Carola Leva, Georg Rümpker, Frederik Link, Ingo Wölbern

Fogo volcano belongs to the Cape Verde hotspot and its most recent eruption occurred from November 2014 to February 2015. From January to December 2016 we operated a temporary seismic network on Fogo and were able to locate 289 earthquakes in total. While most of the events occur at distances > 25 km near the neighboring island of Brava. However, on 15th August 2016 we recorded an isolated cluster of more than 20 earthquakes, 13 of which could be located beneath the southern part of Fogo. Differences between S- and P-wave arrival times at steep incidence clearly indicate focal depths between approximately 38 and 44 km, whereas the Moho discontinuity has been reported at about 14 km depth. This indicates that the earthquakes occur well within the upper mantle directly beneath Fogo. The observations suggest that the high strain rates required for the deep events result from fracturing induced by magma injection. The results further indicate that the magmatic source region of previous eruptions is indeed located at greater depth beneath Fogo and not Brava as previously hypothesized.