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Published August 28, 2017 | Supplemental Material + Published
Journal Article Open

Pulse-Like Partial Ruptures and High-Frequency Radiation at Creeping-Locked Transition during Megathrust Earthquakes

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.

Additional Information

© 2017 American Geophysical Union. Received 26 JUN 2017; Accepted 10 AUG 2017; Accepted article online 16 AUG 2017; Published online 31 AUG 2017. The data used are listed in the supporting information. We thank Yen-Yu Lin for his help with the numerical code. We thank Adriano Gualandi, James Jackson, and Alex Copley for discussions. This research was partially funded by the National Science Fundation throuh grant EAR 1345136.

Attached Files

Published - Michel_et_al-2017-Geophysical_Research_Letters.pdf

Supplemental Material - grl56308-sup-0001-2017GL074725_SI.pdf

Supplemental Material - grl56308-sup-0002-2017GL074725_ms01.mp4

Supplemental Material - grl56308-sup-0003-2017GL074725_ds01.rar

Supplemental Material - grl56308-sup-0004-2017GL074725_ds02.rar

Supplemental Material - grl56308-sup-0005-2017GL074725_ds03.rar

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August 21, 2023
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October 17, 2023