THE ROLE OF PALEOLIQUEFACTION STUDIES IN PERFORMANCEBASED EARTHQUAKE ENGINEERING IN THE CENTRAL-EASTERN UNITED STATES

摘要

The implementation of performance-based earthquake engineering requires determination of both the fragility of structural systems and the probabilistic seismic hazard. In regions of low-to-moderate seismicity, such as the central and eastern United States (CEUS), the historic earthquake record is too short to determine the magnitude recurrence relationship for earthquakes larger than approximately M4.5. Thus, probabilistic quantification of the seismic hazard is greatly impeded. Paleoseismology utilizing paleoliquefaction investigations is a viable approach to extend the earthquake record to prehistoric times in the CEUS, allowing the recurrence time of moderate-to-large earthquakes to be established. However, previous interpretations of prehistoric strength of shaking using these liquefaction effects have been questionable because of the lack of having appropriate geotechnical techniques. The authors have recently developed both field and analytical techniques, outlined in Obermeier [1], Olson [2], and Green [3], which we believe should resolve these deficiencies. As a case-history example illustrating our new methods, we re-assessed the magnitude of the Vincennes earthquake that occurred in the Wabash Valley (southern Illinois/Indiana) about 6,100 years BP to be approximately M7.5. Similar assessments could be used in other relatively high seismic regions of the CEUS, such as Charleston, South Carolina and the New Madrid Seismic Zone. Our new techniques are applicable in many field settings, worldwide, irrespective of tectonic setting.