Wall of rock rises out of the ground in the Philippines: new fault triggered large quake
Residents stand next to a long earthen wall which formed following
the Oct. 15 earthquake in Barangay Anonang in Inabanga, Bohol. Phivolcs
scientists said the wall is the face of a previously unknown fault line
which caused the magnitude 7.2 quake
October 24, 2013 – PHILIPPINES – As
the magnitude 7.2 earthquake ended on Oct. 15, residents of Sitio
Kumayot in Barangay Anonang heard an explosive sound like a thunderclap.
Villagers watched in horrified disbelief as the ground cracked open
and, with smoke and the stench of sulphur spreading, one side started to
rise. The emerging wall of rock and earth missed by a hairline the
toilet of baker Menecia Bautista Aparecio, 43. “We will be living
forever in fear, being so close to the fault line,” said Aparecio, who
fears returning to her home and now bakes her “pan Bisaya” or “pan
kinamot,” a local bread, in the village chapel. The rock face, about
three meters high and two kilometers long, raised fears among villagers
that more cracks would appear on the ground and swallow them up.
Scientists, who may declare a 300-meter permanent danger zone around the
fault, described the appearance of the ground rupture as a “eureka”
moment in their search for what they have long suspected was an active
earthquake fault in the area. Government scientists
said the appearance of the yet unnamed fault, which does not exist on
the country’s map of fault lines, triggered the powerful earthquake in
Central Visayas. “We are 100 percent sure that this is the generator (of
the earthquake),” Teresito Bacolcol
told GMA 7 as he noted that the rock face appeared near the quake’s
epicenter at the boundary of Sagbayan and Catigbian towns. “When we saw
(the fault), eureka! This is it.” Bacolcol led a team from the
Philippine Institute of Volcanology and Seismology (Phivolcs), which
inspected the rock face last Monday. “We recommend that no structures
should be built on top of a fault and within the five-meter buffer zone
on both sides of the fault,”
Phivolcs director Renato Solidum told The STAR. He also urged the local
government of Bohol to revise its land use policy around the fault. -Philstar
Geologists from the Philippine
Institute of Volcanology and Seismology (Phivolcs) found “ground zero”
or the fault that triggered the devastating magnitude 7.2 earthquake.
The discovery on Monday confirmed the existence of a previously unknown
fault in western Bohol. The Oct. 15 earthquake claimed around 200 lives
and caused major infrastructure damage, including Spanish-era churches
in Bohol and Cebu. Immediately after the earthquake, Phivolcs said the
tremor was caused by the movement of the East Bohol Fault. The
epicenter, first reported as Carmen town, was later adjusted to the
general area between Sagbayan and Catigbian towns in north central Bohol
based on the distribution of aftershocks. Geologists found a
5-kilometer surface rupture that extended from barangay Anonang in
Inabanga town to barangay New Anonang in Buenavista town. “That fault
motion caused the earthquake,” Renato Solidum, director of Phivolcs told
ABS-CBN News Channel’s Talkback yesterday morning. The ground rupture
pushed the ground upward from two to three meters, cutting through
mountains, roads and possibly settlement areas. Phivolcs teams are still
studying the extent of the fault line which could extend 100 kilometers
or longer.
Meanwhile, aftershocks recorded by
Phivolcs indicate a general distribution from north Bohol to the
offshores of Dalaguete, Alcoy and Boljoon towns in southern Cebu. The
data was plotted on a map by Jessie Alaivar Floren, a private Geographic
Informatino System expert in Cebu. Aside from structural damage,
residents in southern Cebu towns of Alegria and Badian and Carcar City
have complained that ground water turned to “milo” brown. “The
earthquake may have disturbed the clay-limestone land formations in
these areas, affecting their water table and underground water
channels,” said Jun Lucero, senior geologist of the DENR Mines and
Geosciences Bureau (MGB). Lucero told Cebu Daily News that they are now
checking reports of possible liquefaction in several areas in Cebu and
Bohol. Severe liquefaction could result in the sinking or submersion of
lands, he said. Areas near the river and those reclaimed from the sea
are more prone to liquefaction, Lucero said. Structures in reclaimed
areas, he said, should have stronger foundations and must use materials
that can withstand strong ground shaking and liquefaction. -Inquirer
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