HR: 16:35h
AN: S44B-03 INVITED    [Abstracts]
TI: Exploring the Seismic Wavefield with EarthScope's Transportable Array
AU: Ammon, C J
EM: cammon@geosc.psu.edu
AF: Department of Geosciences, Penn State, University Park, PA 16802, United States
AU: * Lay, T
EM: thorne@pmc.ucsc.edu
AF: Earth and Planetary Sciences Department, University of California, Santa Cruz, CA 95064,
AB: The unprecedented aperture and dense station spacing of EarthScope's Transportable Array (TA) provide opportunities to explore subtle features of the seismic wave field using array methods, including stacking to enhance signals from small, distant events, and using spatial animations and slowness spectra to investigate the origin and nature of long-period (tens to hundreds of seconds) seismic coda. We illustrate the TA's capabilities using teleseismic short-period P waves and complete broadband ground motion recordings. The high quality and uniform installation procedures of the TA produce many stations with superb short-period signal- to-noise ratios enabling direct detection of tiny amplitude (~2nm) P-waves from the mb 4.2, 09 October, 2006 North Korean nuclear test. Stacking of many TA signals resolves subtle complexity in the source signals. Guided by seismic wavefield animations from large earthquakes, which display many wavefronts sweeping across the array, visual inspection and seismic slowness spectra of the extended coda resolve off-great circle Rayleigh-wave arrivals. The scattered waves approach the array from preferred directions depending on the source location relative to the TA. For example, scattered signals from the 01 April, 2007 Solomon Islands earthquakes are preferentially located to the west and northwest, with timing that suggests scattering from subduction zones along the margin of the western and north Pacific ocean. For the 16 August, 2007 Central Peru earthquake, Rayleigh wave coda contains significant energy arriving from the north and northeast, scattered near the North American margin. Analysis of scattered arrivals may lead to improved constraints on lateral gradients in lithospheric structures.
DE: 1236 Rheology of the lithosphere and mantle (7218, 8160)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 7200 SEISMOLOGY
DE: 7255 Surface waves and free oscillations
DE: 7294 Seismic instruments and networks (0935, 3025)
SC: Seismology [S]
MN: 2007 Fall Meeting