Papers by Stéphane Gaffet
EGS General Assembly Conference Abstracts, 2002
Many observations and studies as well as numerical simulations have been done in order to complet... more Many observations and studies as well as numerical simulations have been done in order to completely understand the whole seismogram recorded during an earthquake. At regional distances, the seismic wavefield is strongly influenced by crustal hetero- geneities. The primary wavefield constituted by Pn, Pg, Sn, Sg, Rg, Lg.... phases is diffracted and refracted by these heterogeneities and hence forms the
HAL (Le Centre pour la Communication Scientifique Directe), 1998
A long sequence of earthquakes, six with magnitudes between 5 and 6, struck Central Italy startin... more A long sequence of earthquakes, six with magnitudes between 5 and 6, struck Central Italy starting on September 26, 1997, causing severe damages and loss of human lives. The seismogenic structure consists of a NW-SE elongated fault zone extending for about 40 km. The focal mechanisms of the largest shocks reveal normal faulting with NE-SW extension perpendicular to the trend of the Apennines, consistently with the Quaternary tectonic setting of the internal sector of the belt and with previous earthquakes in adjacent regions. Preliminary data on the main shocks and aftershocks show that extension in this region of the Apennines is accomplished by normal faults dipping at low angle (•40 ø) to the southwest, and confined in the upper •8 km of the crust. These normal faults might have reactivated thrust planes of the Pliocene compressional tectonics. The aftershock distribution and the damage patterns also suggest that the three main shocks ruptured distinct 5 to 15 km-long fault segments, adjacent and slightly offset from one another.
EGS General Assembly Conference Abstracts, 2002
Many observations and studies as well as numerical simulations have been done in order to complet... more Many observations and studies as well as numerical simulations have been done in order to completely understand the whole seismogram recorded during an earthquake. At regional distances, the seismic wavefield is strongly influenced by crustal hetero- geneities. The primary wavefield constituted by Pn, Pg, Sn, Sg, Rg, Lg.... phases is diffracted and refracted by these heterogeneities and hence forms the
AGU Fall Meeting Abstracts, Dec 1, 2016
HAL (Le Centre pour la Communication Scientifique Directe), 1998
A long sequence of earthquakes, six with magnitudes between 5 and 6, struck Central Italy startin... more A long sequence of earthquakes, six with magnitudes between 5 and 6, struck Central Italy starting on September 26, 1997, causing severe damages and loss of human lives. The seismogenic structure consists of a NW-SE elongated fault zone extending for about 40 km. The focal mechanisms of the largest shocks reveal normal faulting with NE-SW extension perpendicular to the trend of the Apennines, consistently with the Quaternary tectonic setting of the internal sector of the belt and with previous earthquakes in adjacent regions. Preliminary data on the main shocks and aftershocks show that extension in this region of the Apennines is accomplished by normal faults dipping at low angle (•40 ø) to the southwest, and confined in the upper •8 km of the crust. These normal faults might have reactivated thrust planes of the Pliocene compressional tectonics. The aftershock distribution and the damage patterns also suggest that the three main shocks ruptured distinct 5 to 15 km-long fault segments, adjacent and slightly offset from one another.
AGU Fall Meeting Abstracts, Dec 1, 2016
EGSGA, 2002
A temporary seismic network was installed in Central Chile (30rS-32rS), from the coast to the And... more A temporary seismic network was installed in Central Chile (30rS-32rS), from the coast to the Andes Cordillera, in order to study the seismotectonic characteristics of the flat-slab zone segment of the Nazca plate. At the zone, the subduction beneath the South America plate takes place with a convergence rate of 8 cm/yr. The local seis- micity was recorded from Nov.
EGSGA, 2002
A temporary seismic network was installed in Central Chile (30rS-32rS), from the coast to the And... more A temporary seismic network was installed in Central Chile (30rS-32rS), from the coast to the Andes Cordillera, in order to study the seismotectonic characteristics of the flat-slab zone segment of the Nazca plate. At the zone, the subduction beneath the South America plate takes place with a convergence rate of 8 cm/yr. The local seis- micity was recorded from Nov.
