By Ellalyn De Vera-Ruiz
The moderately strong 5.9-magnitude earthquake that jolted Surigao del Norte last Friday causes close to 2,000 lesser-sized tremors within 72 hours.
According to Philippine Institute of Volcanology and Seismology (Phivolcs) science research analyst John Lery Deximo, as of 8 a.m. last Monday, 1,968 aftershocks have been recorded close to the original source of the 5.9-magnitude earthquake last Feb. 8.
It ranged between 1.4 and 5.1 magnitudes.
However, he pointed out that only 22 tremors, including the strongest aftershock measuring 5.1-magnitude last Feb. 10, were felt.
Deximo explained that the earthquakes occurred at shallow depths and can be attributed to the movement of an unnamed local fault in the vicinity of Surigao del Norte.
He warned the public that aftershocks, mostly with smaller magnitudes, may persist for the next three to six months.
Phivolcs noted that Eastern Mindanao, including Surigao del Norte and Davao Occidental, is one of the seismically active areas in the country because of the Philippine Fault and Philippine Trench, which are the main earthquake generators that can affect the area.
In addition, there are other local faults which can be sources of small- to large-magnitude earthquakes.
On the average, around 20 earthquakes daily are recorded by Phivolcs all over the country. Earthquakes are frequent in the Philippines because of several active faults surrounding or crisscrossing the country.
Phivolcs record earthquakes almost every day but some of them are too weak to be felt.