This electronic supplement contains four figures and two tables. Figures show fault-slip models, checkerboard tests, and comparison of observed, predicted, and residual interferograms, and tables of the ALOS2 images used and fault-slip distribution of the 2015 Mw 6.4 Pishan earthquake.
The figures show the slip distribution and resolution test results of the slip models. Fault-slip model of the Sentinel-1A (S1A) data only (model A) and of the S1A and ALOS2 data (model B) are displayed in Figure S1. To assess the resolution of the slip models, we conducted two checkerboard tests in this study. In the first test, we generated displacements of all Interferometric Synthetic Aperture Radar (InSAR) observations based on a hypothesized ~Mw 6.5 event with two different sizes of asperities (4 × 5 km2 and 4 × 20 km2 uniform slip of 1 m) in the dip slip (Fig. S2). The InSAR data were assigned the same uncertainties as were used in the final model. We inverted a best-fitting solution by adjusting the smoothness parameter while retaining all the other parameter settings. Differences between the input and output slip models indicate that our dataset can capture the slip at depths ≤15 km, especially at a scale of 4 × 20 km2. This test also indicates that the resolution slowly decreases as the depth increases from 7 to 15 km, so we can still get a reasonable resolution even when the asperity is located at depth up to 13 km. In the second test, we repeated the test above with a different slip pattern as shown in Figure S3. Its result also demonstrates a reasonable resolution in retrieving the deep asperity. These two tests confirm that the slip can be well resolved in both size and pattern (Figs. S2 and S3). Interferograms, models, and residuals based on slip model A were shown in Figure S4. The Synthetic Aperture Radar data used and the final fault-slip distribution inverted were listed in Tables S1 and S2.
Figure S1. Fault-slip model of the S1A data only (model A) and S1A and ALOS2 data (model B).
Figure S2. Checkerboard test with the same slip value but different numbers of asperities.
Figure S3. Checkerboard test with different values and different numbers of asperities.
Figure S4. Interferograms, models, and residuals based on slip model A, estimated from S1A data only.
Table S1. Satellite images used for generating interferogram of coseismic surface deformation and postseismic surface deformation.
Table S2. Fault-slip distribution of the 2015 Mw 6.4 Pishan earthquake.
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