Testing Transient Triggering of Earthquakes with Aftershock Spatial Distributions

University Of Memphis, Memphis TN

Investigators

Abstract

The objective of this proposal is to illuminate the relative importance of the transient and permanent components of stress perturbations in triggering earthquake aftershocks. The PI proposes to undertake a study of the global scale that uses existing data. The simple notion that underlies the proposed work follows previous research on triggering of aftershocks by the Landers earthquake. For earthquakes that feature unilateral rupture propagation, permanent (static) stress changes are spatially symmetric while peak transient (dynamic) stresses are asymmetric. This difference provides a means to study the relative roles of each of these components of stress perturbations. The proposed work will seek to determine whether a systematic relationship exists between the spatial symmetries of aftershock distributions and the propagation characteristics (rupture directivity) of the mainshock. The research will: 1) survey databases and the literature to determine which earthquakes have both reliable estimates of directivity effects (or their absence), and statistically reliable aftershock (and before mainshock) catalogs, and 2) devise and apply metrics that compare the spatial distribution of stress fields with aftershock occurrence patterns, focussing on spatial symmetry or asymmetry. Additional research steps will also be included, such as waveform modeling of at least some earthquakes to constrain models of dynamic stresses at seismogenic depths and numerical elastic modeling to estimate the static stress field changes.