Quake faults at Fort can rupture fuel lines?

PREMATURE: Interior Secretary Mar Roxas better be careful not to give the impression that he is already rendering judgment on what or who was behind the explosion at Two Serendra condominium that killed three persons in Taguig City last May 31.

Roxas was reported yesterday as clearing Ayala Land, project developer, of any responsibility. Was he misquoted?

Assigning legal responsibility, or determining guilt or innocence, should be left to the courts.

Even assuming Roxas has evidence of what caused the explosion, he might want to step back and ask: Which scenario (a bomb, gas leak, or whatever) will serve better the business interests of his friends at Ayala Land?

He should be careful not to be seen as advancing the blast theory that is most favorable to the Ayalas.

*   *   *

OTHER ANGLES: There was a theory that gas had leaked and built up in the destroyed Serendra Unit 501-B because the piping may have been altered. But the owner, Marianne Cayton-Castillo, affirmed that they never touched the piping system.

A university geoscience professor injected another technical angle to the investigation by reviving talk about Fort Bonifacio, site of Serendra, sitting on a web of earthquake faults that could move any time and crack fuel lines.

It is true that there are active faults running through Taguig, the site of the former military camp that Ayala Land bought from First Pacific after the latter found it too expensive after winning it in bidding in 1995.

While there is no clear link yet between the Serendra blast and the presence of fault lines, it may be useful to review this physical aspect of the general area.

*   *   *

FAULT ZONE/LINE: Sometimes people talk of fault lines when they are referring to a fault zone, and vice versa.

The valley created in Marikina when the land sank is a “fault zone” or a “fault system.” The sinking left at its periphery “fault lines” or “ruptures” or “cracks,” specifically in the east and in the west of the valley

As local officials, we were told, did not relish being associated with calamities, the city’s name was dropped. Now these active structures are simply called the Valley Fault System, the East Valley Fault Line and the West Valley Fault Line without mentioning Marikina.

The mapping of the still-active Valley Fault Zone/System and the fault lines that pass through Fort Bonifacio and contiguous densely populated areas should be continued and hazard maps updated.

*   *   *

FAULT MAPS: In the map that we have seen, the East fault line starts from San Rafael, Montalban, to Pasig City, while the West fault runs from northeast of Montalban, vanishes when it reaches Fort Bonifacio, then resumes its way to the Tagaytay volcanic ridge in Cavite.

Technicians explained that some fault lines were not detected in some Fort Bonifacio sections in the map, because much of the then military camp was restricted area.

Maps are based partly on aerial surveys of the National Mapping and Resource Information Authority, the older they are the more useful. Geologists and surveyors also scour the land for telltale signs such as ruptures, slides and unusual movements in the soil and rocks.

In really detailed studies, geologists dig up areas to gain more accurate measurements. But trenching costs a lot and requires considerable time. It can also delay development.

*   *   *

SIGNS ERASED: One problem is that some areas in Fort Bonfacio were bulldozed and cleared prematurely. This erased physical indications of faults, ground ruptures and such tectonic phenomena.

Buyers may want to check technical maps or secure certifications before buying. Or if they had bought a parcel already, they can still go to the maps for a more judicious location of their buildings.

We have learned, by the way, that an updated map is being prepared.

We have also been assured that reputable developers have made sure they first checked the maps and other geological data from technical sources.

*   *   *

CHECK MAPS: Property buyers at the Fort and pricey villages outside may find it useful to verify if the land they want to purchase or where they intend to build sits on or near a fault.

There are maps in the website (www.phivolcs.dost.gov) of the Philippine Institute of Volcanology and Seismology.

Those who want to be sure can bring their land titles to Phivolcs, where detailed checking can be done using the parcel’s boundary set forth in the titles. If we are not mistaken, the institute issues certifications.

The late Phivolcs Director Raymundo Punongbayan once told us that while it is dangerous to construct a house or building on top of a fault, locating it just a few meters off can reduce or eliminate the risks with proper engineering.

He cited quake-hit places in Japan that he had visited and documented. He showed his pictures of structures remaining intact just five meters away from a fault that had moved.

*   *   *

‘MODERNIZATION’: The P8-billion raised from the sale of Fort Bonifacio in 1955, as well as the proceeds of other privatized camps, were to go to modernizing the armed forces. (Pardon the term “modernization” which appears to be an inappropriate reference to mere upgrading.)

In 1996, the two chambers of the Congress approved a joint resolution giving full support to RA 7898, the AFP Modernization Act.

It was during the term of then President Fidel V. Ramos that a consortium led by First Pacific became the development partner of the Bases Conversion Development Authority for Fort Bonifacio.

*   *   *

RESEARCH: Access past POSTSCRIPTs at www.manilamail.com. Follow us via Twitter.com/@FDPascual. Send feedback to [email protected]