2aUW3. T-wave source level and earthquake fault parameters: Empirically derived scaling relationships.

Session: Tuesday Morning, December 3

Time: 8:35

Author: Robert P. Dziak
Location: CIMRS/NOAA, OSU Marine Sci. Ctr., Newport, OR 97365
Author: Christopher G. Fox
Location: Marine Sci. Ctr., Newport, OR 97365
Author: Philip D. Slack
Location: Woods Hole Oceanograph. Inst., Woods Hole, MA 02543-1541


Since 1991, NOAA/PMEL has routinely detected Tertiary waves from NE Pacific ocean earthquakes using the U.S. Navy's SOSUS hydrophone arrays. Tertiary (T) waves are seismically generated acoustic waves (between 5--50 Hz) that propagate over great distances in the oceanic sound channel with little loss in signal strength. Low attenuation, combined with the availability of detailed ocean acoustic velocity models, have made T waves extremely useful for monitoring seafloor earthquakes; T waves allow for highly accurate epicentral locations, and a reduction of the detection threshold by almost two orders of magnitude. However, it is still not well understood how seismic energy generated at the earthquake source propagates through the seafloor--ocean interface and couples to the sound channel. Hence, the relationship between earthquake source parameters and the T-wave amplitude recorded at the hydrophone are not directly known. The goal of this paper is to empirically compare earthquake magnitude, seismic moment, and fault orientation (radiation pattern) to an event's T-wave source level to see if systematic relationships exist. T-wave source level is estimated by deconvolving instrument gain and the transmission loss from the T-wave signal, thus resulting in the earthquake's acoustic energy at the seafloor--ocean interface.

ASA 132nd meeting - Hawaii, December 1996