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8 results on '"Institute of Engineering Seismology and Earthquake Engineering (ITSAK)"'

1. Wavefield characteristics and spatial incoherency - a comparative study from Argostoli rock- and soil-site dense seismic arrays

Author

Angkeara Svay, Fabrice Hollender, Pierre-Yves Bard, Nikos Theodoulidis, Afifa Imtiaz, Cécile Cornou, Vincent Perron, Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), CEA-Direction des Energies (ex-Direction de l'Energie Nucléaire) (CEA-DES (ex-DEN)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut des Sciences de la Terre (ISTerre), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019]), Institut des Sciences de la mécanique et Applications industrielles (IMSIA - UMR 9219), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-Centre National de la Recherche Scientifique (CNRS)-Université Paris-Saclay-EDF R&D (EDF R&D), EDF (EDF)-EDF (EDF), ITSAK, ANR-11-RSNR-0022,SINAPS@,Séisme et Installation Nucléaire -Améliorer et Pérenniser la Sûreté(2011), CEA-DEN Cadarache (CEA-DEN), CEA ISTerre, Affiliation nécessaire..., Laboratoire de mécanique des sols, structures et matériaux (MSSMat), CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Institute of Engineering Seismology (ITSAK), Institute of Engineering Seismology, CEA-Direction de l'Energie Nucléaire (CEA-DEN), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), SINAPS@ ANR-11-RSNR-0022,SINAPS@,SINAPS@: Séisme & Installations Nucléaires: Assurer et Pérenniser la Sûreté, Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École Nationale Supérieure de Techniques Avancées (ENSTA Paris)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-EDF R&D (EDF R&D), Institut des Sciences de la Terre [2016-2019] (ISTerre [2016-2019]), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes [2016-2019] (UGA [2016-2019])-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR), and Institute of Engineering Seismology and Earthquake Engineering (ITSAK)

Subjects
Diffraction, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], 0211 other engineering and technologies, 02 engineering and technology, 010502 geochemistry & geophysics, Spatial Coherency, 01 natural sciences, Cephalonia, [PHYS.MECA.MEMA]Physics [physics]/Mechanics [physics]/Mechanics of materials [physics.class-ph], symbols.namesake, [SPI]Engineering Sciences [physics], Geochemistry and Petrology, Dense Array, Wavefield characteristics, Rayleigh wave, Slowness, 0105 earth and related environmental sciences, [PHYS.MECA.VIBR]Physics [physics]/Mechanics [physics]/Vibrations [physics.class-ph], 021110 strategic, defence & security studies, Ranging, [PHYS.MECA.ACOU]Physics [physics]/Mechanics [physics]/Acoustics [physics.class-ph], Current (stream), [SPI.GCIV]Engineering Sciences [physics]/Civil Engineering, Geophysics, Rock Site, Surface wave, Parametric model, symbols, Sedimentary rock, [SPI.GCIV.DV]Engineering Sciences [physics]/Civil Engineering/Dynamique, vibrations, [SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing, Geology, Seismology
Abstract

International audience; The current article presents the results from the analysis of the seismic events recorded from a dense array located on a rock site at Argostoli, Cephalonia Island, Greece. The objective of the study is to explore to what extent the non-direct, diffracted surface waves influence the seismic wavefield at a rock site, to investigate the loss of coherency of ground motions and to compare the results with those from a previously studied similar array located at an adjacent small, shallow sedimentary valley. The array consists of 21 velocimeters encompassing a central station in four concentric circles with diameters 20, 60, 180 and 360 m. The analyzed seismic dataset includes 40 events with magnitudes ranging from 2 to 5 and epicentral distance up to 200 km. MUSIQUE algorithm has been used to analyze the seismic wavefield by extracting the backazimuth and slowness of the dominant incoming waves and identifying the Love and Rayleigh waves. Lagged coherency has been estimated for all the available station pairs in the array and the results from the entire dataset have been averaged at four separation distance intervals, 10-20, 20-30, 30-40, 80-90 m. The results were also compared with those from a similar array located on an adjacent small, shallow sedimentary valley. The analysis suggests that about 20percent energy of the wavefield could be characterized as diffracted Love and Rayleigh waves, primarily arriving from the north-east and north-south directions, respectively. The spatial coherency estimations at the rock site are, generally, observed to be larger than those from the sedimentary array, especially at frequencies below 5 Hz. The directionality of coherency estimates observed from the soil array is absent in case of the rock array data. Comparison with the widely-quoted parametric models reveals that there is little correlation between the decay of coherency observed at the rock site and the models. The significant difference observed between the results of the rock and soil array indicate that the spatial incoherency is largely site dependent and could be potentially associated with the formation of locally generated wavefield

