This electronic supplement includes three tables and one figure to explain the velocity model, an illustration of the relative centroid-location method, and the rupture directivity estimation results.
Table S1. The central U.S. (CUS) velocity model (Herrmann, 1979).
Table S2. The rupture directivity estimation result for the forward test.
Table S3. The rupture directivity estimation result with Love waves for the bilateral rupture test.
Figure S1. A schematic map of the relative centroid-location method. The mainshock (M) ruptures from the hypocenter (Mh) toward the centroid (Mc). For the reference event (A), the hypocenter (Ah) and centroid (Ac) are very close to each other. The reference event is used as a path calibration to suppress the effect of velocity anomaly.
Herrmann, R. B. (1979). Surface wave focal mechanisms for eastern North American earthquake with tectonic implications, J. Geophys. Res. 84, 3543–3552.
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