Surigao residents should expect more aftershocks following the magnitude 6.7 quake that shook the city on Friday, the director of a national institute warned.
University of the Philippines (UP) National Institute of Geological Sciences (NIGS) Director Mario Aurelio, who compared the quake to the 2012 Negros Oriental tremor, said these aftershocks may be felt in the next months.
"In 2012, we experienced aftershocks even two months, three months after the main shock. It can last for a year, but they wane in terms of magnitude," he said in an interview with "[email protected]" on Monday.
"The same will be expected with this earthquake. We can expect for the next two or three months still aftershocks, but as I said, nature says that the magnitudes will be getting smaller and smaller," he added.
Aurelio explained that the recent quake was caused by the Philippine fault, located within the vicinity of Northern Surigao. Movements by this "fracture," he said, have been recorded as early as 1800s.
A segment of a fault line moves as a way for the crust of the earth to "release the energy that has accumulated for many, many years," according to Aurelio.
Hence, having released the energy, he said that "portion of the fault should not be expected to move again soon--I'm not saying never, but soon."
However, because the Philippine fault is long, and only a portion of it released the energy, this energy "goes to the other segments of the fault."
"In theory again, the more likely to move next would be those areas which has not had earthquakes in the recent past," he said.
Aurelio also explained that this recent movement of the fault was a lateral movement, and would not cause large tsunamis, which happen when there is a "significant vertical movement in the sea bed."
"In this case, it's horizontal. So this kind of earthquake does not generate a large tsunami. It can cause little disturbance on the sea level, but it's not a destructive tsunami," he said.