Abstract:
The Sumatra subduction zone, one of the most active plate tectonic margins in the world,
is characterised by the Indo-Australia Plate subducting beneath the Sunda plate and Andaman
micro plate, causing seismic activity along the plate boundary. There had been five major
earthquakes of magnitude greater than 8.0 in this region from 2004 to 2014. Three of them are
dip-slip and rest of the two is strike-slip type events. Regional earthquake activity after the
occurrence of those five events was analyzed.
Hypocentral data obtained from the Data Management Center at the Incorporated
Research Institutions for Seismology for the period from January 2000 to December 2014 of
magnitude 3.0 were used for the analysis. A statistical analysis was carried out to know whether
earthquake activity has increased after the major five events and the analysis was carried out
both qualitatively and quantitatively. The results of the analysis show that the number of
earthquakes in the region has increased considerably after the occurrence of April, 2012
magnitude 8.6 and 8.2 strike-slip events. Further results show that there is no change in the
regional earthquake activity after the occurrence of other three major dip-slip type events.
Present study results reasonably agree with the results obtained by the other studies carried out
with different methods.
In the context of Sri Lanka, strike-slip type focal mechanism of the 2012 two major
events may be the reason for increasing of activity in the region, especially in Eastern part of
Sri Lanka near Maduruoya, Highland-Wijayan boundary and Wadinagala area of Ampara
District.
