A preliminary note was written by Lee on the night of Sept. 20, based on the information received in e-mails from the CWB AutoLocation system. This is the first report based on some seismic waveform data and preliminary results that Lee had received. More specific reports containing tables, graphs, and maps will be prepared later today.
Very good estimate of the hypocenter and magnitude was determined automatically in about 100 seconds (after the earthquake's origin time), and I received this information in an e-mail, several minutes later. Thousands of aftershocks have been recorded.
This program was executed by the CWB's Seismology Center under the direction of Dr. T. C. Shin (now Deputy Director-General of CWB). An advisory committee consists of about 10 seismologists and earthquake engineers assisted CWB in the planning of the program and the design of the instrumentation. Cooperative projects with the U. S. Geological Survey (1991-1995), and with the Southern California Earthquake Center (1991-present) greatly accelerated the implementation and successful operation.
Taiwan is a small island, about 8% of the area of California or Japan. With the above instrumentation, Taiwan operates the densest digital strong-motion instruments of the world. For comparison, station spacing of the free-field accelerographs in Taiwan is about 3 km in the metropolitan area (vs a 25-km uniform spacing of K-Net in Japan). The basic design of the realtime strong-motion array system for structures has since been implemented by PG&E for the headquarter building in San Francisco, and is now being implemented in the Millikan Library building of Caltech and in a building at UCLA.
CWB's Rapid Earthquake Information Release System (AutoLocation) began operation in March 5, 1996. Continuously telemetered data from 60+ digital accelerographs were automatically processed in a dual PC-based system (for redundancy) in Taipei, using hardware and software designed and implemented in the early 1990's (Lee et al., 1996; Shin et al., 1996). Early results had been published by Teng et al. (1997), and by Wu et al. (1997).
Shin TC, Tsai YB, and Wu YM (1996). Rapid response of large earthquake in Taiwan using a realtime telemetered network of digital accelerographs. Proc. 11th World Conf. Earthq. Eng., Paper No. 2137.
Teng TL, Wu L, Shin TC, Tsai YB, and Lee WHK (1997). One minute after: strong motion map, effective epicenter, and effective magnitude. Bull. Seism. Soc. Am., vol 87, p 1209-1219.
Wu YM, Shin TC, Chen CC, Tsai YB, Lee WHK, and Teng TL (1997). Taiwan rapid earthquake information release system. Seism. Res. Letters, vol 68, p 931-943.
Address questions to the author to: Willie Lee.c/o U.S. Geological Survey, MS-977, 345 Middlefield Road, Menlo Park, CA 94025. (650) 329-4781 email to Willie
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