‘Two go together’: Near-simultaneous moment release of two asperities during the 2016 Mw 6.6 Muji, China earthquake

Bie, Lidong ORCID: https://orcid.org/0000-0002-8130-7084, Hicks, Stephen, Garth, Thomas, Gonzalez, Pablo and Rietbrock, Andreas (2018) ‘Two go together’: Near-simultaneous moment release of two asperities during the 2016 Mw 6.6 Muji, China earthquake. Earth and Planetary Science Letters, 491. pp. 34-42. ISSN 0012-821X

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On 25 November 2016, a Mw 6.6 earthquake ruptured the Muji fault in western Xinjiang, China. We investigate the earthquake rupture independently using geodetic observations from Interferometric Synthetic Aperture Radar (InSAR) and regional seismic recordings. To constrain the fault geometry and slip distribution, we test different combinations of fault dip and slip direction to reproduce InSAR observations. Both InSAR observations and optimal distributed slip model suggest buried rupture of two asperities separated by a gap of greater than 5 km. Additional seismic gaps exist at the end of both asperities that failed in the 2016 earthquake. To reveal the dynamic history of asperity failure, we inverted regional seismic waveforms for multiple centroid moment tensors and construct a moment rate function. The results show a small centroid time gap of 2.6 s between the two sub-events. Considering the >5 km gap between the two asperities and short time interval, we propose that the two asperities failed near-simultaneously, rather than in a cascading rupture propagation style. The second sub-event locates ∼39 km to the east of the epicenter and the centroid time is at 10.7 s. It leads to an estimate of average velocity of 3.7 km/s as an upper bound, consistent with upper crust shear wave velocity in this region. We interpret that the rupture front is propagating at sub-shear wave velocities, but that the second sub-event has a reduced or asymmetric rupture time, leading to the apparent near-simultaneous moment release of the two asperities.

Item Type: Article
Additional Information: Funding Information: We thank the Editor Rebecca Bendick, Christopher W. Johnson and an anonymous reviewer for their insightful comments. This work was partially supported by the UK Natural Environment Research Council (NERC) through the Centre for the Observation and Modeling of Earthquakes, Volcanoes and Tectonics (COMET, GA/13/M/031 ). Lidong Bie is supported by NERC (grant number NE/K010611/1 ). Sentinel-1 Single-Look Complex (SLCs) data were obtained from the European Space Agency (ESA) Copernicus data hub. PALSAR 2 data used in this study was obtained through ALOS RA4 (#PI1054 “Mapping ground surface deformation due to natural hazards using ALOS-2 interferometry”) under a cooperative research contact with JAXA. The PALSAR 2 data belongs to METI and JAXA. Seismic data was obtained from the IRIS Data Management Center. Publisher Copyright: © 2018 The Author(s)
Uncontrolled Keywords: insar,muji earthquake,multiple moment tensor inversion,near simultaneous failure,seismic gap,geophysics,geochemistry and petrology,earth and planetary sciences (miscellaneous),space and planetary science ,/dk/atira/pure/subjectarea/asjc/1900/1908
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Depositing User: LivePure Connector
Date Deposited: 22 Apr 2022 10:30
Last Modified: 13 Nov 2022 07:30
URI: https://ueaeprints.uea.ac.uk/id/eprint/84736
DOI: 10.1016/j.epsl.2018.03.033


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