HR: 0800h
AN: S31B-1057    [Abstracts]
TI: Rotational Motions from Teleseismic Events - Modelling and Observations
AU: * Schuberth, B
EM: bernhard@geophysik.uni-muenchen.de
AF: Dept. for Earth and Environmental Sciences, Ludwig-Maximilians-University of Munich, Theresienstrasse 41, Munich, 80333 Germany
AU: Igel, H
EM: igel@geophysik.uni-muenchen.de
AF: Dept. for Earth and Environmental Sciences, Ludwig-Maximilians-University of Munich, Theresienstrasse 41, Munich, 80333 Germany
AU: Wassermann, J
EM: jowa@geophysik.uni-muenchen.de
AF: Dept. for Earth and Environmental Sciences, Ludwig-Maximilians-University of Munich, Theresienstrasse 41, Munich, 80333 Germany
AU: Cochard, A
EM: alain@geophysik.uni-muenchen.de
AF: Dept. for Earth and Environmental Sciences, Ludwig-Maximilians-University of Munich, Theresienstrasse 41, Munich, 80333 Germany
AU: Schreiber, U
EM: schreiber@wettzell.ifag.de
AF: Forschungseinrichtung Satellitengeod„sie, Technical University of Munich, Fundamentalstation Wettzell, Sackenriederstrasse 25, K”tzting, 93444 Germany
AB: Currently only ring lasers technology is capable of recording rotational motions resulting from earthquakes with a sensitivity and frequency band that are interesting for broadband seismology. One of those instruments is located at the Geodetic observatory in Wettzell/Germany. Here we present theoretical studies of rotational motions simulated with different Earth models and comparisons with several observations at the Wettzell ring laser. The 3-D global simulations were performed with the Spectral Element Method (Komatitsch and Tromp 2002a,b), that was modified to also allow the output of rotational seismograms. The Earth models used in these simulations range from simple radially symmetric ones, such as PREM, to more complex models including 3D velocity structures, attenuation and geometric effects like topography and bathymetry. Thus, by comparison of the theoretical rotation rates with the ring laser data we show how the results converge to the observed rotation rates when using more realistic Earth models. In a second step we compare rotation rates to the transverse component of translational acceleration both obtained from simulations with 3D velocity structures in crust and mantle. As expected from theory - under the assumption of plane wave propagation - those two signals should be in phase and scale linearly with the phase velocity. Using this relation, it is possible to determine the local phase velocity of transverse signals from collocated measurments of rotations and transverse accelerations. We compare the estimated phase velocities with those observed in a temporary seismic array installed around the ring laser.
DE: 7260 Theory and modeling
SC: Seismology [S]
MN: 2004 AGU Fall Meeting