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Predicting Strong Ground Motion from Weak Ground Motion


IPGP - Îlot Cuvier


Séminaires de Sismologie

Salle 310

Greg Beroza


Predicting strong ground motion from future earthquakes is among the most important research topics in seismology. Ground motion prediction equations express relationships between earthquake and site properties and some measure of ground motion intensity. In some locations there is little data to constrain these relationships. For all areas there are few records of ground motion available to characterize the level and variability of ground motion close to large earthquakes. As a result, seismologists are increasingly turning to simulations to predict strong ground motion. Validating the accuracy of these simulations is critically important. My research group has developed two new approaches for strong ground motion prediction. Both methods rely on data that is approximately one million times weaker in amplitude than the strong ground motion of interest. The first method uses tectonic tremor to constrain the amplitude decay with distance of seismic waves in subduction zones. The abundant tremor data should allow us to explore the variability of ground motion with distance both regionally, and between different subduction zones. The second method uses the ambient seismic field to construct virtual earthquakes that predict spatial variations in long period strong ground motion for scenario earthquakes. Neither of these approaches is a full solution, because they do not address the initial wave excitation by earthquake faulting, nor nonlinearity due to plastic deformation off the fault. What they do address, is the complex linear wave propagation effects exerted by the complex geology of the Earth’s crust on seismic wavefields.