AVCEI Submarine Volcanism
Next webinars: September 26th, UTC 08:00 and October 11th, UTC 12:00
First Webinar
On September 26th, 2023, 08:00 UTC, CoSV will host the webinar entitled “Volcanic tsunamis due to trapdoor faulting in submarine calderas: Observations and physics”. This webinar will be presented by Dr. Osamu Sandanbata, Assistant Professor, Earthquake Research Institute, The University of Tokyo, Japan.
Abstract:
Tsunamis are generated not only by large earthquakes but also by submarine volcanic activity beneath/near the ocean. I have recently shown the recurrence of atypical earthquakes and tsunamis due to intra-caldera faulting events, called trapdoor faulting, in submarine calderas. In this talk, I will provide comprehensive overview of key findings on submarine trapdoor faulting, through case studies of Sumisu Caldera (Japan), Curtis Caldera (New Zealand), and Kita-Ioto Caldera (Japan).
To register for the webinar, click this link.
Second Webinar
On October 11th, 2023, 12:00 UTC, CoSV will host the webinar entitled “Mayotte’s submarine volcanic system: seismicity distribution and insights from modeling”. This webinar will be presented by Dr. Lise Retailleau, Research Scientist, Institut de Physique du Globe de Paris, France
Abstract:
The 2018-2021 Fani Maoré eruption that occurred east of the coast of Mayotte, in the Mozambique channel, is the largest submarine eruption ever recorded. Intense seismicity occurred along with the eruption and is still active today. Using a recently-developed comprehensive automatic catalog, we explore 2 years of the volcano-tectonic, analyzing in details the active structures of the magmatic plumbing system. The seismicity is distributed in two clusters that are unexpectedly deep (25-50 km depth). The complex proximal cluster is the closest from Mayotte (10 km) and its origin is still a debate. The distal cluster is related to magma propagation towards Fani Maoré. Exploring the seismicity distribution and evolution of the two clusters, we highlight magma storage zones and aseismic conduits in the proximal cluster, as well as a regime change in the magmatic system in March 2020, giving insights into its mechanisms. To provide a first-order explanation of the processes behind the proximal cluster and its distribution, we perform finite elements modeling of pressurized magma reservoirs in an elastoplastic domain. We assess whether the proximal cluster could result from the interaction of two superimposed magma bodies. We find that two nearby reservoirs with opposite pressure signs can produce a shear fracture area matching the first-order conical shape of the seismicity distribution. We thus propose that a magma reservoir at Moho depth may have been recharged during the recent eruption. We also find that, given the large depths studied, very low strength parameters must be chosen to reach the failure threshold. This, in turn, indicates likely mantle weakening near Mayotte by preexisting fractures or pore fluids.
