519 aftershocks logged after magnitude 6.8 quake in Surigao del Sur

A closeup of a seismograph machine needle drawing a red line on graph paper depicting seismic and earthquake activity on isolated white background. INQUIRER FILES/STOCK PHOTO

MANILA, Philippines — The Philippine Institute of Volcanology and Seismology (Phivolcs) said more than 500 aftershocks have been logged since Monday’s magnitude 6.8 earthquake off Cagwait town in Surigao del Sur.

As of 7:00 a.m. on Tuesday, 519 aftershocks ranging from magnitude 1.8 to 5.7 were recorded, but only two were felt by residents, according to Phivolcs.

The strongest magnitude 5.7 aftershock occurred at 8:34 a.m. some 44 kilometers (km) northeast of Cagwait Municipality. This tectonic aftershock has a shallow depth of focus of 10 km which Phivolcs believed will unlikely cause damage.

READ: Latest in a series: Magnitude 6.8 quake strikes again off Surigao del Sur

The aftershock was felt in Bayabas, Surigao del Sur at Intensity IV (moderately strong) while Phivolcs’ scales measured it at Instrumental Intensity II (slightly felt) in Tandag, Surigao del Norte and Instrumental Intensity I (scarcely perceptible) in Cabadbaran, Agusan del Norte.

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Phivolcs said the tectonic quake struck 63 kilometers east-southeast of Cagwait at 3:49 a.m. on Monday. The tremor had a shallow depth of focus of one kilometer,

State seismologists said the Philippine trench triggered this temblor which happened less than two days after a powerful 7.4 earthquake that hit waters near Hinatuan town also in Surigao del Sur.