Volcanologists Found It

A team of state volcanologists has confirmed on Monday night that the newly formed natural unnamed formation represents a previously unknown fault that triggered the magnitude 7.2 earthquake last week.

Residents of Anonang, Bohol told the team that right after the October 15 earthquake ,they noticed a long earthen wall that suddenly appeared in their community, Gma news online reported.

Phivolcs scientist, Dr. Teresita Bacolcol said “When we saw it, eureka! This is it.” Bacolcol led the Phivolcs team on Monday to check out sightings of the lengthy earthen wall, which turned out to be the “face” of a fault that currently does not exist on the active fault map of the Philippines.

“We are 100 percent sure that this is the generator [of the earthquake],” said Bacolcol, citing its proximity to the epicenter near the boundary between Sagbayan and Catigbian towns, Gma news online said.

Reports added the fault had moved six days ago, triggering the terrifying tremor that felled churches, left nearly 200 dead and rendered scores homeless.

Scientist explained the wall, or the face of the fault, is the edge of a large area of land that had been thrust upwards as high as three meters, and stretched as far as the eyes can see, cutting off roads and numerous trails.

The fault line’s direction runs northeast to southwest through this town. “Nahati ang Bohol,” according to Leonila Divinagracia, a barangay kagawad here, observing that a wide swath of the province was now more elevated with a clear demarcation.

Reports said that before Monday, the fault’s location had been a mystery, after the East Bohol Fault near the southern coast had earlier been discounted as the source of the earthquake.

“We thought the fault could be offshore or somewhere in the north of the island,” said Bacolcol.

Scientist said the formation is unique. Although still unnamed, the prominent formation is unique in the annals of the country’s recent geological history.

They said it’s considered a “reverse fault” because of the vertical surface rupture, a sign of the enormous energy packed by last Tuesday’s cataclysm. Less powerful quakes cause land to sink rather than rise, Gma news online said.

Reports said the last great earthquake in the country, in northern Luzon in 1990, was caused by a lateral (side to side) movement of a fault, and did not leave a similarly large mark on the terrain.

Doctor Bacolcol and his team of experts had been looking for the fault’s face for days, narrowing their search to the vast “zone of aftershocks” that stretched from the northwest of the island down to the southern coastal town of Loon, where a centuries-old church was reduced to a heap of rubble, the online news report said.

If they had not found the fault, or if it was a “blind fault” with no surface manifestation, the Phivolcs team would have determined the fault line only by analyzing the pattern of aftershocks, according to a member of the team, adding that “it would have taken a lot longer.”

Following a lead given by a Gma reporter, who had accompanied residents of Inabanga town to the fault on Sunday, Bacolcol and his team spent much of Monday documenting a five-kilometer stretch of the fault, and they were far from finished. They are planning to return on Tuesday to trace the fault wherever it led, which could be the sea, Gma news online reported.

Historical earthquake data around the globe shows that an earthquake of magnitude 7.2 can create a visible fault line as long as 100 kilometers. The scientists’ visit to Anonang gave a measure of relief to residents who didn’t know what to make of the massive change to their land.

“We have been scared. What if there are more faults to come? Should we leave?” asked Felix Caray, barangay captain of Anonang, one of many communities across Bohol where people are sleeping outdoors out of fear.

Reports said Bacolcol’s team assured them that this will be the one and only fault here, and it may be generations before another earthquake occurs. The team also advised not to build any homes within five meters of the fault line.

On Monday night at the Phivolcs station in Tagbilaran, Bacolcol and his team were preparing maps, data and photos of their new discovery for the Phivolcs central office.

“This is the holy grail of active fault mappers,” said Bacolcol, who will submit their findings for a revision of the Philippine fault map. “Naiiyak ang team nang makita nila.” Gma news o line reported.

Source: Gma news online