High frequency seismic signal generated by landslides on complex topographies: from numerical simulation to field observation at Dolomieu crater, La Réunion
Abstract
Mass wasting processes such as landslides are common phenomena in volcanic environments as for example at Dolomieu crater on Piton de la Fournaise (La Réunion) since its caldera collapse in 2007. During their downslope movement along the topography, landslides generate seismic waves in a wide frequency range. The recorded signals are used to deduce landslide properties and dynamics. For example, the landslide volume can be calculated from the recorded high frequency seismic energy (Hilbert et al., 2011; typical dominant frequency range for Dolomieu crater rockfalls: 1-20 Hz). In order to get reliable results, the energy is calculated by averaging the seismic signals recorded at different seismic stations. However, topography and other path effects may significantly change the amplitudes at different stations, especially at high frequencies. We address this issue here by simulating seismic wave propagation including a detailed description of the (distributed) landslide seismic source and the complex natural topography. The time dependent spatial distribution of the forces applied to the ground by the landslide are obtained using granular flow numerical modeling on 3D topography. The generated seismic waves are simulated using the spectral element method. Finally, the simulated seismic signals are compared to observed seismic data from rockfalls at Dolomieu crater. We show that topography explains a significant part of the observed strong differences of amplitudes at different stations. We quantify topography effects by means of numerical modeling and suggest to take them into account for each station separately in order to calculate the rockfall volume from the recorded seismic signals. Hibert et al. (2011). Slope instabilities in Dolomieu crater, Réunion Island: From seismic signals to rockfall characteristics. Journal of Geophysical Research: Earth Surface, 116(4):1-18.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V11C..04K
- Keywords:
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- 7280 Volcano seismology;
- SEISMOLOGYDE: 8414 Eruption mechanisms and flow emplacement;
- VOLCANOLOGYDE: 8419 Volcano monitoring;
- VOLCANOLOGYDE: 8434 Magma migration and fragmentation;
- VOLCANOLOGY