HR: 0800h
AN: S51D-1040    [Abstracts]
TI: First evidence for an earthquake-induced tsunami and tsunamites in the western Mediterranean: the 1522 Almera earthquake
AU: Betzler, C
EM: betzler@geowiss.uni-hamburg.de
AF: Geologisch-Palaeontologisches Institut, Universitaet Hamburg, Bundesstrasse 55, Hamburg, HH 20146 Germany
AU: * Reicherter, K
EM: reicherter@dkrz.de
AF: 1Institut fuer Geophysik und Geologie, Universitaet Leipzig, Talstrasse 35, Leipzig, 04103 Germany
AU: Huebscher, C P
EM: huebscher@dkrz.de
AF: Institut fuer Geophysik, Universitaet Hamburg, Bundesstrasse 55, Hamburg, HH 20146 Germany
AU: Becker-Heidmann, P
EM:
AF: Institut fuer Bodenkunde, Universitaet Hamburg, Bundesstrasse 55, Hamburg, HH 20146 Germany
AB: The 1522 Almeri-a earthquake (M > 6.5) affected large areas in the western Mediterranean and caused more than 2500 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. We present a new isoseist map of the 1522 Almeri-a earthquake. 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 Almeri-a. Drilling in lagunas and salinas of the near-by 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, 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 tsunamites. We have also found multiple intercalations of those coarse grained layers 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 Almeri-a. 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.
DE: 1219 Gravity anomalies and Earth structure (0920, 7205, 7240)
DE: 7250 Transform faults
DE: 8036 Paleoseismology (7221)
SC: Seismology [S]
MN: Fall Meeting 2005