THE CHARACTERISTICS OF EARTHQUAKE SOURCE ZONES AND DISTRIBUTION OF B VALUES ALONG THE SUMATRAN FAULT, INDONESIA

• Main Author: Surya Putra, Ade
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77506
• Institution: Institut Teknologi Bandung

The potential seismic hazard in the Sumatra Fault Zone (SFZ) has been highlighted as a consequence after a sequence of megathrust earthquakes in the subduction zone (2004 ????????9.2 Sumatra-Andaman, 2005 ????????8.6 Nias-Simeulue, and 2007 ????????8.4 Bengkulu). Even on the 2017 Indonesia earthquake hazard map, there are increasement report in risk hazards locally near active crustal faults, including faults with multi-segments such as SFZ. SFZ segments have been proposed through various observations such as with geological structural discontinuities, using fractal analysis as well and through seismicity using seismicity clustering. In this study we added analysis of earthquake sources by grouping each spatial change of b-values along the estimated SFZ with maximum likelihood analysis to represent the characterization of seismicity in each group. We mapped the spatial analysis of b-values using a catalogue of 681 shallow earthquakes with moment magnitudes (????????) between ????????3.0 and ????????5.6 with standard faults (????(????????)) ±0.21, estimated by applying spectral analysis methods. We get the average b-value along the SFZ quite low at 0.9 with a mean error (????????? ) of ±0.031. The lowest b-value (b = 0.74) observed in northern Sumatra (S1) and the highest b-value (b = 1.39) were in central Sumatra (S5). We analyze the pattern of changes in b-values spatially towards seismicity distribution. Based on the change in b-value, we obtain an SFZ divided into 15 earthquake source zones illustrates a pattern of seismogenic cluster and heterogeneity of the b-values. These results add to the explanation of potential seismic hazards along the SFZ segment.