This article was accepted into the corpus but its outbound wikilinks were never NER-processed — typical at the deepest BFS hop or when the run's entity cap was reached. No expansion funnel to show.
| West Marikina Fault | |
|---|---|
| Name | West Marikina Fault |
| Location | Rizal, Metro Manila, Philippines |
| Length km | 25 |
| Type | Strike-slip fault |
| Plate | Philippine Sea Plate, Sunda Plate |
| Status | Active |
| Last event | 1658 (estimated) |
West Marikina Fault The West Marikina Fault is an active right-lateral strike-slip fault system in the eastern sector of Metro Manila and adjacent Rizal province in the Philippines, forming a principal crustal structure that influences seismic hazard in Luzon. It lies within a complex tectonic setting that includes the Philippine Trench, Manila Trench, and the Philippine Fault Zone and interacts with regional structures such as the Marikina Valley and Sierra Madre foothills. The fault has been the focus of geological, geodetic, and engineering studies because of its proximity to densely populated areas including Manila, Pasig, Antipolo, and Cainta.
The West Marikina Fault is mapped as a northwest-southeast trending strike-slip structure extending roughly along the Marikina Valley corridor, bisecting urban and peri-urban municipalities such as Marikina, Pasig, Antipolo, and Cainta. Geologists and seismologists from institutions like the Philippine Institute of Volcanology and Seismology and universities such as the University of the Philippines Diliman and Ateneo de Manila University have characterized the fault through field mapping, trenching, and seismic reflection studies. Its activity is evaluated alongside other Philippine structures including the Philippine Fault Zone, the Digdig Fault, and the Makati Fault when assessing metropolitan seismic risk.
The fault lies in the Luzon geologic domain where interaction between the Philippine Sea Plate and the Eurasian Plate (Sunda Plate segment) produces transpressional and transtensional deformation. Regional tectonics involve the nearby subduction zones: the Manila Trench to the west and the Philippine Trench to the east, and the broader arc systems like the Sunda Arc and the Philippine Mobile Belt. Basement lithologies adjacent to the fault include sequences of the Sierra Madre Group and upper Cenozoic basin deposits of the Marikina Formation, with Quaternary alluvium in the Marikina Valley. Structural relationships connect the West Marikina Fault with splays and transfer faults that link to the San Mateo Fault and other segments within the Philippine Fault System.
Field mapping and geophysical surveys indicate the West Marikina Fault comprises multiple strands with varying continuity and segmentation; major segments are identified beneath fluvial terraces and uplifted blocks near the foothills of the Sierra Madre Mountains. The fault exhibits right-lateral strike-slip motion with local oblique dip-slip components, interfacing with basins such as the Laguna de Bay catchment and geomorphic features like river offsets in the Marikina River channel. Detailed segmentation studies reference geomorphology, trench exposures, and seismic reflection lines used by researchers from Geological Society of the Philippines and international collaborators from institutions like United States Geological Survey and Japan International Cooperation Agency.
Paleoseismic trenching and historical catalogs attribute large late Holocene earthquakes to structures in the Marikina Valley region, with some studies estimating a major event around the 17th century and recurrent surface-rupturing events on millennial to centennial timescales. Instrumental seismicity recorded by networks operated by PHIVOLCS and regional observatories such as the Institute of Volcanology and Seismology archives document microseismic activity and triggered events that illuminate strain accumulation. Earthquake scenarios consider interactions with major ruptures on the Philippine Trench and intra-Luzon thrusts such as the Mishima Fault-style analogs; paleoseismology teams from Tokyo University and National University of Singapore have contributed comparative analyses.
Hazard assessments integrate fault parameters—slip rate, recurrence interval, maximum credible magnitude—with urban exposure data from agencies including the National Disaster Risk Reduction and Management Council and metropolitan planners from Metro Manila Development Authority. Estimated maximum magnitudes for plausible ruptures inform building-code revisions by the Department of Public Works and Highways and retrofitting priorities for lifelines such as bridges on Marikina–Infanta Highway corridors, water supply networks, and power substations serving Quezon City and central business districts like Ortigas Center. Risk mitigation measures emphasize land-use zoning, seismic-resistant design per national standards, emergency response planning with Philippine Red Cross and municipal disaster offices, and community outreach in barangays across affected municipalities.
Continuous monitoring employs seismic networks run by PHIVOLCS, GPS campaigns conducted by universities including UP Diliman Institute of Geological Sciences, and InSAR studies using satellites from programs like Sentinel and missions coordinated by agencies such as Japan Aerospace Exploration Agency. Research priorities encompass constraining slip rates, detecting creep or locked behavior, refining paleoearthquake chronologies via radiocarbon dating in trenches, and 3D seismic hazard modeling with international cooperation from groups including USGS and regional partners in the ASEAN science community. Peer-reviewed outputs appear in journals and conference proceedings of organizations like the Seismological Society of America and the International Association for Seismology and Physics of the Earth’s Interior.
Proximity of the fault to dense urban fabric places hospitals, schools, transport corridors, and high-rise developments at seismic risk; infrastructure assessments guide resilience investments for utilities managed by entities such as Manila Water Company, Maynilad Water Services, and power distribution firms serving Metro Manila. Urban planners in the Department of Human Settlements and Urban Development and local governments incorporate hazard maps into zoning ordinances, evacuation routes, and emergency shelter siting, while engineering firms and academic centers develop retrofit strategies for structures in Ortigas Center, Bonifacio Global City, and peri-urban districts near the Marikina watershed. Continued integration of geological data into spatial planning is central to reducing societal impacts from potential future ruptures.
Category:Geology of Rizal Category:Seismic faults of the Philippines