Aftershocks seen after 6.5 temblor rocks Mati

AFTERSHOCKS are expected to continue, on a lesser frequency and extent, from the magnitude 6.5 weekend earthquake off Davao Oriental’s capital city of Mati, seismologists said.

“We don’t expect future aftershocks to be as frequent and intense as what these were immediately after the earthquake,” said Julius Galdiano, science research analyst at the Philippine Institute of Volcanology and Seismology (Phivolcs).

He noted frequency and magnitude of the aftershocks will decrease over time until these events stop when below-ground geologic conditions leading to the earthquake stabilize.

Phivolcs chief Renato Solidum himself said “There was no report of damage yet but since the quake was offshore... we expect no significant damage,” adding “[there is] no tsunami threat related to the quake.” 

In its preliminary impact assessment, the US Geological Survey also said there was a low likelihood of casualties and damage from the tremor, which had a depth of 62 kilometers.

The Philippines sits on the Pacific “belt of fire” where tectonic plates collide and magnitude 6 tremors are common.

The Hawaii-based Pacific Tsunami Warning Center said there was no tsunami threat from the strong quake.

“It’s unclear when the aftershocks will stop, however,” Galdiano said. Aftershocks are tremors that follow the main shock of an earthquake.

As of noon Saturday, Phivolcs already recorded a series of aftershocks following the 6:53 a.m. earthquake, with the initial aftershock at 7:45 a.m. reaching magnitude 4.9. 

Galdiano said Phivolcs afterwards recorded aftershocks of lesser intensity of the quake which was tectonic in origin, meaning it was caused by the movement of the earth’s crust.

Latest available data also show the earthquake struck 51 km. south 38 degrees east of Mati at a depth of 38 km., Phivolcs noted.

“We consider that earthquake a strong one,” said Phivolcs science research specialist Gail Rivera, noting earthquakes can still strike there in the future.

According to Phivolcs, different areas felt Saturday’s earthquake at varying intensities.

Phivolcs said fresh data show Mati and Baganga in Davao Oriental; Davao City as well as Tagum City and Island Garden City of Samal in Davao del Norte reported the earthquake at intensity 5.

General Santos City; Alabel, Glan and Malapatan in Sarangani; Polomolok in South Cotabato; Butuan City, Governor Generoso and Cateel in Davao Oriental; Digos City in Davao del Sur; Jose Abad Santos in Davao Occidental; Braulio Dujali in Davao del Norte and Talacogon in Agusan del Sur reported intensity 4, Phivolcs noted.

Areas that reported experiencing the earthquake at intensity 3 were Tupi in South Cotabato; Cagayan de Oro City; Gingoog in Misamis Oriental; Malaybalay,Valencia, Maramag, Don Carlos, Quezon and Monolo Fortich in Bukidnon; Boston in Davao Oriental; Bagumbayan in Sultan Kudarat and Kiblawan in Davao del Sur, Phivolcs continued.

Phivolcs also said Kidapawan City and Makilala in North Cotabato reported intensity 2.

Based on Phivolcs’ gauge, intensities 5, 4, 3 and 2 indicate an earthquake experienced as strong, moderately strong, weak and slightly felt, respectively.

At intensity 5, Phivolcs said earthquakes are generally felt by most people indoors and outdoors.

Phivolcs said intensity 4 quakes are felt generally by people indoors and by some people outdoors.

Intensity 3 earthquakes are felt by many people indoors, especially in upper floors of buildings, Phivolcs continued.

Few people at rest indoors feel earthquakes at intensity 2, Phivolcs added. With PNA and AFP wires