Electronic Supplement to
Source Characteristics of the 2016 Meinong (M_L 6.6), Taiwan, Earthquake, Revealed from Dense Seismic Arrays: Double Sources and Pulse-Like Velocity Ground Motion

by Yen-Yu Lin, Te-Yang Yeh, Kuo-Fong Ma, Teh-Ru Alex Song, Shiann-Jong Lee, Bor-Shouh Huang, and Yih-Min Wu

This electronic supplement contains seven figures, including the resolution test of the improved source-scanning algorithm (SSA) method (Fig. S1), the comparison of the results between the improved and original SSA methods (Fig. S2), the comparison of waveforms recorded by an accelerometer and a broadband instrument at Station MASB (Fig. S3), the comparison of unfiltered and filtered waveforms of the stations in the south (Fig. S4), the observed waveforms and the predicted synthetic waveforms considering different focal mechanisms for the foreshock (Fig. S5), the comparison of the observations and synthetic waveforms considering M_w 5.5 for the foreshock (Fig. S6), and the distribution of the stations which recorded the large pulse-like velocity ground motions (Fig. S7).

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Figures

Figure S1. Resolution of a synthetic test for the improved SSA method. Upper and lower sections demonstrate the spatial and temporal resolution results, respectively. The green stars in the upper section are the input location, and the arrow in the lower section is the input centroid delay time.

Figure S2. Comparison of the (a) improved and (b) original SSA methods. The upper and lower sections demonstrate the spatial and temporal resolution results, respectively. The green stars in the upper section reveal the best solution of the mainshock. The arrows in the lower section are the best solution for the centroid delay. The color bar in (a) indicates marginal probability, and the color bar in (b) indicates normalized brightness.

Figure S3. Comparison of the velocity waveforms from the accelerometer and broadband instrument in Station MASB. No filter was applied in the records.

Figure S4. Comparison of (a) original velocity east-component waveforms and (b) the waveforms after applying a low-pass filter of 0.33 Hz for the stations in the south of the hypocenter. The arrivals of the P₁, S₁, P₂, and S₂ phases are indicated on the traces.

Figure S5. Comparison of (a) the velocity observations and (b,c) the synthetics for the foreshock in Station MASB. The synthetics are considered as the focal mechanism from (b) the grid search (275/20/15) and (c) the Central Weather Bureau (CWB) focal solution (263/15/−18). No filter was applied in the records.

Figure S6. Comparison of the observation (black line in the upper section) and the S₁-phase synthetic (red line), considering the foreshock’s source parameters (the CWB hypocenter, M_w 5.5, and the focal mechanism 275/20/15) in the MASB records in the east component. The lower section indicates the observation of the M_w 5.05 event from 23 December 2008 (E2008) as a reference. A low-pass filter of 0.33 Hz was applied in all records.

Figure S7. Distribution of the stations recording the large pulse-like velocity ground motions near the city of Tainan.

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