Source Process of the Very Low Frequency Earthquakes During the Mayotte 2018-2019 Seismo-Volcanic Crisis
Abstract
The seismo-volcanic crisis that started in May 2018 east of Mayotte (Comoros archipelago) has been accompanied by several very low frequency earthquakes (VLF), similar to the one recorded by the global seismograph network on 11 November 2018. These events are characterized by a quasi-monochromatic waveform with dominant period of ~15 s and exponential decay over a long duration (~2000 s), and by Rayleigh-wave like polarization.
While these signals can be modelled through a damped oscillator (e.g., Lemoine et al., 2019), the physical processes at their origin (e.g., magmatic fluid oscillating within a reservoir) and their relationship with the volcano-tectonic system offshore Mayotte is unclear. Here we report on more than 200 VLFs between May 2018 and July 2019 using regional stations in Madagascar and East Africa and local stations in Mayotte, as well as ocean bottom hydrophones from the MAYOBS campaign (Feuillet et al., 2019). The events are detected using two approaches, which are discussed and compared: STA/LTA triggering on band-pass filtered traces, followed by a post-processing step; pattern recognition on spectrograms. Event location is performed though spatial 3D back-projection of station-pair cross-correlation functions (Poiata et al., 2016), assuming surface-wave speed. The retrieved epicentral locations are confirmed by amplitude ratios at station pairs. To better constrain event depths and to characterize the source mechanism, we model the moment tensor for the main events combining seismic waveforms and GNSS data from 6 stations in Mayotte, Grande Glorieuse and Madagascar. The results are discussed in light of a mechanical model of a resonating conduit and in relation with the seismic activity and the year-long deformation process characterizing the Mayotte seismo-volcanic crisis, as measured by GPS and quantified through elastic modeling.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.V43I0222S
- Keywords:
-
- 8499 General or miscellaneous;
- VOLCANOLOGY