Speaker: Rachel Abercrombie, Earth and Environment, Boston University
Title: Improving Earthquake Stress Drop Estimates to Constrain Rupture Dynamics and Fault Heterogeneity
Host: Zhe Jia
Abstract: Small earthquakes contain a wealth of information about active structures, and the state of stress in the earth, not least because they are so numerous. The stress release (or stress drop) during an earthquake provides fundamental information about the energy budget, and the slip and area of rupture, which are needed to investigate earthquake triggering and rupture dynamics. Stress drop is also an important element of seismic hazard forecasting since high stress drop earthquakes radiate more high frequency energy, resulting in stronger ground shaking. However, in practice stress drop has proved notoriously hard to measure reliably. Estimates by different researchers, using different methods or datasets, have yielded highly inconsistent values. This wide scatter masks physical trends (such as depth, mechanism, regional variation, or dependence on fault heterogeneity) that may identify the factors governing earthquake rupture.
I will discuss recent work by myself and others focused on improving stress drop estimates, and investigating the uncertainties resulting from modelling assumptions and the ambiguity of separating source and path effects in recorded seismograms. A consistent observation is that there is more small-scale spatial variability and complexity within one individual sequence, than there is between earthquakes in different tectonic settings.