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Wathelet, Marc
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Wathelet, Marc
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- 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 AccessSITE AND SEISMIC STATION CHARACTERIZATION: AN EUROPEAN INITIATIVE(2018-09)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Site characterization is a key input in seismic hazard and risk assessment (e.g. Ground Motion Prediction Equation, microzonation studies, damage scenarios) and seismic design (building codes, critical facilities). Although the number of strong-motion stations in free-field and engineering structures has largely increased over the world in the last twenty years, only a limited number of sites includes detailed site condition indicators: mostly geology and EC8 soil class, more rarely shear-wave velocity (Vs) information (e.g. Vs30 and Vs profiles), without proper documentation and quality assessment in most cases. This lack of information is a critical issue, e.g. for deriving reference rock/soil velocity profiles for region-specific GMPEs, site-specific hazard assessment, vs-kappa adjustments, seismic response of engineering infrastructures, risk modeling at urban or regional scale. Within the framework of the SERA “Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe” Horizon 2020 Project, a networking activity has been set up to propose a comprehensive European strategy and standards fostering site characterization of seismic stations in Europe. We will present the status of this networking activity that focuses on several issues. The first target is to evaluate the most relevant site characterization scalar, depth and frequencydependant indicators (e.g. Vs30, resonance period, velocity profiles, kappa, amplification factors and functions, etc.) for seismic hazard purposes and, thereafter, to propose best practice for site characterization together with standards for overall quality metrics on site characterization. The second target focuses on disseminating, within the broader seismological and engineering community, site characterization metadata developed within the EU NERA and EPOS-IP projects in order to validate and/or further develop metadata format schemes for wide use. Based on available site characterization information in Europe and considering the research and engineering needs, the third target proposes to set up a road map to prioritize strong motion site characterization in Europe for the next decade. Finally, a task is dedicated to investigate relevance of new site condition and amplification proxies (for example combining resonance frequency, local slope and other parameters, proxy for non-linear effects, wavelength-scaled curvature and topographic position index position as proxies for topographic effects, aggravation factor for basin effects, etc.) and their implementation at the European scale and into site characterization metadata.76 19 - PublicationOpen AccessAnatomy of a fumarolic system inferred from a multiphysics approach(2018-05-15)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ;; ;; ; ;Fumaroles are a common manifestation of volcanic activity that are associated with large emissions of gases into the atmosphere. These gases originate from the magma, and they can provide indirect and unique insights into magmatic processes. Therefore, they are extensively used to monitor and forecast eruptive activity. During their ascent, the magmatic gases interact with the rock and hydrothermal fluids, which modify their geochemical compositions. These interactions can complicate our understanding of the real volcanic dynamics and remain poorly considered. Here, we present the first complete imagery of a fumarolic plumbing system using three-dimensional electrical resistivity tomography and new acoustic noise localization. We delineate a gas reservoir that feeds the fumaroles through distinct channels. Based on this geometry, a thermodynamic model reveals that near-surface mixing between gas and condensed steam explains the distinct geochemical compositions of fumaroles that originate from the same source. Such modeling of fluid interactions will allow for the simulation of dynamic processes of magmatic degassing, which is crucial to the monitoring of volcanic unrest.462 79