SORSOGON CITY: Bicol Region could expect more tremors in the coming days as various fault zones that traverse the region have become more active, a senior official of the Philippine Institute of Volcanology and Seismology (Phivolcs) said.
In a phone interview with Media Solutions, Eduardo Laguerta, senior resident volcanologist of PhiVolcs in Legazpi City, said the fault zones were activated by the recent strong quakes that jolted Bicol and Samar.
Laguerta pointed out that Bicol is sandwiched by two quake zones, the Philippine Fault located near Masbate and the Philippine Trench in the Pacific area off Catanduanes.
These areas could be potential sources of strong earthquakes of magnitude 8 that could generate local tsunami especially if it comes from shallow origin, he said.
Recently, the Phivolcs signed a memorandum of understanding (MoU) with some government agencies and a mining company in Bicol for the establishment of a Tsunami Early Warning System (TEWS).
Laguerta, however, explained that an earthquake could only be potentially destructive if it has a high magnitude and comes from a shallow source of up to maximum 20 kilometers as faults can generate earthquakes of up to 70 kilometers in depth.
Some of the destructive quakes that hit Bicol in recent memory were in 1954 which hit Sorsogon and in Ragay, Camarines Sur in 1973 which also generated a tsunami.
The volcanologist said the quake last March in Masbate originated from the Philippine Fault and so did the most recent quake that was traced in Samar which registered at Magnitude 7.6.
According to the United States Geological Service (USGS), “magnitude and intensity measure different characteristics of earthquakes. Magnitude measures the energy released at the source of the earthquake and is determined by measurements on seismographs.
Intensity, on the other hand, measures the strength of shaking produced by the earthquake at a certain location. Intensity is determined from effects on people, human structures, and the natural environment.”
Laguerta, however, said that tremors are to be normally expected as the Philippines sits on the Pacific Ring of Fire where numerous volcanoes are located in the Pacific Basin considered as area of strong earthquakes.
Bicol alone has sixteen volcanoes, three of which are active - Mayon in Albay, Bulusan in Sorsogon, and Asog in Iriga City, while three are potentially active – Mt Labo in Camarines Norte, Isarog in Camarines Sur, and Malinao in Albay -- while the other 10 are all inactive.
But volcanoes do not cause strong earthquakes that could be potentially destructive, most are not felt by humans, he said.
Laguerta said the presence of these volcanoes attest to the geological setting of Bicol which also contributes to the occurrence of earthquakes although volcanic quakes are hardly felt by humans and are only recorded by seismograph. – By Media Solutions/