Segmentation of the Sumatran Fault Zone based on spatial variation of b- values

Potential seismic hazards in the Sumatran Fault Zone (SFZ) have been highlighted as a consequence of significant earthquakes ( M W ≥ 6.5). Fault geometry might control the initiation and propagation of rupture, which develops the importance of fault segmentation on the SFZ. In the last two decades, SFZ segments have been proposed through geological observations of surface traces using fractal and structural discontinuity analysis and seismic using seismicity clustering. This study presents a new insight into segmenting the SFZ using b -value changes through the maximum likelihood analysis to represent the characterization of the fault. We mapped a spatial analysis of b -values using a catalog of 681 shallow earthquakes with a moment magnitude ( M W ) between M W 3.0 and M W 5.6 with a standard error (σ_M_W) of ± 0.21, estimated by applying the spectral analysis method. We get the average of b -value along the SFZ, which is quite low at 0.9 with a standard error (σ_b) of ± 0.031. The lowest b -value ( b = 0.74) was observed in northern Sumatra (S1), and the highest b -value ( b = 1.39) was in central Sumatra (S5). We analyzed the pattern of b -values changes spatially toward seismicity distribution. Based on b -value changes, we obtained the SFZ divided into 15 segments which describe a pattern of heterogeneity of b -value in characterizing the faults. These results provide a new perspective in explaining potential areas of seismic hazard along the segment of SFZ.