Early warning system for aftershocks

W. H. Bakun; F.G. Fischer; E.G. Jensen; J. VanSchaack

doi:10.1785/bssa0840020359

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Early warning system for aftershocks

W. H. Bakun·F.G. Fischer·E.G. Jensen·J. VanSchaack

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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.

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Bulletin of the Seismological Society of America Article

Source-reported bounding extent: 35.93080870601099° to 38.63998260571137° latitude; -123.22332656538535° to -119.83953750288532° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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BibTeX RIS

W. H. Bakun, F.G. Fischer, E.G. Jensen, J. VanSchaack. 1994. Early warning system for aftershocks. https://doi.org/10.1785/bssa0840020359

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