Ground Motion: Complexity and Scaling in the Near Field of Earthquake Ruptures

Paul M. Mai

Under Review 2008, SCEC Contribution #1154

The accurate prediction of the level and variability of (potentially damaging) near-source strong-ground motions in future earthquakes is one of the key challenges for seismologists and earthquake engineers alike. The increasing number of near-source recordings collected by a variety of dense strong-motion observation arrays exemplifies the inherent complexity of near-field ground shaking, governed by a number of (partially interacting) physical processes. Characterizing, quantifying, and modeling (either by means of empirical scaling relations or by numerical simulations) ground-motion complexity requires the joint investigation of three dominant ingredients: (I) the physics of earthquake rupture; (II) the details of wave-propagation in heterogeneous media; (III) the effects of local site conditions.

This article discusses briefly the beginnings of strong-motion seismology and recognition of ground-motion complexity. Using two particularly well recorded recent earthquakes, I introduce some observational aspects of near-field ground shaking and the basic mathematical description for computing ground motion, focusing on source and path effects. The article proceeds by describing each of these “ground-motion ingredients” in some detail, but does not attempt to provide an in-depth review of all the scientific advancements in these fields. Rather, I explain the key elements for characterizing and modeling ground-motion complexity, supplemented with a concise overview of the underlying physical processes. Current and future research will increasingly incorporate these concepts into standard practice, eventually leading to advanced strong-motion simulation approaches to accurately predict not only the intensity, but also the variability of near-source ground motions.

Mai, P. M. (2008). Ground Motion: Complexity and Scaling in the Near Field of Earthquake Ruptures, (under review).