ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4pUW3. Short-range seismoacoustic propagation on and off the beach.

LeRoy M. Dorman

Allan W. Sauter

Chris Bradley

Sean Wiggins

Javier Porras

Marine Physical Lab., SIO, UCSD, La Jolla, CA 92093-0215

Cultural seismic noise (noise caused by human activities) can be used for tracking and surveillance. During June and July 1995, a field experiment, dubbed ``Adaptive Beach Monitoring'' was conducted on both sides of the shoreline at U.S. Marine Corps Base Camp Pendleton, near Oceanside, California. Various sources were observed by seafloor seismic and acoustic sensors (four ocean-bottom seismometers), and by a 24-element seismometer array ashore. Preliminary results on the propagation of surface (and interface) waves shows that the surficial shear velocity is similar on both sides of the shoreline (nominally 250 m/s). The dispersion of the waves is, however, markedly different. The dispersion of Scholte waves observed on the OBSs was strong, with group velocity varying by a factor of 2 in the 2- to 10-Hz range. Ashore, however, Rayleigh waves in the 5- to 20-Hz frequency range showed little or no dispersion. [Work sponsored by the Office of Naval Research, Code 32.]