The seismic crisis unfolding in the Azores: earthquakes accompanying a rarely observed submarine eruption?

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A swarm of earthquakes on the seabed west of a volcanic island in the Azores (Faial) presents an exciting opportunity to find out potentially how submarine volcanic cones form and this in turn helps us to understand the risks from submarine eruptions. The swam lies at one end of an elongated volcano (Condor Seamount) where there are small volcanic cones and ridges. We will install 4 seismometers on the seabed around the site to record further earthquakes over two months. By accurately locating those earthquakes, we will be able to determine the geometries of faults and cracks filled with lava (dykes). If there has been an eruption, the seabed will have changed shape - this will be worked out from multibeam echo-sounder data collected in a new sonar survey in the summer of 2020. The combined results will show us whether there has been an eruption and if so how that eruption related to the molten lava supplied deeper in the Earth. In addition, we will be able to reassess seismic waves that have travelled through the adjacent submarine volcano to see if those waves have unusually low velocities expected for a magma chamber. The new results from the seismometers will be used to update software used by government scientists in the Azores to work out where earthquakes occur and their magnitudes, hence their monitoring service for the local population. This will further help us work out the nature of the earthquake swarm (whether associated with subterranean movement of lava or movements on faults). Submarine volcanic eruptions are less frequent in the Atlantic compared with the Pacific Ocean, but are a risk to ships, seabed cables and to local populations where associated earthquakes and landslides cause tsunamis. Understanding this Azorean event will help characterize this broader threat, of importance to the UK given its large sea areas, including those around volcanically active Ascension and Tristan da Cunha islands.