Seismic activity at Cadamosto seamount near Fogo Island, Cape Verdes-formation of a new ocean island?

Abstract

SUMMARY In global catalogues only a handful of earthquakes occurred at or near the Cape Verde islands. The two most recent events occurring in 1998 and 2004 were observed in the southwest of the Cape Verde archipelago away from aerial volcanic centres. Event relocation suggests that both earthquakes may occur at the Cadamosto seamount, a 3-km-tall submarine volcanic edifice to the southwest of the active volcanic islands of Fogo. Swath mapping efforts revealed numerous small volcanic cones between the volcanic island of Brava and the seamount and between Fogo and Brava. The distribution of volcanic vents may support two plumbing systems, one feeding Fogo and volcanic cones between Fogo and Brava and another system feeding Cadamosto seamount. Using ocean-bottom seismic stations of opportunity, deployed roughly a month after a mb= 4.3 earthquake occurred in 2004 August near or at the Cadamosto seamount, we were able to locate local seismic activity clustering at the seamount. We propose that these events reflect brittle rock failure due to magma redistribution in or near a central magma reservoir or more likely dyke intrusion. The observations reported here suggest that Cadamosto seamount is the seismically most active feature in the archipelago. It might be reasonable to hypothesis that ongoing activity causes the Cadamosto seamount to grow, forming a new oceanic island in the future.