Regional Moment Tensor Analysis in the Philippines: CMT Solutions in 2012–2013
Jun D. Bonita*, Hiroyuki Kumagai**, and Masaru Nakano***
*Philippine Institute of Volcanology and Seismology (PHIVOLCS), PHIVOLCS Building, C.P. Garcia Avenue, U.P. Campus, Diliman, Quezon City, Philippines
**Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan
***R&D Center for Earthquake and Tsunami, Japan Agency for Marine-Earth Science and Technology (JAMSTEC), Yokohama, Kanagawa 3173-25, Japan
Recently, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) has upgraded its seismic network, equipping it with accelerometers and broadband seismometers for intensity and focal mechanism determinations. As part of this upgrade, PHIVOLCS adapted the use of a source analysis system called SWIFT to determine the centroid moment tensor (SWIFT CMT). SWIFT CMT solutions were estimated for medium to large size earthquakes (4.1 ≤ Mw ≤ 7.6) in the Philippines for the period of January 2012 to November 2013 and were statistically evaluated with respect to the CMT solutions of the Global Centroid Moment Tensor (GCMT) Project. The seismic moments, moment magnitudes, centroid locations, depths and focal mechanisms of most of the SWIFT CMT solutions are found to be consistent to those of the GCMT solutions for earthquakes with Mw ≥ 4.6. The SWIFT system with the new broadband seismographic network provides more CMT solutions for moderate size earthquakes (Mw ≥ 4.1) than GCMT. SWIFT proves to be useful in the development of the Philippines CMT catalogue that will lead to a better understanding of seismotectonics in the Philippines.
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