Proof Of Ground Displacement Seen In West Valley Fault Line
By CHITO A. CHAVEZ
March 5, 2012
MANILA, Philippines — A joint trenching activity recently conducted by the Quezon City government and the Philippine Institute of Volcanology and Seismology (Phivolcs) across the West Valley Fault Line in Barangay Bagong Silangan produced evidence of ground displacement including abrupt change of sediment layers.
The tests also revealed that the exposed trench walls indicated that at least two to three earthquakes had taken place in the area.
Tadeo Palma, secretary to the mayor, said the trenching activity was conducted to identify and determine traces of the fault line like ground rupture movements and slip rate estimates across the fault line.
The activity involved the excavation of two trenches, about 50 meters apart, within the 50-hectare property owned by Banco Filipino in Barangay Bagong Silangan, which, according to the report of the Metro Manila Earthquake Impact Reduction Study (MMEIRS), registered a high susceptibility to earthquakes along with Barangay Payatas in Quezon City.
The Phivolcs is now in the process of collecting charcoal pieces for carbon-14 analysis to determine the approximate time of the occurrence of the earthquakes and the estimate of the age of the sediment layers affected by the ground displacement.
Elmo San Diego, chief of the city’s Department of Public Order and Safety (DPOS), said the MMEIRS study disclosed that a magnitude 7.2 earthquake may originate at the West Valley Fault Line.
“The Phivolcs findings just validated the claim that the West Valley Fault Line is indeed active,†said San Diego, who is also the action officer of the Quezon City Disaster Risk Reduction Management Council.
San Diego reiterated Mayor Herbert Bautista’s call to declare as danger zone the seven-kilometer stretch of the fault system that runs through the city’s periphery.
“The safety of our residents, particularly those living on top of the fault line, is non-negotiable. The fault line is unlivable,†San Diego said.
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