Full-Waveform Inversion of a 3D Marine-Land Dataset at Santorini Volcano
Abstract
Santorini volcano (Greece) has a long record of disastrous, caldera-forming eruptions. Its recent (2011-2012) uplift indicates an emplacement of a magmatic intrusion at 4 km beneath the Earth's surface. The melt-rich zone is believed to be a part of a multi-level plumbing system rooted in the lower crust. Constraining its geometry and physical properties would provide a key framework for hazard assessment and petrological studies of the continental crust. In order to image the volcanic system in unprecedented detail we collected a 3D wide-angle, multi-azimuth seismic dataset using 154 seismic stations (89 ocean-bottom seismometers, 65 land stations) and over 13,000 marine sound sources. First, we performed a tomographic inversion of over 140,000 first-arrival times of Pg phases refracted within the crust. A resulting P-wave velocity model served as a starting point of a subsequent full-waveform inversion (FWI) relaxing resolution-limitations of the travel-times method. We applied a 3D acoustic, time-domain full-waveform inversion using a finite-difference (FD) scheme defined on a regular grid. To retain a high-order accuracy of the forward simulation, we implemented an improved immersed boundary method capable of handling irregular model boundaries such as the steep topography of the Santorini caldera.
The obtained P-wave velocity model reveals the geometry of the magmatic plumbing system down to about 5 km depth. Two low-velocity zones can be distinguished at 0-2 km and >4 km depth respectively. The shallow one corresponds to porous caldera collapse breccia saturated with high temperature hydrothermal fluids and gases. The deeper one can be associated with the melt-rich zone and matches the position of the pressure source of the 2011-2012 uplift inferred from geodetic data. The model also provides constraints on the tectonic structures associated with the caldera, offering new insight into magma tectonic interaction and the dynamics of caldera collapse.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.S52A..07C
- Keywords:
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- 7260 Theory;
- SEISMOLOGYDE: 7270 Tomography;
- SEISMOLOGYDE: 7290 Computational seismology;
- SEISMOLOGY