Published
2018
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2. Near-source high-rate GPS, strong motion and InSAR observations to image the 2015 Lefkada (Greece) Earthquake rupture history

Author

Cristiano Tolomei, Antonella Cirella, Nikos Theodoulidis, Athanassios Ganas, Pierre Briole, Alessio Piatanesi, Daniele Cheloni, Antonio Avallone, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Institute of Engineering Seismology and Earthquake Engineering (ITSAK), Laboratoire de géologie de l'ENS (LGENS), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), National Observatory of Athens (NOA), Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Laboratoire de géologie de l'ENS (LGE), and École normale supérieure - Paris (ENS Paris)-École normale supérieure - Paris (ENS Paris)

Subjects
[SDU.STU.TE]Sciences of the Universe [physics]/Earth Sciences/Tectonics, Multidisciplinary, 010504 meteorology & atmospheric sciences, Science, Rake, Transform fault, Slip (materials science), 010502 geochemistry & geophysics, Geodesy, 01 natural sciences, Article, Tectonics, Rise time, Interferometric synthetic aperture radar, Seismic moment, Medicine, Earthquake rupture, ComputingMilieux_MISCELLANEOUS, Geology, 0105 earth and related environmental sciences
Abstract

The 2015/11/17 Lefkada (Greece) earthquake ruptured a segment of the Cephalonia Transform Fault (CTF) where probably the penultimate major event was in 1948. Using near-source strong motion and high sampling rate GPS data and Sentinel-1A SAR images on two tracks, we performed the inversion for the geometry, slip distribution and rupture history of the causative fault with a three-step self-consistent procedure, in which every step provided input parameters for the next one. Our preferred model results in a ~70° ESE-dipping and ~13° N-striking fault plane, with a strike-slip mechanism (rake ~169°) in agreement with the CTF tectonic regime. This model shows a bilateral propagation spanning ~9 s with the activation of three main slip patches, characterized by rise time and peak slip velocity in the ranges 2.5–3.5 s and 1.4–2.4 m/s, respectively, corresponding to 1.2–1.8 m of slip which is mainly concentrated in the shallower (0 = 1.05 × 1019 N m) suggest a magnitude of M w 6.6. Our best solution suggests that the occurrence of large (M w > 6) earthquakes to the northern and to the southern boundaries of the 2015 causative fault cannot be excluded.

Published
2017
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3. Close to the lair of Odysseus Cyclops: the SINAPS@ post- seismic campaign and accelerometric network installation on Kefalonia island

Author

HOLLENDER, Fabrice, Perron, Vincent, Imtiaz, Afifa, Svay, Angkeara, Mariscal, Armand, Bard, Pierre-Yves, Cottereau, Régis, Lopez-Caballero, Fernando, Cushing, Marc, Theodoulidis, Nikos, Moiriat, Denis, CEA Cadarache, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut des Sciences de la Terre (ISTerre), Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Laboratoire de mécanique des sols, structures et matériaux (MSSMat), CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Institute of Engineering Seismology and Earthquake Engineering (ITSAK), and AFPS / IFSTTAR

