the suitable sites to host the ocean bottom seismic stations are identified. In the second step, the network improvement is evaluated for all the possible stations geometries by means of numerical simulation. The application of this procedure allows us to identify the best stations geometry to be achieved in the monitoring campaign.
Research Interests:
At 01:36 UTC (03:36 local time) on August 24th 2016, an earthquake Mw 6.0 struck an extensive sector of the central Apennines (coordinates: latitude 42.70° N, longitude 13.23° E, 8.0 km depth). The earthquake caused about 300 casualties... more
At 01:36 UTC (03:36 local time) on August 24th 2016, an earthquake Mw 6.0 struck an extensive sector of the central Apennines (coordinates: latitude 42.70° N, longitude 13.23° E, 8.0 km depth). The earthquake caused about 300 casualties and severe damage to the historical buildings and economic activity in an area located near the borders of the Umbria, Lazio, Abruzzo and Marche regions. The Istituto Nazionale di Geof-isica e Vulcanologia (INGV) located in few minutes the hypocenter near Accumoli, a small town in the province of Rieti. In the hours after the quake, dozens of events were recorded by the National Seismic Network (Rete Sismica Nazionale, RSN) of the INGV, many of which had a ML > 3.0. The density and coverage of the RSN in the epicentral area meant the epicenter and magnitude of the main event and subsequent shocks that followed it in the early hours of the seismic sequence were well constrained. However, in order to better constrain the localizations of the aftershock hypocenters, especially the depths, a denser seismic monitoring network was needed. Just after the mainshock, SISMIKO, the coordinating body of the emergency seismic network at INGV, was activated in order to install a temporary seismic network integrated with the existing permanent network in the epicentral area. From August the 24th to the 30th, SISMIKO deployed eighteen seismic stations, generally six components (equipped with both velocimeter and accelerometer), with thirteen of the seismic station transmitting in real-time to the INGV seismic monitoring room in Rome. The design and geometry
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A geophysical study by means of electrical resistivity and induced polarization tomographies was carried out in the landfill site of Bellolampo (Palermo, Italy) to check the integrity of the landfill liner and to detect possible leachate... more
A geophysical study by means of electrical resistivity and induced polarization tomographies was carried out in the landfill site of Bellolampo (Palermo, Italy) to check the integrity of the landfill liner and to detect possible leachate plumes. Preliminarily, synthetic tests were performed, simulating acquisition data along profiles placed above resistivity distribution, suitable to represent landfills protected with an high-density polyethylene (HDPE) liner at the bottom or with possible leachate plumes. Optimized array data sets for parallel measurements have been tested in order to assess the resolution and the effectiveness of tomographic images, comparing inversions with and without the constraint of the HDPE liner position. Based on the obtained results, three electrical tomographies have been planned and carried out directly over the landfill and nearby. The results provided useful information for identifying the electrical properties of the rock, waste, and leachate; for identifying snags and disruption of the tank bottom liner; and for pointing out possible polluting leachate nearby and below the landfill.
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Please cite this article in press as: D'Alessandro, A., et al., Evidence for serpentinization of the Ionian upper mantle from simultaneous inversion of P-and S-wave arrival times. J. Geodyn. (2016), http://dx. Keywords: Ocean bottom... more
Please cite this article in press as: D'Alessandro, A., et al., Evidence for serpentinization of the Ionian upper mantle from simultaneous inversion of P-and S-wave arrival times. J. Geodyn. (2016), http://dx. Keywords: Ocean bottom seismometer Minimum 1D velocity model Ionian basin Upper mantle serpentinization a b s t r a c t Simultaneous inversion of P-and S-wave arrival times, collected during a 3-years Ocean Bottom Seis-mometer with Hydrophone (OBS/H) monitoring campaign, yields 1D P-and S-wave velocity models for the Ionian lithosphere (Central Mediterranean). The 1D model highlights the presence, in the Ionian upper mantle, of two layers characterized by high seismic P-wave velocity (S1 and S2, 6.3-6.7 and 7.5 km/s, respectively). These two layers, with thicknesses of about 3.3 km and 5 km, respectively, and ranging from ∼8 to ∼16 km in depth, are characterized by low S-wave velocity (S1 = 3.05-3.2 km/s, S2 = 3.85 km/s) and high values of V P /V S (S1 = 2.06-2.09, S2 = 1.95). This is a characteristic feature, often encountered in passive margins and is generally interpreted as partly serpentinized peridotite. The V P , V S and V P /V S values of S1 are consistent with 55-65% of serpentinization of the upper mantle, while the S2 ones are consistent with 15-25% of serpentinization. This research provides a crucial hint about the debated nature of the Ionian crust, suggesting its oceanic structure.