Four Earthquakes of the Sumatran Fault Zone (Mw 6.0-6.4): Source Parameters and Identification of the Activated Fault Planes
Madlazim and B.J. Santosa
Four earthquakes (Mw 6.0-6.4) which occurred at 3 major segments of Sumatran Fault Zone (SFZ) were analyzed to identify their fault planes. The events were relocated to assess physical insight into the hypocenter uncertainty. The earthquake source parameters were determined from three-component local waveforms recorded by IRIS-DMC and Geofon broadband IA networks. The epicentral distances of all stations were less than 10°. Moment tensor solutions of the events was performed, simultaneously with the determination of the centroid position. Joint analysis of the hypocenter position, centroid position and nodal planes of the vents indicated the Sumatra fault planes. The hypocenters of all four events clearly prefer that strikes parallel to Sumatra Island to be the fault plane in all cases. Regional moment tensor solutions of this paper along with the focal mechanisms, which represent the only double couple of moment tensor, is plotted. The MT solutions consist of all events have strike slip one fault type. The preferable seismotectonic interpretation is that the events activated Sumatra fault zone at a depth of about 14-18 km, corresponding to the interplate of Sumatra fault boundary.