Deep long period earthquakes beneath volcanoes of the French Massif Central

The recent installation of new broadband seismic stations in the French Massif Central (FMC) has resulted in the detection of a few “deep” earthquakes located near the crust-mantle boundary beneath volcanic regions. Analysis of the spectral content of the respective waveforms has shown that the spectra of these “deep” earthquakes are significantly depleted in high frequencies. Based on these observations of anomalous depth and spectral content, these earthquakes can be classified as Deep Long Period (DLP) events. This is a specific class of volcanic seismicity observed beneath many active volcanoes around the World. While the exact physical origin of this type of earthquakes is still debated, they are often considered as indicators of the presence of magma near the crust-mantle boundary. Therefore, observation of DLP earthquakes can bring new insights into understanding the state and the activity of the recent FMC volcanoes.