MANILA — Surigao del Norte may further experience aftershocks equal to or greater than this week’s magnitude 4.8 temblor arising from the magnitude 6.7 earthquake that rocked some parts of the province last month.
“Such aftershocks are still possible there so people must prepare accordingly,” said science research assistant Bhenz Rodriguez from State-run Philippine Institute of Volcanology and Seismology (Phivolcs).
A magnitude 4.8 temblor of tectonic origin struck Tuesday night (March 14) at 11 kms south 43° west of Surigao del Norte’s San Francisco municipality, said Phivolcs.
Phivolcs noted the temblor was reported felt at intensity V in San Francisco and Surigao City; intensity IV in Mainit, Malimono and intensity III in Alegria.
The moderately strong temblor was also reported felt at intensity II in Southern Leyte’s San Ricardo, Dinagat’s San Jose and Agusan del Norte’s Kitcharao.
“That temblor was another aftershock of the magnitude 6.7 earthquake off Surigao last month,” said Rodriguez.
Citing latest available data, Phivolcs reported 302 aftershocks from such earthquake as of 8 a.m. Monday (March 13).
Forty-two of those aftershocks were felt, Phivolcs noted.
According to US Geological Survey (USGS), aftershocks are smaller earthquakes that occur in the same general area during the period following a larger earthquake.
USGS noted aftershocks represent minor geological re-adjustments along portion of the fault that slipped at the time of the earthquake.
Philippine authorities said the February 2017 Surigao earthquake’s strongest aftershock so far — a magnitude 5.9 temblor earlier this month — damaged 83 houses in the province.
Reports also said an elderly person died of cardiac arrest after that aftershock while another person sustained injuries from a wall’s collapse from that seismic event.
Aftershocks occur as underground rocks disturbed during earthquakes move while settling into place, noted Phivolcs science research specialist Mylene Enriquez.
She noted such rocks differ in movement during settling.
“That’s why an earthquake’s aftershocks aren’t always of the same magnitude,” she added. Catherine Teves/PNA-northboundasia.com