Recording of local earthquakes in Simeulue

Abstract

From December 12, 2005 to March 22, 2006 we operated a temporary network of 8 stations (Guralp CMG-6T short-period 3-component stations) on Simeulue island as part of the seismological network of the SEACAUSE experiment. Seismic noise was dominated by surf on the south coast and cultural noise on the north coast and inland stations. For location, the data from this network were combined with the GITEWS/SEACAUSE ocean bottom network. Typically 7-8 locatable events are registered per day but this rate increases dramatically after several events with magnitudes larger than 5.5 within the array. Events occur on or near the plate interface, in the overriding plate and probably in the downgoing plate. The largest concentration of events is found just south of Simeulue island and its extension along strike, near the presumed updip limit of the co-seismic rupture. These events define a nearly horizontal plane and activity exhibits strong alongstrike variability. Deeper events define a plane with a dip of approximately 15 degrees, presumably the top of the downgoing plate. The data from this network are archived at SeisUK and the IRIS-DMC with network code ZB (valid for years 2005-06).