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Savvaidis, Alexandros
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- PublicationOpen AccessAnalysis of non-double-couple source mechanisms in an area of induced seismicity, West Texas (USA)In the scope to investigate the possible interactions between injected fluids, subsurface geology, stress field and triggering earthquakes, we investigate seismic source parameters related to the seismicity in West Texas (USA). The analysis of seismic moment tensor is an excellent tool to understand earthquake source process kinematics; moreover, changes in the fluid volume during faulting leads to existence of non-double-couple (NDC) components (Frohlich, 1994; Julian et al., 1998; Miller et al., 1998). The NDC percentage in the source constitutes the sum of absolute ISO and CLVD components so that %NDC= % ISO + %CLVD and %ISO+%CLVD+%DC=100%. It is currently known that the presence of NDC implies more complex sources (mixed shear-tensile earthquakes) correlated to fluid injections, geothermal systems and volcano-seismology where induced and triggered seismicity is observed. With this hypothesis, we analyze the micro-earthquakes (M <2 .7) recorded by the Texas Seismological Network (TexNet) and a temporary network constituted by 40 seismic stations (equipped by either broadband or 3 component geophones). Our study area is characterized by Northwest-Southeast faults that follow the local stress/field (SHmax) and the geological characteristic of the shallow basin structure of the study area. After a selection based on signal-to-noise ratio, we filter (1-50 Hz) the seismograms and estimate P-wave pulse polarities and the first P-wave ground displacement pulse in time domain. Then, we perform the full moment tensor analysis by using hybridMT technique (Andersen, 2001; Kwiatek et al., 2016) with a detailed 1D velocity model. The key parameter is the polarity/area of the first P-wave ground displacement pulse in time domain. Uncertainties of estimated moment tensors are expressed by normalized root-mean-square (RMS errors) between theoretical and estimated amplitudes (Vavricuk et al., 2014). We also evaluate the quality of the seismic moment tensors by bootstrap and resampling. In our preliminary results we obtain NDC percentage (in terms of %ISO and %CLVD components), Mw, seismic moment, P, T and B axes orientation for each source inverted.
36 15 - PublicationRestrictedGeopsy: A User-Friendly Open-Source Tool Set for Ambient Vibration Processing(2020)
; ; ; ; ; ; ; ; ; ; ; ; ; Ambient vibrations are nowadays considerably used worldwide for numerous types of engineering applications and scientific research. Geopsy and its companion tools are part of that landscape. Since the first release of the program package in 2005, as outcome of the European Union project Site Effects aSsessment from AMbient noisE, Geopsy has become a mature multiplatform open-source package (released under GNU Public License version 3) that has already been recognized as a reference tool for analyzing ambient vibration data in the context of site characterization studies. The community of users has grown from a core group of researchers up to thousands of seismologists and engineers on every career level and on all continents. The versatility of geopsy allows for the processing of all kinds of data needed in site characterization studies, that is, from single station single trace to three-component array recordings. In all of the aforementioned cases, the steps from field acquisition to the production of publication-ready figures are covered and supported by user-friendly graphical user interfaces or corresponding command-line tools for the automation of the complete processing chain. To avoid black-box usage, a number of lower-level tools guarantee maximum flexibility in accessing and controlling processing results at any stage of the analysis282 5 - PublicationOpen AccessMT-data analysis from a survey in the Mygdonia basin (N. Greece)(2002)
; ; ; ;Makris, J. P.; Department of Electronics, Technological Educational Institute of Crete, Chalepa, Chania, Crete Island, Greece ;Savvaidis, A. S.; Laboratory of Geophysics, Department of Geology, Aristotle University of Thessaloniki, Greece ;Vallianatos, F.; Department of Electronics, Technological Educational Institute of Crete, Chalepa, Chania, Crete Island, Greece; ; A magnetotelluric (MT) profile comprising eight measuring sites was conducted in the Mygdonia basin, a European Seismological Test Site. The MT-stations were deployed in a direction almost perpendicular to the major axis of the sedimentary basin to cover the area between the Lagada and Volvi lakes. The earth beneath the measuring points was considered to consist of a 2D-regional basement coupled with local, near surface, 3D-inhomogeneities. Impedance tensor decomposition analysis