Subjects
cohérence, champ d'onde, wavefield, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], réseau vertical, post-seismic, Post-sismique, réseau dense, vertical array, Argostoli, coherency, rotatiomètre, dense array, rotatiometer
Abstract

International audience; The Koutavos-Argostoli (Kefalonia, Greece) site was selected within the ANR-PIA SINAPS@ project (www.institut-seism.fr/projets/sinaps/) to host a vertical accelerometricarray. The long term goal is to validate 3D nonlinear numerical simulation codes. This article shortly presents the site and its geodynamic, geological and seismic backgrounds, the borehole instrumentation and the associated geotechnical information, and the first results of the post-seismic campaign organized following the seismic sequence of January-February 2014 including two M6 + shocks and numerous aftershocks.; Le site d'Argostoli-Koutavos (Céphalonie, Grèce) a été sélectionné dans le cadre du projet ANR-PIA SINAPS@ (www.institut-seism.fr/projets/sinaps/) pour faire l'objet d'une instrumentation longue durée en réseau accélérométrique vertical. Le but à long terme est de valider les codes de simulation numérique 3D non-linéaires. Cet article présente brièvement le site et son contexte géodynamique, géologique et sismique, l'instrumentation en forage et les informations géotechniques associées, ainsi que les premiers résultats de la campagne post-sismiqueorganisée à la suite de la séquence sismique de janvier-février 2014, comprenant deux chocs de magnitude M6+ et de très nombreuses répliques.

Published
2015

4. A deux pas du repaire du Cyclope d'Ulysse: la campagne post-sismique et le démarrage du réseau accélérométrique SINAPS@ sur l'île de Céphalonie

Author

Fabrice Hollender, Vincent Perron, Afifa Imtiaz, Angkeara Svay, Armand Mariscal, Pierre-Yves Bard, Régis Cottereau, Fernando Lopez-Caballero, Marc Cushing, Nikos Theodoulidis, Denis Moiriat, CEA Cadarache, Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Institut des Sciences de la Terre (ISTerre), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Bureau de Recherches Géologiques et Minières (BRGM) (BRGM), Laboratoire de mécanique des sols, structures et matériaux (MSSMat), CentraleSupélec-Centre National de la Recherche Scientifique (CNRS), Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Institute of Engineering Seismology and Earthquake Engineering (ITSAK), AFPS / IFSTTAR, and Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
cohérence, champ d'onde, wavefield, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], réseau vertical, post-seismic, Post-sismique, réseau dense, vertical array, Argostoli, coherency, rotatiomètre, dense array, rotatiometer
Abstract

International audience; The Koutavos-Argostoli (Kefalonia, Greece) site was selected within the ANR-PIA SINAPS@ project (www.institut-seism.fr/projets/sinaps/) to host a vertical accelerometricarray. The long term goal is to validate 3D nonlinear numerical simulation codes. This article shortly presents the site and its geodynamic, geological and seismic backgrounds, the borehole instrumentation and the associated geotechnical information, and the first results of the post-seismic campaign organized following the seismic sequence of January-February 2014 including two M6 + shocks and numerous aftershocks.; Le site d'Argostoli-Koutavos (Céphalonie, Grèce) a été sélectionné dans le cadre du projet ANR-PIA SINAPS@ (www.institut-seism.fr/projets/sinaps/) pour faire l'objet d'une instrumentation longue durée en réseau accélérométrique vertical. Le but à long terme est de valider les codes de simulation numérique 3D non-linéaires. Cet article présente brièvement le site et son contexte géodynamique, géologique et sismique, l'instrumentation en forage et les informations géotechniques associées, ainsi que les premiers résultats de la campagne post-sismiqueorganisée à la suite de la séquence sismique de janvier-février 2014, comprenant deux chocs de magnitude M6+ et de très nombreuses répliques.

