Palawan safest, no earthquake faults - INQUIRER.net, Philippine News for Filipinos

Palawan safest, no earthquake faults - INQUIRER.net, Philippine News for Filipinos

By Alcuin Papa
Philippine Daily Inquirer
First Posted 23:50:00 01/16/2010

Filed Under: Earthquake


APART from the profusion of spectacular landscapes and seascapes that has made it the favorite of many travelers, it would seem that the paradise island of Palawan also offers the safest haven for those fearful of a Haiti-like tremor occurring in the country.

Compared to other parts of the Philippines, Palawan is “relatively stable” geologically, according to Mahar Lagmay, a professor of the University of the Philippines National Institute of Geological Sciences (UP-NIGS).

“There are hardly any earthquakes in Palawan and certainly none strong enough to cause major damage. The whole island is probably the most stable area of land in the country,” Lagmay said.

An expert on earthquake faults, Lagmay has constructed a map of earthquake epicenters which he plotted using information from the United States Geological Survey (USGS) from 1929 to 2009.

Lagmay said there were hardly any active faults under the island compared to the rest of the country. (A fault or fault line is a fracture in the rock within the earth’s crust that is the causal location of most earthquakes.)

Continental, not oceanic, rock

While Palawan does have fault lines, these are “old” and experts are still debating whether these fault lines are active or not, Lagmay said.

For instance, there is an ongoing and heated debate on whether the Ulugan Bay fault near the famed Palawan Underground River is active, Lagmay said.

Lagmay believes Palawan is stable largely because the island was once part of continental Asia which separated around 100 million years ago and drifted toward the Philippines.

“The rock of the island is continental and different from other parts of the country, which is made of oceanic rock,” he said.

Hence, the crust of the island is thicker at 30 kilometers, compared to the oceanic rock’s 12 km, having derived from the Pacific seabed.

“The crust of the island is thicker and older and, therefore, not as prone to earthquakes,” said Lagmay.

No major faults

The island is also not bordered by any major trench or fault line, he said.

“The South China Sea area is more stable tectonically. Combined with the continental material, there is little chance for the development of active faults in Palawan,” he said.

Also, the movement of the ground in the South China Sea is not as fast as the eastern side of Luzon, which is moving toward the Asian mainland at the rate of 7 centimeters a year, and the eastern side of Mindanao, which is moving toward the Asian mainland at 10 cm a year.

“Because of the slow movement, there is no compression of forces in the island,” Lagmay said.

On the other hand, large parts of the Philippine archipelago are sandwiched between two trenches, the Manila Trench in the west and the Philippine Trench in the east.

“Movements in these trenches generate stress in the faults. That is why there are so many earthquakes in the mainland [Philippines],” he said.

“If you ask me where I would build a house in the country, I’d say Palawan,” he said.