Source Studies in the Near- and Far-Field

Examination of the seismic source from both the near- and farfields has been undertaken. Using a discrete Fourier transform (DFT) and a maximum entropy spectral estimator on near-field acceleration data produced corner frequency and low frequency level estimates. This latter estimator eliminates leakage, thereby obtaining more accurate values for the high frequency end, with better roll-off values and definition of side lobes. When the maximum entropy spectral estimator was applied to data from the Parkfield earthquake and the Bear Valley event of June 22, 1973, the lower frequency level was lower than that from the DFT in all cases. Using spectral fitting procedures on fundamental mode surface wave data from two central California events, generally close agreement was obtained with source mechanism solutions from bodywaves. For the Bear Valley earthquake of June 22, 1973, the seismic moment obtained from the surface wave data was an order of magnitude smaller than that obtained from acceleration data.
See also ADA005786.