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Title: The mechanism of partial rupture of a locked megathrust: The role of fault morphology
Authors: Qiu, Qiang
Hill, Emma Mary
Barbot, Sylvain
Hubbard, Judith
Feng, Wanpeng
Lindsey, Eric Ostrom
Feng, Lujia
Dai, Keren
Samsonov, Sergey V.
Tapponnier, Paul
Keywords: Earthquakes
Issue Date: 2016
Source: Qiu, Q., Hill, E. M., Barbot, S., Hubbard, J., Feng, W., Lindsey, E. O., et al. (2016). The mechanism of partial rupture of a locked megathrust: The role of fault morphology. Geology, 44(10), 875-878.
Series/Report no.: Geology
Abstract: Assessment of seismic hazard relies on estimates of how large an area of a tectonic fault could potentially rupture in a single earthquake. Vital information for these forecasts includes which areas of a fault are locked and how the fault is segmented. Much research has focused on exploring downdip limits to fault rupture from chemical and thermal boundaries, and along-strike barriers from subducted structural features, yet we regularly see only partial rupture of fully locked fault patches that could have ruptured as a whole in a larger earthquake. Here we draw insight into this conundrum from the 25 April 2015 Mw 7.8 Gorkha (Nepal) earthquake. We invert geodetic data with a structural model of the Main Himalayan thrust in the region of Kathmandu, Nepal, showing that this event was generated by rupture of a décollement bounded on all sides by more steeply dipping ramps. The morphological bounds explain why the event ruptured only a small piece of a large fully locked seismic gap. We then use dynamic earthquake cycle modeling on the same fault geometry to reveal that such events are predicted by the physics. Depending on the earthquake history and the details of rupture dynamics, however, great earthquakes that rupture the entire seismogenic zone are also possible. These insights from Nepal should be applicable to understanding bounds on earthquake size on megathrusts worldwide.
ISSN: 0091-7613
DOI: 10.1130/G38178.1
Rights: © 2016 The Authors. Gold Open Access: This paper is published under the terms of the CC-BY license.
Fulltext Permission: open
Fulltext Availability: With Fulltext
Appears in Collections:EOS Journal Articles

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