HR: 0800h
AN: V21A-0594    [Abstracts]
TI: Profiling Lithospheric Strength: Determining the Depth Extent of Seismicity in the Zagros Mountains Using Moment Tensor Inversion of Regional Earthquakes
AU: * Adams, A N
EM: aadams@geosc.psu.edu
AF: Department of Geosciences, Pennsylvania State University, 503 Deike Building, University Park, PA 16802 United States
AU: Nyblade, A
EM: andy@geosc.psu.edu
AF: Department of Geosciences, Pennsylvania State University, 503 Deike Building, University Park, PA 16802 United States
AU: Brazier, R
EM: rab27@psu.edu
AF: Department of Geosciences, Pennsylvania State University, 503 Deike Building, University Park, PA 16802 United States
AU: Rodgers, A
EM: rodgers7@llnl.gov
AF: Lawrence Livermoore National Laboratory, 7000 East Avenue, Livermore, CA 94550 United States
AU: Al-Amri, A
EM: amri444@yahoo.com
AF: King Saud University, Geophysical Observatory, Riyadh, 11451 Saudi Arabia
AB: A recent debate has called into question previous assumptions regarding continental lithospheric structure. The Zagros Mountains of southwestern Iran have been cited in the past as an example of the "jelly sandwich" lithosphere - a lithosphere consisting of a strong upper crust and strong uppermost mantle separated by a weak lower crust. Historical records of earthquake depths within this region have indicated the presence of upper mantle seismicity beneath the Zagros Mountains, supporting the theory of the jelly sandwich lithospheric structure. Recent recalculations of earthquake depths using teleseismic data, however, have challenged this theory, finding no evidence of upper mantle earthquake focal depths. This study aims to address this debate by using moment tensor inversion of earthquakes occurring within the Zagros Mountains region that are recorded at regional distances. Stations for this study come from several permanent and temporary regional networks consisting of broadband, long-period, and short-period seismometers. The majority of the data is from the Saudi Arabian National Digital Seismic Network (SANDSN), whose stations are located primarily within the Arabian Shield. These SANDSN stations include 11 short-period and 27 broadband three-component seismometers. Focal mechanisms and focal depths calculated using regional data will be presented for earthquakes in the Zagros Mountains with mb > 4. This will establish a more complete and accurate record of focal mechanisms and focal depths than is currently available from the Harvard CMT catalog, providing better resolution of the depth extent of seismicity within the Zagros Mountains. With improved records of the extent of seismicity, we will be better able to determine whether the strength of the upper mantle beneath the Zagros Mountains supports the theory of a jelly sandwich lithospheric structure.
DE: 7205 Continental crust (1219)
DE: 7218 Lithosphere (1236)
DE: 8108 Continental tectonics: compressional
DE: 8123 Dynamics: seismotectonics
DE: 8159 Rheology: crust and lithosphere (8031)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005