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Rupture Directivity of the 2021 M_W 6.0 Yangbi, Yunnan Earthquake

Gong, Wenzheng and Ye, Lingling and Qiu, Yuxin and Lay, Thorne and Kanamori, Hiroo (2022) Rupture Directivity of the 2021 M_W 6.0 Yangbi, Yunnan Earthquake. Journal of Geophysical Research. Solid Earth, 127 (9). Art. No. e2022JB024321. ISSN 2169-9313. doi:10.1029/2022jb024321.

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The 2021 M_W 6.0 Yangbi, Yunnan strike-slip earthquake occurred on an unmapped crustal fault near the Weixi-Qiaoho-Weishan Fault along the southeast margin of the Tibetan Plateau. Using near-source broadband seismic data from ChinArray, we investigate the spatial and temporal rupture evolution of the mainshock using apparent moment-rate functions (AMRFs) determined by the empirical Green's function (EGF) method. Assuming a 1D line source on the fault plane, the rupture propagated unilaterally southeastward (∼144°) over a rupture length of ∼8.0 km with an estimated rupture speed of 2.1 km/s to 2.4 km/s. A 2D coseismic slip distribution for an assumed maximum rupture propagation speed of 2.2 km/s indicates that the rupture propagated to the southeast ∼8.0 km along strike and ∼5.0 km downdip with a peak slip of ∼2.1 m before stopping near the largest foreshock, where three bifurcating subfaults intersect. Using the AMRFs, the radiated energy of the mainshock is estimated as ∼1.6 x 10^(13)J. The relatively low moment scaled radiated energy (E_R)/(M_0) of 1.5 × 10^(−5) and intense foreshock and aftershock activity might indicate reactivation of an immature fault. The earthquake sequence is mainly distributed along a northwest-southeast trend, and aftershocks and foreshocks are distributed near the periphery of the mainshock large-slip area, suggesting that the stress in the mainshock slip zone is significantly reduced to below the level for more than a few overlapping aftershock to occur.

Item Type:Article
Related URLs:
URLURL TypeDescription
Gong, Wenzheng0000-0001-6078-3498
Ye, Lingling0000-0001-9689-4149
Lay, Thorne0000-0003-2360-4213
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:We thank editor Rachel Abercrombie, associate editor, and two anonymous reviewers for helpful comments on the manuscript. We also appreciate the initial discussion about the earthquake sequence and encouragement about this study from Xiaofei Chen at Southern University of Science and Technology in China. Lingling Ye's earthquake study is supported by National Natural Science Foundation of China (No. 41874056). Thorne Lay's research on earthquake processes is supported by National Science Foundation Grant EAR1802364.
Group:Seismological Laboratory
Funding AgencyGrant Number
National Natural Science Foundation of China41874056
Issue or Number:9
Record Number:CaltechAUTHORS:20221003-756400000.22
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:117212
Deposited By: Melissa Ray
Deposited On:05 Oct 2022 16:24
Last Modified:05 Oct 2022 16:24

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