HR: 15:25h
AN: S33C-08    [Abstracts]
TI: Kinematic Modeling and Complete Moment Tensor Analysis of the Anomalous, Vertical CLVD Bardarbunga, Iceland, Event
AU: Dreger, D S
EM: dreger@seismo.berkeley.edu
AF: Berkeley Seismological Laboratory, University of California at Berkeley, 215 McCone Hall, Berkeley, CA 94720 United States
AU: * Tkalcic, H
EM: tkalcic1@llnl.gov
AF: Lawrence Livermore National Laboratory, Atmospheric, Earth and Energy Sciences Department, L-206, P.O. Box 808, East Avenue 7000, Livermore, CA 94550 United States
AU: Foulger, G R
S33C-08 AF: University of Durham, Department of Earth Sciences, Durham, DH13LE United Kingdom
AU: Julian, B R
S33C-08 AF: United States Geological Survey, 345 Middlefield road, Menlo Park, CA 94025 United States
AB: Using the complete moment tensor inversion method, we investigated the September 29, 1996 volcanic event of Mw=5.6 originated beneath the Badarbunga caldera in Iceland. The corresponding moment tensor is characterized by a significant non-double-couple component (NDC) previously reported in the Harvard centroid moment tensor catalog (CMT) and confirmed by analysis of long-period and intermediate surface wave data. Statistical tests confirm that CLVD is a stable component of the moment tensor, while ISO is statistically insignificant. Using an elastic finite difference code, with a large number of equidistantly distributed point sources we simulated various rupture scenarios on the walls of a conical surface of the Bardarbunga caldera in order to compare them with the observations. Suites of seismograms for each independent run were produced at locations corresponding to the Iceland Hotspot IRIS-PASSCAL stations. We then inverted these synthetic data to investigate what portion of the original source information can be recovered by the moment tensor inversion. We were able to identify physical characteristics of a rupture scenario that produces synthetics resembling the observed data to a quite high level of detail. For example, we obtained the best results for the ruptures extending along one-half perimeter of the caldera, while one-quarter or full-length perimeter ruptures were unlikely scenarios. We found that the rupture velocity, which took place at Bardarbunga could have been a super-shear one, and we hypothesize that it could have been triggered by a compressional wave field that spread throughout the volume of the caldera.
DE: 7209 Earthquake dynamics (1242)
DE: 7280 Volcano seismology (8419)
DE: 8440 Calderas
SC: Seismology [S]
MN: Fall Meeting 2005