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fig_S1.pdfPDF document1192KVelocity models and corresponding waveform fits. The left panel shows the best Vs and Vp profiles for the various stations with the name of stations indicated on the top of each profile. The right panel shows the waveform fitting between the data (black) and synthetics (red), the name of station is indicated at the beginning of each trace and the above numbers are the peak amplitude of data (front) and synthetics (back). All waveforms have been filtered to 0.02~3 Hz.
fig_S2.pdfPDF document1172KWaveform comparisons of the high-rate GPS stations (upper panel) and strong motion stations (middle panel) for the Mw5.4 event; here the synthetics (red) are generated by the preferred slip model for the Mw5.4 event. Both data and synthetics are filtered to 0.1~3.0 Hz with GPS waveform displayed in displacement and strong motion in velocity. The prediction for the strong motion station 05060 is shown in the lower panel. Because the data were obtained after we have derived the model, they did not include this station in the inversion.
fig_S3.pdfPDF document660KSimilar waveform comparison for the Mw5.3 event (15199681); note that we only used strong motion data in the inversion. See caption of Figure S2 for detailed descriptions.
fig_S4.pdfPDF document1299KResolution test for the inversion set up as used for inverting the real data. A checker-board–like slip model (a) was used to generate synthetics data, a constant rise time (0.6 s) and rupture velocity (2.5 km/s, indicated as iso-rupture time) is assumed in the input model (c). During the inversion, we used the same inversion setup as used for the real data, in which the slip amplitude is searched in the range of 0~100 cm, the rise time can change from 0.05 to 1.05 s and the rupture velocity can vary from 2.0 to 3.0 km/s. The inverted slip model and rise time are shown in Figures S4b and S4c, respectively, the rupture velocity is shown as iso-rupture time in Figure S4c. Note that the rise time is smoothed by averaging the values over the neighboring subfaults, similar as shown in Figure 3.
fig_S5.pdfPDF document519KVertical velocity waveforms of the Mw3.9 (green), Mw5.3 (red), and Mw5.4 events recorded on the closest station Q0044. All the waveforms are not filtered and plotted in absolute amplitude. Note that the M>5 events take 0.5 s or more after initiation to get the largest motions, suggesting the hypocenter is at a region of weak radiation.
fig_S6.pdfPDF document2565KShallow slip sensitivity test for the static and seismic data. (a) The input model has 20 cm of uniform slip distributed in a rectangular region. The iso-rupture time is indicated by the contours. The rise time for each subfault is chosen randomly between 0.1 and 1.0 s. (b) Seismic signals (red) produced by the input model at the three strong motion stations. The data (black) are for the Mw5.4 event with peak amplitude shown at the end of each trace. Note that the synthetics are much higher in amplitude than the data and the waveform similarity is poor, implying little or no coseismic rupture at shallow depths. (c) Static signals (red arrows) produced by the slip model in Figure S6a. The black triangles are the strong motion stations. (d) Three-dimensional static deformation produced by the slip model in Figure S6a, with vertical component indicated by the color bar and horizontal deformations indicated by the white arrows. Note the large signals are concentrated close to the fault, which means the GPS data set has lower resolution to very shallow aseismic creep.
fig_S7.pdfPDF document2770KInterferometric synthetic aperture radar data fitting by model predictions. (a) Line of sight (LOS) displacement prediction for ascending TerraSAR-X interferogram (A015) by the combined slip models for the Mw5.3 and Mw5.4 events; the synthetics have been multiplied by a constant (1/0.7) to account for the difference between the moment of the largest two events and the entire swarm. The red star indicates the epicenter of the Mw5.4 event and the rectangle is the map projection of the fault plane. Red circles are the nearby GPS stations and the red dashed line indicates the approximate plate boundary between the Pacific and North America plate. Prediction from the hypothetical slip model in Figure S6 is shown in Figure S7c. The corresponding TerraSAR-X ascending track interferogram for 2012/08/09–08/31 is shown in Figure S7e and the black line shows the location of the center of a swath (with width of 4 km). The looking angle from vertical is 26.3° (at center) and the azimuth is 78°. (g) The interferometric synthetic aperture radar phase converted to range-change is shown in gray in the swath profile. The heavy black line is the average within the swath, the red line is the model prediction along the black line in Figure S7a, and the green line is prediction along the black line in Figure S7c. (b, d, f, and h) Similar plots for the descending interferogram (D068) of 2012/08/12–09/03. The looking angle from vertical is 28.9° (at center) and the azimuth is –78°. Original TerraSAR-X data are copyright 2012 DLR. Note the sharpness of the predictions in Figures S7g and S7h from the hypothetical slip model.
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