Previous studies (Pinel-Puysségur et al., 2014; Pezzo et al., 2014) have suggested a straight fault geometry, and our data did not strongly indicate curved geometries either. Therefore, we first tested different depths and dip angles, by keeping the strike of all the faults straight. However, significant residuals remained, especially in the descending data, even for the best straight fault model (Figs. S1, S2). To resolve these unexplained signals, we carefully examined the data, and found that the descending observation in Fig. 4a suggests a clear bend in RLF1 around the central point. In addition, RLF2 exhibits a curved strike. The modeling conducted by following the curved geometry for right lateral faults (RLF1 and RLF2), explained the observed deformation quite successfully (Figs. 3, 4, 9).
Examination of the fault mechanism solutions (Fig. 2) suggests that the strike-slip contribution was more dominant than the dip-slip component of the main shocks and most of the aftershock crustal deformation. The maximum observed magnitudes were 6.4 and 6.4 (Mw) for the main shocks and 5.7 (Mw) for the aftershocks (Table 1). Thus, for the source modeling, we attempted to produce a model that exhibits nearly the same characteristics in terms of slip components, and calculated the magnitudes along with minimum possible residuals and logical slip distributions.
As it was established that LLF1 contributed to the crustal deformations resulting from both the main shocks and aftershocks, we produced an optimum fault model (Figs. 5 and 10) by following a trial-and-error process, i.e., various possibilities related to the depth and dip of LLF1 were analyzed, and the best result was selected. LLF1, with the same geometry, was imported to the co-seismic model, and again, a trial-and-error process was performed by changing the depths and dip angles of RLF1, RLF2, and LLF2. The best model selected (Figs. 3, 4, and 10) has a strike-slip component dominating over the dip-slip, with maximum slip distributed along conjugate faults (RLF1 and LLF1), and the calculated magnitudes (Mw) are 6.3 for LLF1 and 6.5 for RLF1, very close to the observed moment magnitudes.
Figure S1. Modeling results following straight fault geometry; areas enclosed in rectangular boxes in the descending and ascending observation are shown in Figs. 6 and 7.
Figure S2. Slip distribution for the seismic sequence (faults with straight strikes). The top of the faults is 300 m below the crust surface. The calculated magnitudes (Mw) for RLF1, RLF2, LLF1, and LLF2 are 6.3, 6, 6.3 and 5.8, respectively.