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Use of Scenario Earthquakes for Seismic Hazard Assessment in the Central United States

Session: How Should Low-Probability Earthquakes be Considered in Hazard Assessments?

Type: Oral

Date: 4/23/2021

Presentation Time: 10:45 AM Pacific

Description: 

Moderate-sized crustal earthquakes originating close to populated areas can have grave impacts on the built environment in the mid-continental United States. While large earthquakes have been documented in this intraplate area in the historic and paleoseismic record, they occur too infrequently to provide reliable observations of earthquake-related impacts. We present here four deterministic scenarios that could affect Indiana residents; a M7.3 Wabash Valley event in southern Illinois, a M6.2 event in west-central Ohio, a M6.2 event near Evansville and a M5.8 central Indiana event near Indianapolis. The locations and magnitudes were based on known fault locations and credible interpretations of the earthquake history in the region. We used a combination of the US Geological Survey’s ShakeMap and FEMA’s Hazus-MH software packages to assess earthquake-triggered ground-shaking and its effect on the built environment. We also used a recently developed ground failure estimation tool to examine the spatial distribution of anticipated earthquake-induced landslide and liquefaction probabilities. Our results indicate that the state’s built environment is significantly vulnerable to these moderate-sized urban earthquakes, which could lead to hundreds of casualties and tens of billions of dollars in economic losses. Deterministic case studies are by definition arbitrary scenarios representing individual cases of a virtually infinite set of possible combinations of earthquake location, magnitude, source type, depth, and wave propagation characteristics that might influence the impact of earthquakes. To gain better understanding on which parameters have the greatest influence on impacts, we conducted a sensitivity analysis for earthquakes near Indianapolis and Evansville, where we reviewed losses due to differences in magnitude, depth, strike, and dip. We found that magnitude and depth have first-order influence on losses and the orientation and dip of the causative fault in relation to populated areas can increase economic losses for an event of the same magnitude by 20-35%.

Presenting Author: Elizabeth M. Sherrill

Student Presenter: Yes

Authors