E3S web of conferences, 2016
The present document describes the functioning principles of the Muon Survey Tomography based on ... more The present document describes the functioning principles of the Muon Survey Tomography based on Micromegas detectors for Unreachable Sites Technology and its distinguishing features from other Micromegas-like detectors. Additionally, it addresses the challenges found while operating the first generation and the resulting improvements. Currently, the project Temporal Tomography of the Densitometry by the Measurement of Muons is focused on obtaining a reliable pulse from the micromesh, associated to the passing of a muon, in order to trigger the acquisition and operate in standalone mode. An outlook of the future steps of the project is provided as well.
E3S web of conferences, 2016
The present document describes the functioning principles of the Muon Survey Tomography based on ... more The present document describes the functioning principles of the Muon Survey Tomography based on Micromegas detectors for Unreachable Sites Technology and its distinguishing features from other Micromegas-like detectors. Additionally, it addresses the challenges found while operating the first generation and the resulting improvements. Currently, the project Temporal Tomography of the Densitometry by the Measurement of Muons is focused on obtaining a reliable pulse from the micromesh, associated to the passing of a muon, in order to trigger the acquisition and operate in standalone mode. An outlook of the future steps of the project is provided as well.
HAL (Le Centre pour la Communication Scientifique Directe), 2002
Cahier technique AFPS-CFGI "Géologie et risque sismique", 49-5
AGU Fall Meeting Abstracts, Dec 1, 2013
HAL (Le Centre pour la Communication Scientifique Directe), 2002
Cahier technique AFPS-CFGI "Géologie et risque sismique", 49-5
HAL (Le Centre pour la Communication Scientifique Directe), Apr 7, 2019
In many areas with high telluric hazard (earthquakes, tsunamis, landslides etc.), our understandi... more In many areas with high telluric hazard (earthquakes, tsunamis, landslides etc.), our understanding of seismogenic and mechanical processes and our ability to properly asses the related hazard is still very limited by the difficulty or the impossibility to deploy arrays of high performance seismometers in areas with harsh and challenging environment (far offshore, hot/deep boreholes, mountainous regions, etc.), due to the high installations and maintaining costs, and to the risk of loss (lightning, eruptions, rock falls, power failure, etc.) or even to the absence of suitable commercial technology (high temperature). These last few years, innovative, high-resolution, low-cost optical seismometers have been developed to provide a real-time monitoring solution for regions of interest. The application fields of these significant advances are multiple: natural areas with a high telluric hazard, geo-industries (oil and gas production, geothermy, gas or waste storage), monitoring of structures, etc. The IPGP, the ESEO Group and their partners Geosciences Montpellier and the Laboratory of Analysis and Architecture Systems (LAAS) of Toulouse developed an on-land and offshore, high resolution, low-cost optical (laser) seismometer (french ANR LINES). Campaigns have been conducted in order to test and qualify their first prototype of 2 Hz - optical seismometers, at the Low Noise Underground Laboratory (LSBB) of Rustrel (France). This allowed a first validation of all opto-mechanical functions of the involved sensors, including the dedicated signal processing. Thus, the acceleration floor noise level of the sensor is lower than 1ng.Hzˆ-1/2 in the 0.3-5Hz range and remains under 10ng.Hzˆ-1/2 in the 0.15-20Hz range. One of the current fields of investigation, co-financed by the Technology Transfer Accelerator Office (SATT) Ouest Valorisation, consists in adapting these technologies to the design of a 3 components remote underwater seismometer. In this campaign, the integration of optical components, electronics for analog signal conditioning and digital signal processing has significantly improved the sensor performances and allowed an important reduction of power consumption (by a factor of ten). This autonomous device has been deployed during the past 6 months directly on a platform in the Brest harbour, collaborating with IFREMER and the Sea Test Base of ISEN. Our optical geophones were packaged in a hyperbaric chamber, buried in the seafloor, 500 meters away from the platform and at a depth of about 10 meters. This presentation aims to show the results and observations collected during these campaigns, and discuss about the short and long term perspectives.
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Papers by Stéphane Gaffet