Early warning system for aftershocks
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Abstract
A prototype early warning system to provide San Francisco and Oakland, California a few tens-of-seconds warning of incoming strong ground shaking from already-occurred M ≧ 3.7 aftershocks of the magnitude 7.1 17 October 1989 Loma Prieta earthquake was operational on 28 October 1989. The prototype system consisted of four components: ground motion sensors in the epicentral area, a central receiver, a radio repeater, and radio receivers. One of the radio receivers was deployed at the California Department of Transportation (CALTRANS) headquarters at the damaged Cypress Street section of the I-880 freeway in Oakland, California on 28 October 1989 and provided about 20 sec of warning before shaking from the M 4.5 Loma Prieta aftershock that occurred on 2 November 1989 at 0550 UTC. In its first 6 months of operation, the system generated triggers for all 12 M > 3.7 aftershocks for which trigger documentation is preserved, did not trigger on any M ≦ 3.6 aftershocks, and produced one false trigger as a result of a now-corrected single point of failure design flaw. Because the prototype system demonstrated that potentially useful warnings of strong shaking from aftershocks are feasible, the USGS has completed a portable early warning system for aftershocks that can be deployed anywhere.
Study Area
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Early warning system for aftershocks |
| Series title | Bulletin of the Seismological Society of America |
| DOI | 10.1785/BSSA0840020359 |
| Volume | 84 |
| Issue | 2 |
| Year Published | 1994 |
| Language | English |
| Publisher | Seismological Society of America |
| Description | 7 p. |
| First page | 359 |
| Last page | 365 |
| Country | United States |
| State | California |
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