Using submarine lava explosion signals to track a recent active vent evolution in Mayotte volcanic zone

Abstract:

Submarine volcanic activity is often associated with acoustic signals that can be recorded at large distances. In October and November 2019, explosive signals were recorded by an Ocean Bottom Seismometer (OBS) array that was deployed as part of the ongoing monitoring effort of the Mayotte seismo-volcanic crisis (https://doi.org/10.18142/291).

Seen on almost all 16 OBS, these acoustic signals can be associated with a recently formed sea-bottom feature first identified during the Mayobs-5 cruise in August 2019 and confirmed during the Mayobs-13-2 cruise in May 2020.

The MAYOBS/REVOSIMA seismology group manually screened the continuous data from the deployment and identified more than 400 of these signals. At first glance, the events do not occur at a steady continuous rate. This suggests different phases of the eruption during the October-November period.

We were able to identify the different reflections in the water column from the signal and to model the acoustic wave propagations with the CAKE python library. We then back-propagated the different reflections to locate the explosion sources in the vicinity of a 300m high seamount that was formed between August 2019 and May 2020.

The signals recorded by the closest OBS, located at a few hundred meters from the seamount then helped constrain the elevation of the explosion sources and reconstruct the development of the new seamount.