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.
-  A. M. Dziewonski, T.-A. Chou, and J. H. Woodhouse, “Determination of earthquake source parameters from waveform data for studies of global and regional seismicity,” J. Geophys. Res., Vol.86, pp. 2825-2852, 1981.
-  G. Ekström, M. Nettles, and A. M. Dziewonski, “The global CMT project 2004-2010: Centroid-moment tensors for 13,017 earthquakes,” Phys. Earth Planet. Inter., 200-201, pp. 1-9, 2012.
-  H. Kawakatsu, “Automated near-realtime CMT inversion,” Geophys. Res. Lett., Vol.22, pp. 2569-2572, 1995.
-  H. Kawakatsu, “On the realtime monitoring of the long-period seismic wave field,” Bull. Earthq. Res. Inst., Vol.73, pp. 267-274, 1998.
-  E. Fukuyama, M. Ishida, D. S. Dreger, and H. Kawai, “Automated seismic moment tensor determination by using on-line broadband seismic waveforms,” ZISIN, Vol.51, pp. 149-156, 1998 (in Japanese with English abstract).
-  D. Dreger and D. V. Helmberger, “Determination of source parameters at regional distances with three-component sparse network data,” J. Geophys. Res., Vol.98, pp. 8107-8125, 1993.
-  D. Dreger, R. Uhrhammer, M. Pasyanos, J. Franck, and B. Romanowicz, “Regional and far-regional earthquake locations and source parameters using sparse broadband networks: a test on the Ridgecrest sequence,” Bull. Seism. Soc. Am., Vol.88, pp. 1353-1362, 1998.
-  M. E. Pasyanos, D. S. Dreger, and B. Romanowicz, “Toward realtime estimation of regional moment tensors,” Bull. Seism. Soc. Am., Vol.86, pp. 1255-1269, 1996.
-  F. Tajima, C. Megnin, D. S. Dreger, and B. Romanowicz, “Feasibility of real-time broadband waveform inversion for simultaneous moment tensor and centroid location determination,” Bull. Seism. Soc. Am., Vol.92, pp. 739-750, 2002.
-  L. Scognamiglio, E. Tinti, and A. Michelini, “Real-Time Determination of Seismic Moment Tensor for the Italian Region,” Bull. Seism. Soc. Am., Vol.99, No.4, pp. 2223-2242, 2009.
-  A. Kubo, E. Fukuyama, H. Kawai, and K. Nonomura, “NEID seismic moment tensor catalogue for regional earthquakes around Japan: quality test and application,” Tectonophysics, Vol.356, pp. 23-48, 2002.
-  J. Ristau, “Implementation of Routine Regional Moment Tensor Analysis in New Zealand,” Seismol. Res. Lett., Vol.79, No.3, pp. 400-415, 2008.
-  M. Nakano, T. Yamashina, H. Kumagai, H. Inoue, and Sunarjo, “Centroid moment tensor catalogue of Indonesia,” Phys. Earth Planet. Inter., Vol.183, pp. 456-467, 2010.
-  M. Nakano, H. Kumagai, and H. Inoue, “Waveform inversion in the frequency domain for the simultaneous determination of an earthquake source mechanism and moment function,” Geophys. J. Int., Vol.173, pp. 1000-1011, 2008.
-  B. J. T. Punongbayan, H. Kumagai, N. Pulido, J. D. Bonita, M. Nakano, T. Yamashina, Y. Maeda, H. Inoue, A. A. Melosantos, M. F. Figueroa, P. C. M. Alcones, K. V. C. Soriano, I. C. Narag, and R. U. Solidum, Jr., “Development and Operation of a Regional Moment Tensor Analysis System in the Philippines: Contributions to the Understanding of Recent Damaging Earthquakes,” Journal of Disaster Research, Vol.10, No.1, 2015 (this number).
-  A. A. Melosantos, K. V. C. Soriano, P. C. M. Alcones, J. U. Pantig, J. D. Bonita, I. C. Narag, H. Kumagai, and H. Inoue, “Performance of Broadband Seismic Network of the Philippines,” Journal of Disaster Research, Vol.10, No.1, 2015 (this number).
-  B. L. N. Kennet, E. R. Engdahl, and R. Buland, “Constraints on seismic velocities in the Earth from travel times,” Geophys. J. Int., Vol.122, pp. 108-124, 1995.
-  M. Bouchon, “Discrete wave number representation of elastic wave fields in three-space dimensions,” J. Geophys. Res., Vol.84, pp. 3609-3614, 1979.
-  Y. Y. Kagan, “3-D rotation of double-couple earthquake sources,” Geophys. J. Int., Vol.106, pp. 709-716, 1991.
-  Y. Y. Kagan, “Simplified algorithms for calculating double-couple rotation,” Geophys. J. Int., Vol.171, pp. 411-418, 2007.
-  Y. Okada, K. Kasahara, H. Sadaki, K. Obara, Shoji, S. Sekiguchi, H. Fujiwara, and A. Yamamoto, “Recent progress of seismic observation networks in Japan – HI-net, F-net, K-NET and KiK-net –,” Earth Planets Space, Vol.56, No.8, pp. xv-xxviii, 2004.
-  Scilab Enterprises, “Scilab: Free and Open Source software for numerical computation (Windows, Version 5.4.1) [Software],” 2012,
available from: http://www.scilab.org [accessed January 11, 2014]
-  P. Wessel , W. H. F. Smith, R. Scharroo, J. F. Luis, and F. Wobbe, “Generic Mapping Tools: Improved version released,” EOS Trans. AGU, Vol.94, pp. 409-410, 2013.