評估高度都市化地區鄰近斷層活動性及其地震潛能的重要性，於近來2010 Mw 7.0海地地震與2010 Mw 8.8智利地震所造成的災害中再度被凸顯出來。為了闡明位於菲律賓馬尼拉地區中，由West Marikina Valley Fault（WMVF）與East Marikina Valley Fault（EMVF）所組成的斷層系統Marikina Valley Fault System（MVFS）現今的地殼變形模式及地震潛能，本研究於2008年4月在MVFS地區架設6台雙頻與4台單頻GPS連續監測站來監測MVFS之活動性。各站之座標與速度場採用GAMIT/GLOBK軟體求解。塊體模型結果指出，WMVF斷層滑移速率為10.6 mm/yr，滑移虧損速率為1.9 mm/yr，且WMVF中北段主要呈現鎖定的狀態；GPS速度剖面與NW–SE方向0.7–1.3 μstrain/yr的擠壓應變率更指出WMVF為一帶有壓縮分量的左移斷層。在WMVF南段，應變速率以NW–SE方向約4 μstrain/yr的伸張應變為主；此區域靠近Laguna De Bay之GPS座標時間序列分析顯示，在乾季2008/12–2009/05與2009/12–2010/03時出現累積約19.1與17.5 mm的沉陷量，在濕季時則停止沈陷，甚至在2009年9月26日Ketsana颱風帶來單日250 mm豪雨後，發生20天累積抬升約14 mm的情形，此時間序列的週期變化推測與季節性地下水補注量的變化有關。此外，WMVF南段兩側測站東西方向基線長度在濕季2008/06–2008/11與2009/06–2009/11時產生5.9與11.8 mm/yr的伸長，推測可能因為降雨或地下水位變化導致地層間的孔隙水壓力增加，使得有效應力降低而促使WMVF南段發生潛移。塊體模擬結果指出EMVF北段呈現鎖定的狀態，中段則呈現出微量右移型態，移動速率約2.1 mm/yr。最大可發生地震規模Mw 6.75與WMVF滑移速率虧損量6.2 mm/yr指示出地震復發週期可能為293年。

Recently, 2010 Mw 7.0 Haïti earthquake and Mw 8.8 Chile earthquake re–emphasize the importance to evaluate earthquake potential and the fault activity near highly urbanized areas. In order to understand the recent deformation mode and earthquake potential of the Marikina Valley Fault System (MVFS) which includes West Marikina Valley Fault (WMVF) and East Marikina Valley Fault (EMVF), we set up 6 dual–frequency and 4 single–frequency continuous GPS stations in April, 2008 to monitor the activity of MVFS. In terms of GPS analysis, we used GAMIT/GLOBK 10.35 software to obtain the coordinate and velocity of the stations. The block model indicates that the slip rate is 10.6 mm/yr; slip rate deficit is 1.9 mm/yr and the middle northern part of WMVF is locked; GPS velocity profile and the GPS–derived strain rate: 0.7–1.3 μstrain/yr contraction with NW–SE direction shows WMVF is a left–lateral strike–slip fault with a component of compression. In terms of southern part of WMVF, strain rate is about 4 μstrain/yr extension strain with NW–SE direction; GPS coordinate time series indicates that the GPS stations in the region near Laguna De Bay accumulated 19.1 and17.5 mm subsidence during dry season: 2008/12–2009/05 and 2009/12–2010/03 but stop subsidence in wet season. Even after the 250 mm torrential rain which was brought by the Ketsana typhoon on September 26, 2009, the area uplifted 14 mm in the next 20 days. We speculated that the GPS time series cycles have something to do with the change of seasonal groundwater recharge. Furthermore, the baseline time series among the GPS stations located nearby the southern part of WMVF had 5.9 and 11.8 mm/yr extension in wet season: 2008/06–2008/11 and 2009/06–2009/11, we infer that is because rainfall or groundwater level change increases the stratum’s pore water pressure and decreases the effective stress then to trigger creeping in the southern part of WMVF. The block model also indicates that the northern part of EMVF is locked, and the middle part of EMVF is right–lateral with a slight rate of 2.1 mm/yr. The slip rate deficit on WMVF is 6.2 mm/yr, which gives the maximum credible earthquake of Mw 6.75 and the recurrence period of 293 years.

