ENHANCED EVALUATION OF EJECTED MATERIALS FROM EARTHQUAKE INDUCED PALEOLIQUEFACTION FEATURES USING GROUND PENETRATING RADAR

Egan, Marilyn, Haydar J. Al-Shukri, Department of Applied Science, University of Arkansas at Little Rock, Little Rock, AR 72204

The study of paleoseismological features has proven to be an important tool in interpreting both the historical and potential seismic hazards in many regions. In the Central United States the study of paleoliquefaction features, primarily sand blows, has contributed to our understanding of return periods and potential consequences of recurrent large magnitude seismicity. The most common method of detecting these features is to examine riverbanks and ditches. However, significant sand blows have been detected by aerial survey of areas not related to the present day waterways. These landforms present a special challenge for detailed study. Access is often limited to short duration trenching projects that are both costly and provide a limited three-dimensional view of the overall structure. Ground Penetrating Radar (GPR) has been successfully employed in Eastern Arkansas in initial site studies to determine if a locality warrants further examination, to augment data recovered during trench studies, to calculate volume of ejected materials, and to visualize subsurface features at untrenched locations. In addition, some sand dykes present enough physical properties contrast to indicate optimal trench placement. Buried objects and depth to the water table may be visualized as well. GPR is a valuable tool when investigating paleoliquefaction sites.