in conjunction with the magnetotelluric study of Mohr circles was implemented in the MT-data. From the electric field polarization diagrams and the interpretation of the Mohr circles results it is inferred that the local structure at all the sites polarizes the electric field in comparable directions ranging from N60°E to N80°E, except for the cases of the two stations located at the northern and southern borders of the basin, where the boundary conditions produce a deviation. Furthermore, the deeper structure seems to be two-dimensional. The strike-direction of the 2D-basement was found to be ~ N70°E. Although the regional geological strike in the area is NW-SE, the regional geoelectric strike is more compatible with the orientation of the faults in the area.210 200 - PublicationOpen AccessSesame Project - Deliverable D04-04 - Report of the WP04 H/V Technique : Empirical Evaluation - Homogeneous Data Set of Noise and Earthquake Recordings at Many Sites(2003-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Atakan, Kuvvet; University of Bergen, Norway ;Azzara, Riccardo Mario; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Bard, Pierre-Yves; LGIT, Grenoble, France ;Cara, Fabrizio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cultrera, Giovanna; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Dimitriu, Petros; ITSAK, Thessaloniki, Greece ;Duval, Anne-Marie; CETE, Nice, France ;Faeh, Donat; ETHZ, Zurich, Swiss ;Di Giulio, Giuseppe; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Hagshenas, Ebrahim; LGIT, Grenoble, France ;Havskov, Jens; University of Bergen, Norway ;Koller, Martin; Resonance, Geneva, Swiss ;Pagani, Marco; CNR-IDPA, Milan, Italy ;Panou, Areti; ITSAK, Thessaloniki, Greece ;Papaioannou, Christos; ITSAK, Thessaloniki, Greece ;Rovelli, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Savvaidis, Alexandros; ITSAK, Thessaloniki, Greece ;Spohler, Eva; ETHZ, Zurich, Swiss ;Tento, Alberto; CNR-IDPA, Milan, Italy ;Daminelli, Rossella; CNR-IDPA, Milan, Italy ;Marcellini, Alberto; CNR-IDPA, Milan, Italy ;Theodoulidis, Nikos; ITSAK, Thessaloniki, Greece ;Zacharopoulos, Stratos; ITSAK, Thessaloniki, Greece; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In this Report the homogeneous data set of earthquake and noise recordings at many sites that is generated under the framework of the SESAME Project (Site Effects Assessment Using Ambient Excitations, EC- RGD, Project No. EVG1-CT-2000-00026 SESAME), Task A (H/V technique), Work Package 04 (WP04– H/V Technique: Empirical Evaluation), is presented. Three main topics are included in the Report: (a) The Standard Information Sheet (SIS) structure, (b) The SESAME Ascii Format (SAF) files, and (c) The SESAME SIS-database. The SIS compiled in this sub-task and SAF format adopted for all data, constitute a homogeneous data set to be processed for further scientific results in the framework of the WP04. In addition, the SIS-database is going to facilitate data selection and management.284 441 - PublicationOpen AccessSesame Project - Deliverable D20-04 - WP04 H/V Technique : Empirical Evaluation - Comparisons of Damage Distribution in Modern Urban Areas with Results from (H/V) Spectral Ratio(2004-07)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Bordoni, Paola; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Cara, Fabrizio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cultrera, Giovanna; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Dimitriu, Petros; ITSAK, Thessaloniki, Greece ;Di Giulio, Giuseppe; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Hatzidimitriou, Panagiotis; ITSAK/AUTH-Geolab, Thessaloniki, Greece ;Lenti, Luca; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Marra, Fabrizio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Marcellini, Alberto; CNR, Milan, Italy ;Milana, Giuliano; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Oliveira, Carlos; Inst. Superior Tecnico, Lisbon, Portugal ;Pagani, Marco; CNR, Milan, Italy ;Panou, Areti; ITSAK, Thessaloniki, Greece ;Papazachos, Costas; ITSAK/AUTH-Geolab, Thessaloniki, Greece ;Rovelli, Antonio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Savvaidis, Alexandros; ITSAK, Thessaloniki, Greece ;Senos, M. Luisa; Inst. Meteorology, Lisbon, Portugal ;Tento, Alberto; CNR, Milan, Italy ;Tertulliani, Andrea; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Teves-Costa, Paula; ICTE/UL, Lisbon, Portugal ;Theodoulidis, Nikos; ITSAK, Thessaloniki, Greece; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In this Report comparisons of seismic damage distribution with the (H/V) spectral ratio results is attempted, under the framework of the SESAME Project (Site Effects Assessment Using Ambient Excitations, EC-RGD, Project No. EVG1-CT-2000-00026 SESAME), Task A (H/V technique), Work Package 04 (WP04– H/V Technique: Empirical Evaluation).239 127