Strong ground motions from two historical earthquakes
McKenna, Jonathan P
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Strong ground motions recorded throughout the San Francisco Bay Area from the Loma Prieta earthquake (1989) and the San Francisco earthquake (1906) show high correlations with sediment/soil characteristics. Transverse, radial and vertical acceleration compiled by the Strong Motion Database (SMDB) and shake maps produced by the Association of Bay Area Governments (ABAG) have been used to analyze the relationship between ground motion and the subsurface. Modified Mercalli Intensity (MMI) reveals better results than peak ground acceleration (pga). Pearson’s correlation coefficient reveals general trends including a positive relationship between ground motion and depth to bedrock, drainage class, clay content, and texture and a negative relationship for age of deposit. Both cumulative logistic and multiple regression models show no simple relationship between MMI and distance from the earthquake epicenter as predicted by the Joyner-Boore model, suggesting other variables play a greater role in ground motion. Probabilistic seismic hazard maps and strong ground motion susceptibility maps are produced for a repeat of both earthquakes.