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Woith, H.
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- PublicationRestrictedIntegrated tomographic methods for seismic imaging and monitoring of volcanic caldera structures and geothermal areas(2018)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ; ; ;In this paper we present innovative methodologies for seismic monitoring of volcanic structures in space and time (4D) which can possibly evolve toward an unrest stage. They are based on repeated phase and amplitude measurements done on active and/or passive seismic data including shots, vibrations, earthquakes and ambient noise in order to characterize the structure of the volcano and track its evolution through time. The characterization of the medium properties is performed through the reconstruction of an image of the elastic and anelastic properties of the propagation mediumcrossed by seismicwaves. This study focuses on the application of specific tomographic inversion methods to obtain high quality tomographic images. The resolution of the tomographic models is influenced by the number and spatial distribution of data. The expected resolution thus guides the setup of, for example, active seismic surveys. To recognize andmonitor changes in the properties of the propagation medium without performing an active survey we identify a fast proxy based on the time evolution of the Vp/Vs ratio. The advantages and limitations of the methods are discussed through synthetic tests, resolution analysis and case studies in volcanic areas such as the Campi Flegrei (southern Italy) and The Geysers geothermal area (California).110 7 - PublicationRestrictedInvestigating the Origin of Seismic Swarms(2013-10-08)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Govoni, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Passarelli, L.; GFZ, Physics of Earthquakes and Volcanoes Section ;Braun, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Maccaferri, F.; GFZ, Physics of Earthquakes and Volcanoes Section ;Moretti, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Lucente, F. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Rivalta, E.; GFZ, Physics of Earthquakes and Volcanoes Section ;Cesca, S.; University of Potsdam, Institute of Earth and Environmental Science ;Hainzl, S.; GFZ, Physics of Earthquakes and Volcanoes Section ;Woith, H.; GFZ, Physics of Earthquakes and Volcanoes Section ;De Gori, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Dahm, T.; GFZ, Physics of Earthquakes and Volcanoes Section ;Chiarabba, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Margheriti, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; ; ; ; ; ; ;; ; ; ; ; ; According to the U.S. Geological Survey’s Earthquake Hazards Program, a seismic swarm is “a localized surge of earth- quakes, with no one shock being conspicuously larger than all other shocks of the swarm. They might occur in a variety of geologic environments and are not known to be indicative of any change in the long- term seismic risk of the region in which they occur” (http://vulcan.wr.usgs.gov/Glossary/ Seismicitydescription_earthquakes.html). The definition reveals how little is actually known about seismic swarms. For example, could certain seismic settings be more prone to swarms? Could a fault zone prone to large energetic earthquakes release part of its stress through seismic swarms? Do swarms keep hazards in balance, or could their onset increase hazards? To gain insight into the nature of seismic swarms in nonvolcanic areas and to better understand their influence on seismic hazards, the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the German Research Centre for Geoscience (GFZ) began a combined research project within the framework of the Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation (NERA; see http:// www.nera-eu.org/). The project focused on monitoring swarm activity occurring in the Pollino range in Southern Apennines, Italy.737 44