Alvir, A. D., A geological study of the Angat–Novaliches region, Philippine J. Sci., 40, no. 3, 359–419, 1929.
Arcilla, C. A., Geology and mineral resources of the Montalban Quadrangle, Luzon Philippines, Philippine Council for Agricultural and Resources Research Development, National Institute of Geological Sciences, unpublished report, 188, 1983.
Barrier, E., P. Huchon, and M. Aurelio, Philippine Fault: a key for Philippine kinematics, Geology, 19, 32–35, 1991.
Beutler, G., A. Geiger, M. Rothacher, S. Schaer, D. Schneider, and A. Wiget, Dreidimensionales Testnetz Turtmann 1985–1993, Teil II (GPS–Netz), Geodätisch–geophysikalische Arbeiten in der Schweiz, 51, 1995.
Daligdig, J. A., R. S. Punongbayan, G. M. Besana, and N. M. Tungol, The Marikina Valley Fault System: Active Faulting in Eastern Metro Manila, PHIVOLCS Professional Paper, 01, 1–20, 1997.
Deguchi, T., Y. Kinugasa, and M. Omura, Observation of Creep on Valley Fault System in Republic of the Philippines by InSAR and leveling survey, Japan Geoscience Union Meeting 2007.
Dong, D., T. A. Herring, and R. W. King, Estimating regional deformation from a combination of space and terrestrial geodetic data, J. Geodesy, 72, 200–214, 1998.
Encarnación, J., Multiple ophiolite generation preserved in the northern Philippines and the growth of an island arc complex, Tectonophysics, 392, 103–130, 2004.
Encarnación, J. P., S. B. Mukasa, and E. C. Obille. Jr., Zircon U–Pb geochronology of the Zambales and Angat ophiolites, Luzon, Philippines: Evidence for and Eocene arc–back arc pair, J. Geophys. Res., 98, 19991–20004, 1993.
Estey, L. H., and C. M. Meertens, TEQC: The multi–purpose toolkit for GPS/GLONASS data, GPS Solutions, 3, no. 1, 42–49, 1999.
Feigl, K. L., D. C. Agnew, Y. Bock, D. Dong, A. Donnellan, B. H. Hager, T. A. Herring, D. D. Jackson, T. H. Jordan, R. W. King, S. Larsen, K. M. Larson, M. H. Murray, Z. G. Shen, and F. H. Webb, Space geodetic measurement of crustal deformation in Central and Southern California, 1984–1992, J. Geophys. Res., 98, 21677–21712, 1993.
Fitch, T. J., Plate convergence, transcurrent faults, and internal deformation adjacent to southeast Asia and the west Pacific, J. Geophys. Res., 77, 4432–4460, 1972.
Galgana, G., M. Hamburger, R. McCaffrey, E. Corpuz, and Q. Chen, Analysis of crustal deformation in Luzon, Philippines using geodetic observations and earthquake focal mechanisms, Tectonophysics, 432, 63–87, 2007.
Gervasio, F. C., The geology, structures and landscape development of Manila and suburbs, Philippine Geologist, 22, 178–192, 1968.
Haman, B. Z., On Sustainability of Withdrawal from Metro Manila Groundwater System and Availability of Additional Groundwater Resources, UNDP, 1997.
Hanks, T. C., and H. Kanamori, A moment–magnitude scale. J. Geophys. Res., 84, 2348–2350, 1979.
Herring, T. A., J. L. Davis, and I. I. Shapiro, Geodesy by radio astronomy: the application of Kalman filtering to very long baseline interferometry, J. Geophys. Res., 95, 12561–12581, 1990.
Irving, E. M., Geomorphological implications of the Marikina drainage pattern, Rizal Province, Luzon, P.I., Philippine Geologist, 1, no. 2, 1–4, 1947.
King, R. W. and Y. Bock, Documentation for the MIT GPS analysis software: GAMIT, version 9.6, Mass. Inst. of Technol, Cambridge, 1997.
Liu, Z., W. Zhan, Y. Yao, M. Zhan and D. Zhang, Kinematics of convergence and deformation in Luzon Island and adjacent sea areas: 2–D finite–element simulation, Journal of Earth Science, 20, no. 1, 107–116, 2009.
