HR: 1340h
AN: S13A-1032    [Abstracts]
TI: New Constraints on the Fault Plane Structure of the Mw=6.9 Cariaco, North Eastern Venezuela Earthquake
AU: * Sobiesiak, M
EM: polar@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Grosser, H
EM: gros@gfz-potsdam.de
AF: GFZ Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Scherbaum, F
EM: fs@geo.uni-potsdam.de
AF: University of Potsdam, Institute of Geosciences, POB 601553, Potsdam, 14415 Germany
AU: Rietbrock, A
EM: ariet@liverpool.ac.uk
AF: University of Liverpool, Institute of Earth Sciences, 4 Brownlow Street, Liverpool, L69 3GP United Kingdom
AB: On 9th of July 1997 a Mw=6.9 earthquake ruptured approximately 45 to 60 km of the El Pilar vertical strike slip fault in North Eastern Venezuela. This fault is a major feature of the Caribbean-South American plate boundary with a right-lateral character of movement. We present in our study new constraints on the rupture mechanism from the spatial distribution of b-values on the fault plane and the radiated seismic energy, both derived from the aftershock sequence recorded by the German Task Force for Earthquakes. Both methods reveal inhomogeneous structures on the fault plane. We further assume that the distinct moment releases in the source time function obtained from teleseismic data coincide with the patches of high b-values. The locations of the inhomogeneities and the concentration of aftershock radiated energy in combination with the results from a local earthquake tomography study let us propose that changes in material properties are responsible for the cause of the inhomogeneous structures which might be interpreted as asperities. The real extent of the ruptured fault plane and the direction of rupture propagation are still under discussion. We examined in addition 222 aftershock focal mechanism solutions and caculated summed moment tensors on different segments of the fault. These results support the hypothesized inhomogeneity structure and give a first hint on a bi-directional rupture propagation.
DE: 1734 Seismology
SC: Seismology [S]
MN: 2004 AGU Fall Meeting