Reports of ‘minor cracks, eroded soil’ follow swarm of quakes in Cam Sur

GUINOBATAN, Albay — Local government units in Camarines Sur province have reported damage to infrastructures following the swarm of earthquakes that have been rocking the province since last week, a report from the Office of Civil Defense (OCD) Bicol said Monday.

The OCD Bicol said three Camarines Sur towns have reported minor cracks in government-owned establishments and eroded soil under a footbridge.

Last October 14, the Philippine Institute of Volcanology and Seismology (Phivolcs) recorded a 4.3 magnitude quake at 10:08 p.m.

It was followed by a 4.2 magnitude quake on Friday, October 15, at 1:20 a.m.

Two days later, on Sunday afternoon, another 4.2 magnitude quake rocked the province.

As of Monday night, Phivolcs has recorded 27 earthquakes of varying magnitudes since last week. The epicenter of the quakes was in Canaman town.

Paul Alanis, a resident volcanologist at the Phivolcs in Legazpi City, said in a phone interview Monday that these are considered earthquake swarms instead of aftershocks because the general trend of the magnitudes does not decrease.

“These swarms have different magnitudes. As you can notice, we recorded 4.3, then there’s 2.5, then there’s another one with magnitude 3 and 4,” he said.

The weakest of the felt quakes was recorded the following day at 2:33 a.m. It was a magnitude 2 quake.

In Pili, Camarines Sur’s capital town, multiple cracks were observed in the regional Department of Agriculture office.

The Pili Sports Complex’s support steel bars were also dislocated.

Meanwhile, the provincial road in Bagong Sirang village was also damaged.

An enlarged hole was also seen in the middle of La Purisima Bridge in La Purisima village.

Authorities have also noticed that the soil under a footbridge in San Jose village was eroded.

In Minalabac town, cracks were seen in the evacuation center, mayor’s office, the municipal agriculturist’s office, the treasurer’s office, and the Municipal Trial Court. The assessor’s office’s ceilings were also damaged.

In Calabanga town, cracks were also seen on the walls of the town council’s office, the municipal hall, and the agriculturist’s office.

No estimate on the cost of damage was provided in the OCD report.

Alanis said that Bicol folks must learn how to live with the earthquakes because the entire country is tectonically active.

“After the 1990 Luzon Earthquake, the Structural Code of the Philippines was already fixed, so if there are old structures, they are already retrofitted,” Alanis told Inquirer.

“That’s just one aspect. Another one is the residents’ houses? Do they have hazard maps? Do they know where to go? Do they have contingency plans?”

He also said that residents do not need to worry about the earthquake being connected to Mount Isarog.

“The quakes are tectonic in origin, meaning their movements are related to the fault,” he said. “And based on our instruments’ assessment on Isarog, there are no signs that the volcano is having abnormal activities.”

Mount Isarog is listed by Phivolcs as an active volcano. Its last known eruption was in 3,500 BCE (before common era) or over 5,500 years ago.