Uncertainties in earthquake magnitudes from surface fault displacement based on finite element modeling

Abstract

Numerical simulation of normal-fault earthquakes was performed using dynamic finite element analysis, to evaluate uncertainties associated with empirical relationships for estimating earthquake magnitude. Simulations involved inducing slip on a steep normal fault and monitoring ground accelerations and displacements. Magnitudes of simulated earthquakes were then estimated using published empirical relationships and compared with magnitudes inferred from seismic slip energy. The results indicate that earthquake magnitudes inferred from ground-surface displacements, using empirical relationships between surface displacement and earthquake magnitude, are likely to underestimate magnitudes of relatively deep earthquakes. On the other hand, the same empirical relationships are likely to overestimate magnitudes of relatively shallow earthquakes.