PRELIMINARY WORK ON AN EARLY WARNING AND RAPID RESPONSE PROGRAM FOR MODERATE EARTHQUAKES

Warning of imminent ground shaking due to a large earthquake would be useful to a variety of agencies. This kind of ground-motion prediction is possible in southern California for events with magnitude less tha n 6, where path effects dominate, The 28 June 1991 Sierra Madre earthq uake is presented as a test case for this concept. A single-station in version of the record from the Pasadena station 20 km SW of the epicen ter produces reasonable source parameters for the event. With these so urce parameters and a library of Green's functions calculated for an a verage southern California crustal model, ground motions can be predic ted throughout the region. In particular, since the peak displacement for the Sierra Madre event occurs at Pasadena before ground motion beg ins at a station near the San Andreas Fault in San Bernardino, ground motions near the San Andreas Fault can be calculated before the seismi c energy has propagated into the area. Considering this scenario in th e reverse direction, records from a station near an earthquake on the San Andreas Fault could be used to predict ground motions in the metro politan Los Angeles area. Broadband, high-dynamic-range seismic instru ments produce high-quality records for events over a wide magnitude ra nge. Thus, the development of a warning system can be approached in st ages, starting with small events, With path effects determined by mode ling moderate-size events, work can begin on developing distributed fa ult models to predict ground motions of great earthquakes.