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

Sylvain Michel, Jean Philippe Avouac, Nadia Lapusta, Junle Jiang

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Megathrust earthquakes tend to be confined to fault areas locked in the interseismic period and often rupture them only partially. For example, during the 2015 M7.8 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 (>1 Hz) 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.

Original languageEnglish
Pages (from-to)8345-8351
Number of pages7
JournalGeophysical Research Letters
Volume44
Issue number16
DOIs
Publication statusPublished - 28 Aug 2017

Keywords

  • Gorkha earthquake
  • High Frequency Radiation
  • Main Himalayan Thrust
  • Megathrusts
  • Partial Ruptures
  • Pulse

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