ESTIMATING TIMING AND CHARACTERISTICS OF PALEOEARTHQUAKES FROM PALEOLIQUEFACTION DATA

Paleoliquefaction studies contribute a longer view of the seismic behavior of earthquake source areas and fault zones than afforded by the historical period alone, especially in intraplate tectonic settings where large earthquakes occur infrequently. In this presentation, we review methods used to estimate timing, location, magnitude, and recurrence time of paleoearthquakes from liquefaction data and discuss ways to reduce the inherent uncertainties associated with these data. We draw examples from paleoliquefaction studies in the U.S. and Canada, including the New Madrid, Charleston, Charlevoix, and Passamaquoddy Bay seismic zones. We describe key elements of paleoliquefaction studies that include

• Diagnostic criteria for identification of earthquake-induced liquefaction features;
• Sedimentary and structural relationships of liquefaction features indicative of clustered earthquakes;
• Methods for obtaining well-constrained ages of liquefaction features for estimating timing of paleoearthquakes;
• Methods for correlating similar-age features across a region to constrain paleoearthquake source areas and magnitudes;
• Modern and/or historical analogues of earthquake-induced liquefaction for developing empirical magnitude-distance relations and interpreting paleoliquefaction data.