The quest for the source area of the 1755 Lisbon erthquake - revealing the maximum depth of seismogenic faulting in the Horseshoe abyssal plain

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The Gulf of Cadiz and the Horseshoe abyssal plain are characterized by diffuse seismic and tectonic activity and the region lacks a clear plate boundary separating Africa from Eurasia/Iberia. The area hosted with the Great Lisbon earthquake of 1755 the largest European earthquake since historic earthquakes were reported. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work, however, suggested that the event occurred in the vicinity of the Horseshoe fault, an oblique thrust fault. The Horseshoe fault is cut by prominent features in the bathymetry – the SWIM lineaments. The SWIM lineaments are believed to facilitate fluid migration. The work proposed here has two main aims: (i) surveying the seismogenic potential of the area by yielding the maximum depth of seismogenic faulting and (ii) relating fluid seepage to seismically active faults. Therefore, as a piggy back project to the RV Meteor cruise M86/1 a small network of OBS shall be deployed in the Horseshoe abyssal plain and across the Horseshoe fault, recording earthquakes over 5-7 month.