The Valley Fault System (VFS) Atlas is a handbook that includes large scale maps of the Greater Metro Manila Area (GMMA) showing locations transected by the VFS. The PHIVOLCS FaultFinder, meanwhile, is a web application that displays the VFS as well as all faults transecting the rest of the country. It uses proximity searches to identify nearest active faults from a device’s current position or from a user’s identified area of interest.

Both the VFS Atlas and the PHIVOLCS FaultFinder were designed to give the public accurate information on the location of active faults to mitigate and prepare communities against the dangers of ground rupture. The tools may aid local government units as well as other stakeholders in their land-use planning, risk assessments, disaster management and other activities related to earthquake effects mitigation and preparedness.

Background and Problem

There are about 30 active fault systems in the Philippines from where earthquakes may originate. Two of the most common faults are the Philippine Fault consisting of at least 20 segments distributed from Luzon to Mindanao and the Valley Fault System consisting of two segments transecting the GMMA area. The 7.8-magnitude Luzon Earthquake in 1990, which was caused by the movement along the Philippine Fault (Digdig Segment), resulted in the collapse and damage of buildings and other manmade structures. The total amount of damages reached about USD 0.5 billion (or PhP 15 billion). People killed in the quake were recorded to be at least 1,600; many others were injured and/or missing. Following the Luzon Earthquake, PHIVOLCS increased its efforts to prepare and educate the public on seismic hazards, particularly in areas with high population densities, important infrastructures, and other elements-at-risk. One such high-risk region is GMMA which is transected by the VFS. In Metro Manila, the following key cities are transected by the West Valley Fault (WVF): Marikina, Quezon City, Pasig, Makati, Taguig and Muntinlupa. Movement along the WVF, as a segment of the VFS, may result in a 7.2-magnitude earthquake, which is highly destructive. Consequences of this fault movement may include hazards emerging from ground shaking, liquefaction, earthquake-induced landslides and ground rupture. Ground rupture hazard may be the most difficult to avoid because no engineering interventions have yet been developed to prevent this. Given that ground rupture occurs along active faults, PHIVOLCS has taken all necessary initiatives to accurately map the location of active faults and reflect them on maps to inform the public.

Solution and Impact

The VFS Atlas and the PHIVOLCS FaultFinder were developed to fill in gaps in information between the Institute and the public. The former closely details location of the VFS in GMMA, while the latter provides a quick guide to active fault locations. The public can consequently measure distances of areas with respect to active faults more easily. The FaultFinder also allows stakeholders to choose base maps where the faults may be overlain. The VFS Atlas contains 33 map sheets of varying scales, showing areas transected by the VFS. In 2012, as part of the GMMA Ready Project, the Institute enhanced the VFS, mapping it in detail using very old aerial photographs and plotting the results on the most recent base maps in the areas. The use of 2004-derived 1:5,000 scale planimetric maps, which show relatively recent landscapes and built-up areas, addressed the difficulty in mapping on 1950s 1:50,000 scale topographic maps. The VFS Atlas not only shows location of active faults but also identifies fissures due to groundwater extraction in some portions of Muntinlupa, Cavite and Laguna. PHIVOLCS decided to include these fissures so that communities may distinguish fissures from active faults. The VFS Atlas, being a handbook, makes information readily accessible to stakeholders inquiring about areas along the VFS or adjacent to it.

PHIVOLCS released the FaultFinder, which was developed in collaboration with the Geological Survey of Japan (GSJ), in order to make information dissemination on active faults more efficient. In PHIVOLCS, the term “fault finder” originally referred to active fault mappers. Nowadays, the term has a new meaning. The new “FaultFinder” presents results of geologist’s active fault mapping work by a few taps using a mobile phone or clicks on a computer keyboard. Unlike before when stakeholders find map reading a hurdle to retrieve active faults information, now they can access all of PHIVOLCS’ fault information even without having a skill in map reading. FaultFinder was developed to showcase the location of active faults in the Philippines in one platform. It may be used to measure the shortest distance between an active fault and a user’s current location, which is determined using the gadget’s tracking device, or the shortest distance between an active fault and a specific site, which is identified by a user. Active faults shown in the application are results of various active fault mapping projects conducted by PHIVOLCS or in collaboration with international partners since the 1990s. Map resolution varies depending on the purpose of the maps produced and the availability of references during mapping.


The VFS Atlas was launched in May 18, 2015. Following its launch, a number of PHIVOLCS stakeholders requested for VFS-related assessments. The application has increased awareness and started discussions about earthquakes. The Department of Education even requested PHIVOLCS for lists of schools in GMMA transected by the VFS. Release of the VFS Atlas also triggered fault markings on the ground. As of March 2016, 1,579 of the digital copy of the Atlas was distributed in CDs, while 106,695 were downloaded online. It was also featured in The Summit Express and Rappler and reached 57,536 Facebook users. Requests for ground rupture hazard assessment as well as lectures for earthquakes and earthquake hazards also increased dramatically following the release of the Atlas. For the FaultFinder, the site has more than 170,000 hits since its launch in July 2016 with users from around the world. In the Philippines, majority of its users have searched for information about the Valley Fault System. It also reached at least 21,000 Facebook users.


“Fully appreciated and timely release of Atlas for info dissemination.” – Rick Aquino, User “A very important tool for disaster preparedness, mitigation, and response.” – Riza Baldoria, User “FaultFinder can be used not only by engineers, urban planners, and property developers, but by ordinary citizens as well.” – Rappler “A handy reference.” – GMA News Online