HR: 09:05h
AN: S51C-05 INVITED     [Abstracts]
TI: Body-Wave Attenuation Structure in Central Mexico
AU: * Chen, T
EM: tchen@gps.caltech.edu
AF: Caltech, MC 252-21, 1200 E. California Blvd., Pasadena, CA 91125, United States
AU: Clayton, R W
EM: clay@gps.caltech.edu
AF: Caltech, MC 252-21, 1200 E. California Blvd., Pasadena, CA 91125, United States
AB: Velocity spectra from moderate earthquakes are used to investigate the P-wave attenuation structure in southern Mexico. We include regional events with magnitudes in the range 4.5 < M < 5.0 recorded on the Meso American Subduction Experiment (MASE) array, which consists of 100 broadband sensors from Acapulco to Tampico. By assuming a Brune-type source, a path-averaged frequency- independent Q is obtained for each seismogram in the frequency band 0.5 Hz to 7-30 Hz, depending on the signal quality. These measurements are then inverted for spatial variations in Q. The 1-D tomography result shows a pattern of Q qualitatively similar to other subduction zones, with low attenuation crust (Q ~ 1100), and high attenuation in the mantle wedge beneath the Trans-Mexico-Volcanic-Belt (Q < 250). The 2-D inversion shows a more detailed image of Q variations. The location of the low-Q region and the variation of the Q value also provides some constraints on the geometry of the subducting slab, or with the structure provided by other methods such as receiver functions, The Q estimates will be used to estimate variations in viscosity.
DE: 7200 SEISMOLOGY
DE: 7203 Body waves
DE: 7240 Subduction zones (1207, 1219, 1240)
DE: 7270 Tomography (6982, 8180)
DE: 8162 Rheology: mantle (8033)
SC: Seismology [S]
MN: 2007 Joint Assembly