%AGong, Wenzheng [Department of Earth and Space Sciences Southern University of Science and Technology Shenzhen China]%AYe, Lingling [Department of Earth and Space Sciences Southern University of Science and Technology Shenzhen China]%AQiu, Yuxin [Department of Earth and Space Sciences Southern University of Science and Technology Shenzhen China]%ALay, Thorne [Department of Earth and Planetary Sciences University of California Santa Cruz Santa Cruz CA USA]%AKanamori, Hiroo [Seismological Laboratory California Institute of Technology Pasadena CA USA]%BJournal Name: Journal of Geophysical Research: Solid Earth; Journal Volume: 127; Journal Issue: 9; Related Information: CHORUS Timestamp: 2023-11-26 15:09:23 %D2022%IDOI PREFIX: 10.1029 %JJournal Name: Journal of Geophysical Research: Solid Earth; Journal Volume: 127; Journal Issue: 9; Related Information: CHORUS Timestamp: 2023-11-26 15:09:23 %K %MOSTI ID: 10373475 %PMedium: X %TRupture Directivity of the 2021 M W 6.0 Yangbi, Yunnan Earthquake %XAbstract

The 2021MW6.0 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 ∼. The relatively low moment scaled radiated energyof 1.5 × 10−5and 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.

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