CRUSTAL THICKNESS ESTIMATION USING HIGH-FREQUENCY RAYLEIGH-WAVES

The method of nonlinear waveform-fitting was extended to include changes in the depth of the Moho. Studies performed on synthetic data at 10 degrees epicentral distance showed that it is theoretically possible to determine Moho-depth with an accuracy of less than a kilometer if the frequency range extends to 0.12 Hz. We applied this method on several broadband records from two earthquakes in Western United States to invert for crustal thickness. Waveform-fitting of Rayleigh waves for epicentral distances between 3 degrees and 10 degrees for individual paths in this region show that the average Moho-depth can be resolved to 1-2 km. It was possible to obtain good waveform fits for frequencies between 0.02-0.08 Hz. We conclude that broadband seismic data from local events allow us to determine Moho-depth independently from crustal shear-wave velocity.