McCaffrey, R., Crustal block rotations and plate coupling, in Plate Boundary Zones, Geodynamics Series 30, S. Stein and J. Freymueller, editors, AGU, 101–122, 2002.
Nelson, A. R., S. F. Personius, R. E. Rimando, R. S. Punongbayan, N. Tungol, H. Mirabueno and A. Rasdas, Multiple large earthquakes in the past 1500 years on a fault in Metropolitan Manila, the Philippines, Bull. Seismol. Soc. Am., 90, 73–85, 2000.
Oca, G. R., and J. F. Potenciano, Geology and foundation problems of the projected Marikina Arch Dam, Journal of the Geological Society of the Philippines, 17, no. 4, 119–137, 1963.
Okada, Y., Surface deformation due to shear and tensile faults in a half–space, Bull. Seism. Soc. Am., 75, 1135–1154, 1985.
Prescott, W. H., J. C. Savage, and W. T. Kinoshita, Strain accumulation rates in the western United States between 1970 and 1978, J. Geophys. Res., 84, 5423–5436, 1979.
Quiazon, H., Groundwater Situation in Manila and Suburbs. Bureau of Mines. Manila Philippines, 1971.
Repetti, W. C., Catalog of Philippine earthquakes, Bull. Seismol. Soc. Am., 36, 133–322, 1946.
Rimando, R. E., and P. L. K. Knuepfer, Neotectonics of the Marikina Valley fault system (MVFS) and tectonic framework of structures in northern and central Luzon, Philippines, Tectonophysics, 415, 17–38, 2006.
Rimando, R. E., R. S. Punongbayan, R. Macaspac, and L. Tansinsin, Creeping Fault Segment of the West Marikina Valley Fault in Muntinlupa–San–Pedro–Biñan Area, Philippine Institute of Volcanology and Seismology Internal Report, 1996.
Roca, R. Jr., Current Conditions and Development Plan of the Groundwater System in Metro Manila. Paper presented at the Regional Workshop on Management Modelling for Conjunctive Water Use, 1993.
Sagiya, T., S. Miyazaki, and T. Tada, Continuous GPS array and present–day crustal deformation of Japan, PAGEOPH, 157, 2303–2322, 2000.
Satirapod, C., C. Rizons, and J. Wang, GPS single point positioning with SA off: How accurate can we get? Survey Review, 36, no. 282, 255–262, 2001.
Seno, T., S. Stein, and A. E. Gripp, A model for the motion of the Philippine Sea Plate consistent with NUVEL–1 and geological data, J. Geophys. Res., 98, 17941–17948, 1993.
Shen, Z. K., D. D. Jackson, and B. X. Ge, Crustal deformation across and beyond the Los Angeles basin from geodetic measurements, J. Geophys. Res., 101, 27957–27980, 1996.
Spilker, J., GPS signal structure and performance characteristics, J. Inst. Navi., 25, 121–146, 1978.
Terzaghi, von K., The shearing resistance of saturated soils and the angle between the planes of shear, First Int. Conf. Soil Mech., 1, 54–56, 1936.
Thibault, C., GPS Measurements of crustal deformation in the northern Philippine Island arc. Master’s Thesis, Department of Geological Sciences, Indiana University, Bloomington, Indiana, 1999.
Wells, D. E., N. Back, D. Delikaraoglou, A. Kleusberg, E. J. Krakiwsky, G. Lachapelle, R. B. Langley, M. Nakiboglu, K. P. Schwarz, J. Tranquilla, and P. Vanicek, Guide to GPS Positioning, Canadian GPS Associates Fredericton, New Brunswick, Canada, 1986.
Wells, D. L., and K. J. Coppersmith, New empirical relationships among magnitude, rupture length, rupture width, rupture area, and surface displacement, Bull. Seismol. Soc. Am., 84, no. 4, 974–1002, 1994.
Willis, B., Geologic observations in the Philippine Archipelago, Bulletin of the National Research Council of the Philippine Islands, 13, 1–54, 1937.
Yumul, G. P. Jr., C. B. Dimalanta, R. A. Tamayo Jr., and R. C. Maury, Collision, subduction and accretion events in the Philippines: A synthesis, The Island Arc, 12, 77–91, 2003.