Published
2015

5. Observation of the spread of slow deformation in Greece following the breakup of the slab

Author

Virginie Durand, Michael Floyd, Nikos Theodulidis, Hayrullah Karabulut, David Marsan, Michel Bouchon, Jean Schmittbuhl, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), Mécanique des failles, Institut des Sciences de la Terre (ISTerre), Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry]), Department of Earth, Atmospheric and Planetary Sciences [MIT, Cambridge] (EAPS), Massachusetts Institute of Technology (MIT), Institute of Engineering Seismology and Earthquake Engineering (ITSAK), Kandilli Observatory and Earthquake Research Institute (KOERI), Boğaziçi University [Istanbul], Institut de physique du globe de Strasbourg (IPGS), Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Ecole et Observatoire des Sciences de la Terre (EOST), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Institut de Physique du Globe de Paris (IPG Paris)-Centre National de la Recherche Scientifique (CNRS), Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-PRES Université de Grenoble-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-Centre National de la Recherche Scientifique (CNRS), Boǧaziçi üniversitesi = Boğaziçi University [Istanbul], Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS), Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF)-Université Grenoble Alpes (UGA)-Centre National de la Recherche Scientifique (CNRS)-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])-PRES Université de Grenoble-Institut de recherche pour le développement [IRD] : UR219-Institut national des sciences de l'Univers (INSU - CNRS)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Université Joseph Fourier - Grenoble 1 (UJF), Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Strasbourg (UNISTRA)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Subduction, Eurasian Plate, Storm, [PHYS.PHYS.PHYS-GEO-PH]Physics [physics]/Physics [physics]/Geophysics [physics.geo-ph], Geophysics, Slip (materials science), Geodynamics, Breakup, 13. Climate action, Large earthquakes, Slab, General Earth and Planetary Sciences, ComputingMilieux_MISCELLANEOUS, Seismology, Geology
Abstract

International audience; Over the past two decades, geophysical observations have shown that earthquakes can trigger other earthquakes, raising the possibility that earthquake interaction plays an important role in the earth's deformation. We analyze here a "storm" of earthquakes in Greece and show that their interaction provides remarkable insight into the mechanics of one of the fastest deforming continental region in the world. A rupture of the African slab initiates a cascade of large earthquakes and a long episode of slow slip marking the downward plunge of the slab, the concomitant rollback of the subduction, and the subsequent detachment of southern Greece from the Eurasian plate. Intense crustal deformation, indicative of the resulting plate stretching, follows. This slow deformation which spreads in a few months over more than 500 km lasts~3 years and triggers earthquakes. The observations also show that the retreat of the African subduction is the motor of the Aegean deformation.

Published
2014
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6. Statistical correlation of earthquake and ambient noise spectral ratios

Author

Pierre-Yves Bard, H. Cadet, Valerio De Rubeis, Giovanna Cultrera, Nikos Theodoulidis, Istituto Nazionale di Geofisica e Vulcanologia - Sezione di Roma (INGV), Istituto Nazionale di Geofisica e Vulcanologia, Institute of Engineering Seismology and Earthquake Engineering (ITSAK), Institut des Sciences de la Terre (ISTerre), and Centre National de la Recherche Scientifique (CNRS)-PRES Université de Grenoble-Université Joseph Fourier - Grenoble 1 (UJF)-Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux (IFSTTAR)-Institut national des sciences de l'Univers (INSU - CNRS)-Institut de recherche pour le développement [IRD] : UR219-Université Savoie Mont Blanc (USMB [Université de Savoie] [Université de Chambéry])

Subjects
Basis (linear algebra), Frequency band, [SDU.STU.GP]Sciences of the Universe [physics]/Earth Sciences/Geophysics [physics.geo-ph], Ambient noise level, Building and Construction, Fundamental frequency, Geotechnical Engineering and Engineering Geology, Cross-validation, Correlation, Noise, Geophysics, Statistics, Canonical correlation, Civil and Structural Engineering, Mathematics
Abstract

