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Pulse-like partial ruptures and high-frequency radiation at creeping-locked transition during megathrust earthquakes

TitlePulse-like partial ruptures and high-frequency radiation at creeping-locked transition during megathrust earthquakes
Publication TypeJournal Article
Year of Publication2017
AuthorsMichel S., Avouac J.P, Lapusta N., Jiang J.L
JournalGeophysical Research Letters
Date Published2017/08
Type of ArticleArticle
ISBN Number0094-8276
Accession NumberWOS:000410658800031
Keywords2015 gorkha earthquake; dynamic rupture; earthquake; fault; gorkha; High Frequency Radiation; main himalayan; main himalayan thrust; Megathrusts; nepal; Partial Ruptures; physics; Pulse; slip; thrust; velocity-weakening friction; zone

Megathrust earthquakes tend to be confined to fault areas locked in the interseismic period and often rupture them only partially. For example, during the 2015M7.8 Gorkha earthquake, Nepal, a slip pulse propagating along strike unzipped the bottom edge of the locked portion of the Main Himalayan Thrust (MHT). The lower edge of the rupture produced dominant high-frequency (>1Hz) radiation of seismic waves. We show that similar partial ruptures occur spontaneously in a simple dynamic model of earthquake sequences. The fault is governed by standard laboratory-based rate-and-state friction with the aging law and contains one homogenous velocity-weakening (VW) region embedded in a velocity-strengthening (VS) area. Our simulations incorporate inertial wave-mediated effects during seismic ruptures (they are thus fully dynamic) and account for all phases of the seismic cycle in a self-consistent way. Earthquakes nucleate at the edge of the VW area and partial ruptures tend to stay confined within this zone of higher prestress, producing pulse-like ruptures that propagate along strike. The amplitude of the high-frequency sources is enhanced in the zone of higher, heterogeneous stress at the edge of the VW area.

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