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'New' earthquake fault discovered in Manila?

March 7, 2013 2:47pm

Ridge under Manila
'Ridge' under Manila. Geologist Dr. Kelvin S. Rodolfo on March 7 points to what appears to be a newly-identified "ridge" (indicated by the dotted line) separating Manila into flood-prone subsiding areas (yellow and red) and rising areas (green and blue). Observers are speculating that the ridge may be a heretofore unidentified fault line. Paulo Alcazaren, via Facebook
(Updated 9:48 p.m.) While studying movement patterns in the earth under Metro Manila, geologists have discovered a boundary or "ridge" —a possible fault line— between flood-prone subsiding areas and gradually rising areas in the metro.

However, Phivolcs said that there is no clear evidence of a "new" active fault line in Metro Manila.

On the morning of March 6, landscape architect and urban planner Paulo Alcazaren posted a photo on his Facebook page of Dr. Kelvin S. Rodolfo, Professor Emeritus of the Dept. of Earth & Environmental Sciences at the University of Illinois at Chicago, giving a talk on issues surrounding proposed reclamation efforts in Manila Bay.

Rodolfo's talk touched on a geologic survey map of Manila, which indicated areas that are subsiding —and are therefore prone to floods— as well as other areas of the metro that are gradually rising.

Accidental discovery

However, what caught Alcazaren's and other observers' eyes was that there seemed to be a dividing "ridge" separating these subsiding and rising areas.

"Subsidence on one side leads to greater flood risks, but what could be of greater risk is the presence of not one but two major fault lines in the metro —and the scenario of greater loss of lives in a major earthquake," Alcazaren said in his Facebook post.

"Nasilip nila ito accidentally. Pinag-aaralan nila yung subsidence ng Metro Manila. When they were getting data, the rate of subsidence of the northwest side of the metro was different from the southwest side," Alcazaren further explained in a phone interview.

However, Alcazaren reiterated Rodolfo's call for a more comprehensive investigation into the possible existence of a fault.

"Any remote observation has to be verified on the ground," Alcazaren said.

No cause for panic

In a separate interview, Rodolfo explained that it was the Science and Technology Department’s Project Noah (Nationwide Operational Assessment of Hazard) subsidence study that discovered the fault. Rodolfo is as a consultant for Project NOAH.

“The study was conducted mainly because we have lots of evidence on the ground that large areas of Manila are sinking… [My mentioning of the fault was] a side product of our study of areas of subsidence. It gave us the indication that there may be a fault that [was] previously unrecognized,” he told GMA News.

“Ang maganda sa finding namin, kung fault talaga siya, it was manifested because it is moving very slowly,” Rodolfo said.

He noted that his team at Project NOAH is validating their “initial finding.”

“The most important thing is to verify it on the ground. That, I believe, is happening right now. People from Project NOAH are actually going on the ground looking to see whether there is direct evidence on the ground for the existence of the fault,” he added.

Still, the geologist said that the supposed new discovery should not cause panic the public. “It is not the time to make people worried about something as long as we have not really pinned it down scientifically yet.”

Phivolcs assurance

Meanwhile, Phivolcs director Renato Solidum stressed that there was no "new" active fault line in Metro Manila.

Solidum told GMA News that his agency was aware of Rodolfo's findings, but there was no evidence nor indication of another active fault line in the area.

“We have seen the same… Such kind of interpretation must be carefully evaluated if you want to say its is a fault or not… There are so many possible interpretations [when you see the map]. We have to be very careful,” the Phivolcs director said.

He further explained: “We have not found any statistical significance yet that there is indeed a significance uplifting of one part to another.”

"Ang West Valley fault o Marikina Fault Line ang nag-iisang aktibong fault line sa Metro Manila na may scientific basis," he said.

Still, he noted that the possibilities raised by Rodolfo are healthy within the scientific circle. “No one should stop looking at these things because this is important for disaster preparedness.” — with JP Soriano/DVM/KG, GMA News
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