IASPEI - Picture Gallery

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS002 Poster presentation 1791
Tsunami deposits in the western Mediterranean: the remains of the 1522
Almera earthquake
Prof. Klaus Reicherter
Neotectonics and Natural Hazards RWTH Aachen University
Peter Becker-Heidmann
The 1522 Almera earthquake (M > 6.5) affected large areas in the western Mediterranean and caused
more than 2000 causalities. Different epicentral areas have been suspected, mainly along the 50 km
long sinistral Carboneras Fault Zone (CFZ), however no on-shore surface ruptures and
paleoseismological evidences for this event have been found. High-resolution sea floor imaging (narrow
beam sediment profiler) yields evidence for an offshore rupture along a strand of the CFZ that is
supported by evaluation of historic documents. Based on these data, a new epicentral area precisely at
the observed sea floor rupture area is proposed at N 36 42, W 2 23 in the Gulf of Almera. Drilling in
lagunas and salinas of the Cabo de Gata area proved sedimentary evidence for paleo-tsunamis along
the Spanish Mediterranean coast. Several coarse grained intervals with fining-up and thinning-up
sequences, rip-off clasts, broken shells of lamellibranchs and foraminifera show erosive bases. The
coarse-grained intervals show up to three sequences divided from the next one by a small clayey layer.
These intervals are interpreted as a tsunami trail and correspond to three individual waves. We have
also found multiple intercalations of those tsunamites downhole, which is interpreted as either an
expression of repeated earthquake activity or tsunami-like waves induced by submarine slides triggered
seismic shaking in the Gulf of Almera. The coast of southern Spain, the Costa de Sol, is one of the
touristic hot spots in the Mediterranean Europe and very densely populated. Hence, the impact on the
vulnerability is of great concern for society and economy, considering destructive earthquakes in costal
residential and industrial areas, especially a holiday and recreation area in the western Mediterranean
region. Our evidence suggests a certain tsunami potential and hazard for offshore active and
seismogenic faults in the western Mediterranean region.
Keywords: tsunamites, tsunami deposits, western mediterranean