Applying Dynamic Rupture Simulations in Seismic Hazard Analysis

Abstract:

Numerical simulations of earthquakes enable a careful inspection of dynamic processes and effects which are overlooked in static source representation and ground shaking predictions. Such simulations illuminate patterns of transient stress and seismic wave radiation during rupture propagation and arrest, and they highlight important effects such as rupture directivity. Comparing standard calculations of shaking patterns with those based on dynamic rupture simulations reveals great discrepancies in the shaking intensity and distribution. Observations of asymmetric intensity patterns in various earthquakes also support the need to account for dynamic effects and heterogeneities in future hazard analyses. Simulations with material heterogeneities and interfaces also yield insights into surprising rupture observations such as remotely triggered seismicity and rupture jumps over large stepover zones. Presented here are two case studies of simple applications of dynamic rupture models in seismic hazard studies. First, a simple but robust procedure is proposed to account for the dynamic directivity effect in ground motion maps calculated using a static line source model. The procedure includes characterising shaking amplification patterns in a range of dynamic rupture models and comparing them with ground motion maps derived using common seismic hazard software. We find that the area in which any certain PGA level is expected is greatly underestimated if calculations are based on static point/line source models. We demonstrate this with results from a seismic hazard study of Eilat, Israel. We also present dynamic rupture simulations used in an analysis of plausible and maximal rupture lengths expected along Dead Sea Transform. Evaluating geophysical and geomorphological data from two large stepovers we assess if a large multi-segment earthquake is likely in light of numeric results that show how heterogeneities and dynamic effects enable large rupture jumps.