International audience; The Horizontal-to-Vertical Spectral Ratio from earthquake (HVSR) and from ambient noise (HVN) recordings realistically indicate the fundamental frequency of soil response but, for the majority of the worldwide examined sites, they do not provide reliable amplification curves as calculated by the earthquake standard Spectral Ratio (SSR). Given the fact that HVSR and especially HVN can be easily obtained, it is challenging to search for a meaningful correlation with SSR amplification functions for the entire frequency band and to use the results for the SSR estimate at a further site where only noise measurements are available. To this aim we used recordings from 75 sites worldwide and we applied a multivariate statistical approach (canonical correlation analysis) to investigate and quantify any correlation among spectral ratios. The canonical correlation between SSR and HVN is then used to estimate the expected SSR at each site by a weighted average of the SSR values measured at the other sites; the weights are properly set to account more for sites with similar behaviour in terms of the canonical correlation results between HVN and SSR. This procedure, repeated for all sites in turn, constitutes the basis of a cross validation. The comparison between the inferred and the original SSR highlights the improvements of site response estimation with respect to the use of ambient noise techniques. The goodness and limitations of the reconstruction procedure are explained by specific geological settings.

Published
2014
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7. A Low-Cost Instrumentation System for Seismic Hazard Assessment in Urban Areas.

Author

Papanikolaou VK, Karakostas CZ, and Theodoulidis NP

Abstract

The development and application of a low-cost instrumentation system for seismic hazard assessment in urban areas are described in the present study. The system comprises a number of autonomous triaxial accelerographs, designed and manufactured in house and together with dedicated software for device configuration, data collection and further postprocessing. The main objective is to produce a detailed view of strong motion variability in urban areas, for at least light intensity strong motion events. The overall cost of the developed devices is at least ten times lower than the respective commercial units, hence their deployment as an ultra-dense network over the area of interest can be significantly cost-effective. This approach is considered an efficient complement to traditional microzonation procedures, which are typically based on relatively few actual recordings and the application of theoretical methodologies to assess the strong motion distribution. The manufactured devices adopt micro-electro-mechanical (MEMS) digital sensor technology for recording acceleration, whereas the accompanying software suite provides various configuration options, quick browsing, analyzing and exporting of the recorded events, as well as GIS type functionality for seamlessly producing explicit seismic hazard maps of the considered area. The evaluation of system performance was based on shaking table and real field comparisons against high accuracy commercial accelerographs. The study concludes with a real application of the proposed system in the form of an ultra-dense network installed at the city of Lefkada, an earthquake prone urban area in Greece, and the following compilation of explicit shakemaps.

Published
2021
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8. Near-source high-rate GPS, strong motion and InSAR observations to image the 2015 Lefkada (Greece) Earthquake rupture history.

Author

Avallone A, Cirella A, Cheloni D, Tolomei C, Theodoulidis N, Piatanesi A, Briole P, and Ganas A

Abstract

The 2015/11/17 Lefkada (Greece) earthquake ruptured a segment of the Cephalonia Transform Fault (CTF) where probably the penultimate major event was in 1948. Using near-source strong motion and high sampling rate GPS data and Sentinel-1A SAR images on two tracks, we performed the inversion for the geometry, slip distribution and rupture history of the causative fault with a three-step self-consistent procedure, in which every step provided input parameters for the next one. Our preferred model results in a ~70° ESE-dipping and ~13° N-striking fault plane, with a strike-slip mechanism (rake ~169°) in agreement with the CTF tectonic regime. This model shows a bilateral propagation spanning ~9 s with the activation of three main slip patches, characterized by rise time and peak slip velocity in the ranges 2.5-3.5 s and 1.4-2.4 m/s, respectively, corresponding to 1.2-1.8 m of slip which is mainly concentrated in the shallower (<10 km) southern half of the causative fault. The inferred slip distribution and the resulting seismic moment (M 0  = 1.05 × 10 19 N m) suggest a magnitude of M w 6.6. Our best solution suggests that the occurrence of large (M w  > 6) earthquakes to the northern and to the southern boundaries of the 2015 causative fault cannot be excluded.

Published
2017
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