The OVSM-IPGP recommends the passage to the level of volcanic vigilance (yellow) for la Montagne Pelée.
The Volcanological and seismological observatory of Martinique of the IPGP (Institut de physique du globe de Paris, CNRS) sent Thursday 3 December, a report to the Préfet de la Martinique to recommend the passage to the volcanic alert level of yellow for Montagne Pelée (the 2nd level of alert on a scale comprising 4 levels).
This recommendation of the OVSM-IPGP follows the detection of the evolution of seismic signals recorded in the framework of the monitoring of the volcano by the observatory and the consultation with a group of experts that have studied these phenomena.
Located to the north of the island of Martinique, Montagne Pelée, is a stratovolcano linked to the Lesser Antilles subduction zone, that has experienced at least 4 eruptions over the past 250 years: phreatic eruptions without magma input in 1792 and in 1851, and two magmatic eruptions, including the infamous eruption from 1902 to 1905 and the last one from 1929 to 1932.
- Since 1980 and the existence of modern monitoring networks, the volcanic seismicity under Mount Pelée has been typically very low, a few dozen earthquakes per year on average are recorded. Earthquake swarms have already been clearly recorded in 1980, 1985-1986, 2007 and 2014. However, the swarms of 2007 and 2014 could be directly linked to high magnitude tectonic earthquakes in the Lesser Antilles region. The increase in seismicity of superficial volcanic origin (up to 4-5 km below the summit) observed since April 2019, is therefore clearly above the baseline level for Mount Pelée. Although this seismicity may be linked to the gradual increase of tectonic seismicity on a regional scale (subject of ongoing research) which could perturb the stress field of the volcano, it is clearly not associated with major tectonic earthquakes such as in 2007 and 2014. This increase could therefore also result from modifications in the activity of the hydrothermal system under Mount Pelée.
- In addition, in April 2019, we recorded deeper volcanic seismicity in the vicinity and below Mount Pelée (more than 10 km below sea level). This could correspond to the arrival at depth of magmatic fluids.
- Finally, we recorded new tremor-type signals on November 8 and 9, 2020. They could correspond to the reactivation of the hydrothermal system. Research is underway to better determine the processes behind these signals and in particular a possible influence of heavy rainfall during this period.
Even if, in the current state of the measurements, there is no deformation of the volcano on the scale of the monitoring network, the appearance, over a few months, of these three different types of seismic signals of volcanic origin shows a clear change in the behavior of the volcanic system. Indeed, its activity has increased above the base level as observed over several decades.
As a result, the OVSM-IPGP, after discussion with a group of around 20 experts from the institute, is increasing its vigilance and recommending a change to the yellow alert level.
This change to the yellow volcanic alert level corresponds to a reinforcement of the monitoring resources deployed by the OSVM and the mobilization of additional resources (human and instrumental resources) at IPGP in order to better monitor and analyze the situation in real time as well as track the behaviour and evolution of the volcanic system.
The Martinique prefecture has followed this recommendation and the Montagne Pelée area goes to the yellow volcanic alert level as of December 4, 2020.
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