Aseismic Movement of the Western Valley (Marikina) Fault

Kinugasa Yoshihiro¹, Deguchi Tomonori², Kurita Katsumi³, Omura Makoto⁴,
Papiona L. Kathleen^1, ⁵, Rimando E. Rolly⁵

¹ Tokyo Institute of Technology
² Nittetsu Mining Consultants Co., Ltd.
³ Tokyo Metropolitan Collage of Industrial Technology
⁴ Kochi Women’s University
⁵ Philippine Institute Volcano logy and Seismology

Abstract

Continuous movement of the Muntinlupa segment of the Western Valley Fault (also known as the Marikina Fault) has been monitored by repeated survey. Since there has been no horizontal slip noticed, the survey method follows a simple leveling survey method using an electronic digital level and bar-code leveling staff. Overall accuracy is estimated to be 2-3 mm. Survey intervals were once in every three month at the beginning, started in September 1999, and now once in every half a year.

Until the survey done in December 2007, six survey lines out of nine show continuous vertical dislocation of the fault (Figure 1). Other three survey lines show no additional dislocations even though an echelon cracks on the pavement are still visible. Trace of each fault is not changing its location throughout the survey period. The width of the deformation zone associated with each strand of the fault is very limited ranging from 1.5 to 6.1 meters.

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