Study Seismotectonic and Its Potential as a Precursor Regional Level in Northern Sumatra Earthquake
Abstract
Earthquake activity varies spatially and temporally. Seismologists are trying to accurately describe the seismicity using statistical models and based on these make predictions of future seismicity. Two basic laws, the Gutenberg Richter law that describes the earthquake size distribution of earthquakes, and the Omori law that describes the decay of aftershock activity are helpful in characterizing the independent and dependent part of the seismicity, respectively. Prediction of earthquakes, however, is currently impossible (Nuannin, 2006).
Simeulue earthquake of 11 April 2012, 15:38 WIB with magnitude 8.5 SR (BMKG), is a matter that is not suspected by scientists, whereas the earthquake occurred on the oceanic intraplate of Indo-Australian Plate with a large magnitude to the shear fracture patterns.
Seismotectonic parameter analysis using data from the earthquake catalog BMKG and National Earthquake Information Center (NEIC), from January 1th 1973 to April 10th 2011, with a border of 0°N - 6°N and 93°E - 99°E, which covers an area of Northern Sumatra. From the analysis using analysis software ZMAP (Wiemer, 2002) obtained a b-value variation ranged from 0.7 - 1.7, the variation values ranged from 5-10 whereas a time recurrence earthquake with magnitude 6.8 in general is between 5-40 years. Large earthquakes during the period 2004 - 2011 occurred in the region indicated by the relatively low seismotectonic parameter. A low b-value anomaly, around the Mw=9, (2004), Mw=8.7, (2005), and Mw=8.5, (2012) events supports the hypothesis that rupture will occur in high stress (low b) areas.
Keywords: Frequency-magnitude distribution, aftershocks, Omori law, seismicity, earthquake prediction.
