New perspectives on self-similarity for shallow thrust earthquakes

TitleNew perspectives on self-similarity for shallow thrust earthquakes
Publication TypeJournal Article
Year of Publication2016
AuthorsDenolle M.A, Shearer PM
JournalJournal of Geophysical Research-Solid Earth
Volume121
Pagination6533-6565
Date Published2016/09
Type of ArticleArticle
ISBN Number2169-9313
Accession NumberWOS:000385845700016
KeywordsEarthquake dynamics; earthquake source spectra; earthquakes; great earthquakes; ground motion; m-w-greater-than-or-equal-to-7.0 megathrust; megathrust earthquake; radiated energy; rupture characteristics; self-similarity; source parameters; source spectra; source time functions; stress drop; stress-drop; strong; subduction zone earthquakes; sumatra-andaman earthquake
Abstract

Scaling of dynamic rupture processes from small to large earthquakes is critical to seismic hazard assessment. Large subduction earthquakes are typically remote, and we mostly rely on teleseismic body waves to extract information on their slip rate functions. We estimate the P wave source spectra of 942 thrust earthquakes of magnitude M-w 5.5 and above by carefully removing wave propagation effects (geometrical spreading, attenuation, and free surface effects). The conventional spectral model of a single-corner frequency and high-frequency falloff rate does not explain our data, and we instead introduce a double-corner-frequency model, modified from the Haskell propagating source model, with an intermediate falloff of f(-1). The first corner frequency f(1) relates closely to the source duration T-1, its scaling follows M0T13for M-w<7.5, and changes to M0T12 for larger earthquakes. An elliptical rupture geometry better explains the observed scaling than circular crack models. The second time scale T-2 varies more weakly with moment, M0T25, varies weakly with depth, and can be interpreted either as expressions of starting and stopping phases, as a pulse-like rupture, or a dynamic weakening process. Estimated stress drops and scaled energy (ratio of radiated energy over seismic moment) are both invariant with seismic moment. However, the observed earthquakes are not self-similar because their source geometry and spectral shapes vary with earthquake size. We find and map global variations of these source parameters.

DOI10.1002/2016jb013105
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