Probabilistic analysis of seismic hazards in southwest Indiana

Lin Zhao, Purdue University


The relative contributions of seismic hazards produced by the New Madrid Seismic Zone (NMSZ) and the Wabash Valley Seismic Zone (WVSZ) were quantified through probabilistic seismic hazard analysis (PSHA). A total of 39 sites in southwest Indiana and surrounding Illinois and Kentucky were selected to conduct PSHA. The PSHA results suggest that the WVSZ has a much higher contribution of peak acceleration (PA) and spectral accelerations (SA) at 0.2 and 0.3 sec to southwest Indiana than does the NMSZ. Therefore, earthquakes from the WVSZ will produce more damage to southwest Indiana than those from the NMSZ. Probabilistic seismic hazard maps for soil were developed by mapping ground motion amplification. This study performed Level II mapping using a one-dimensional ground response analysis of uniform, damped soil on elastic rock. The PSHA results for soil suggest that earthquakes in both the WVSZ and the NMSZ are able to cause damage in southwest Indiana. Seismic microzonation assessment of earthquake-induced settlement and of ground motion amplification for Evansville has been performed in this study. Soils in some sites are prone to settle during earthquakes. Earthquakes in the WVSZ will produce more damage than those in the NMSZ since they will induce larger settlement and influence larger areas. Soils in Evansville have different site responses for earthquakes in the WVSZ and the NMSZ. PA of earthquakes in the NMSZ is amplified in Evansville. PA of earthquakes in the WVSZ is amplified at some sites but reduced in other sites. The ranking of damage from ground motion and soil liquefaction are integrated using a Geographic Information System. Damage index maps suggest that east and north Evansville have a smaller damage index than do downtown and west Evansville. This study presents a preliminary assessment of earthquake hazards in southwest Indiana. Limitations of this study are associated with the earthquake catalog, geologic knowledge and methodologies. Therefore, more studies are needed to advance the understanding of earthquake hazards in southwest Indiana.




West, Purdue University.

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