HR: 0800h
AN: S51B-0507    [Abstracts]
TI: Estimating source parameters and uncertainties using a small aperture array
AU: * Kane, D L
EM: dlkane@ucsd.edu
AF: Scripps Institution of Oceanography, UC San Diego, IGPP/SIO 9500 Gilman Dr. #0225, La Jolla, CA 92093-0225, United States
AU: Prieto, G A
EM: gprieto@stanford.edu
AF: Stanford University, Department of Geophysics 397 Panama Mall, Stanford, CA 94305-2215, United States
AU: Vernon, F L
EM: flvernon@ucsd.edu
AF: Scripps Institution of Oceanography, UC San Diego, IGPP/SIO 9500 Gilman Dr. #0225, La Jolla, CA 92093-0225, United States
AU: Shearer, P M
EM: pshearer@ucsd.edu
AF: Scripps Institution of Oceanography, UC San Diego, IGPP/SIO 9500 Gilman Dr. #0225, La Jolla, CA 92093-0225, United States
AB: Source parameter estimation is crucial for studying the physics of earthquake rupture. Several past studies have estimated source parameters but have neglected to calculate the uncertainties of these measurements. We use waveforms of co-located earthquakes recorded at closely spaced surface stations to quantify variations in similar waveforms. Our data are from a small aperture array at Pinon Flats Observatory, California, that recorded ~150 local earthquakes (M0.7 to M3.7) over a one month period. The array consisted of 58 high frequency surface stations; 36 stations were placed in a square grid with 7m spacing and 22 stations were in two orthogonal linear arrays with 21m spacing. Two borehole stations were centered in the grid at depths of 150m and 300m. For each local earthquake, we calculate source parameters in both the frequency and time domains. Empirical Green's function (EGF) techniques are used to remove path effects while leaving local site effects intact. The close spacing and identical instrumentation of the seismic stations results in very similar records at each station and allows us to perform computations on a group of records rather than on each record individually. In the frequency domain, we compute the multitaper spectrum for each earthquake pair (main earthquake and EGF earthquake) at all stations and fit an w-2 source spectrum model over all records simultaneously to determine seismic moment and corner frequency. Similarly, we compute source-time functions in the time domain. We determine uncertainties in the source parameters by using jackknife resampling techniques. Though the individual seismic records for any given earthquake show little variation among stations, we find that the measured source parameters display scatter that cannot be neglected.
DE: 7215 Earthquake source observations (1240)
SC: Seismology [S]
MN: 2007 Fall Meeting