Earthquake events in Negros Oriental may be due to rising magma

The head of the Physics Department of Silliman University in Dumaguete City strongly believes that the ongoing earthquake events in Valencia, Negros Oriental are not tectonic but rather caused by volcanic activity.

This is contrary to the repeated statements of state-run Philippine Institute of Volcanology and Seismology (Phivolcs) that the series of earthquakes is tectonic in origin and that these can be traced to the fault line from Sibulan town to the southwest of the province.

Professor Francisco Ablong, Jr., in an interview Monday afternoon, disclosed that his initial observations, based on data from Phivolcs, were inclined towards potential volcanic activity in the vicinity of the Cuernos de Negros.

Cuernos de Negros, locally known as Mt. Talinis, was categorized by Phivolcs as a potentially active volcano, although it had not erupted in thousands of years, he said.

The term “potentially active volcano” means that “it is really active only that the activity is not directly observable for now,” Ablong explained.

He further said, “there is that element of possibility that it will erupt but nobody can tell when but there are symptoms or indicators whether or not a volcano will erupt.”

“I am more inclined in saying that validation should be made on some kind of magmatic movement under the base of Cuernos de Negros,” Ablong said.

According to him, the earthquakes observed since January 1 this year and even those earlier occurred at the “base of the volcano” - referring to the areas that were at the foot of Cuernos de Negros.

The Physics professor said he had plotted these earthquakes based on data gathered from Phivolcs, which pointed to possible magma rising from underneath the base of the volcano.

The earthquakes that are happening are concentrated somewhere in the vicinity of Cuernos, and “we cannot consider immediately based on the data that the cause is tectonic because when we say tectonic, before a series of earthquakes, the biggest to happen is the main shock,” Ablong pointed out. “There was no main shock.”

More than 100 earthquakes had already been recorded by Phivolcs in Valencia since January 1st and data showed that there were smaller tremors occurring before the biggest one so far took place on January 27, he said.

A magnitude 4.7 earthquake, which Phivolcs plotted as having a reference point in Dauin, occurred around 6:21 a.m. on that day, but an hour or so before that, about three or four smaller earthquakes were recorded in nearby Valencia.

But there are indications, according to Ablong, of potential volcanic activity at Mt. Talinis, such as magma approaching the surface.

“Everytime it moves, it disturbs surrounding rocks and these will be shaken, thus causing volcanic earthquakes,” the scientist said.

“Magmas are high-pressure materials that will cause disturbance of surrounding rocks underneath,” said Ablong.

He is challenging the Phivolcs to deploy experts with the right instruments to validate the possibility of volcanic activity at Cuernos de Negros.

“Phivolcs should come here, bring instruments, and stay there for a period of weeks in order to do a geophysical survey of the current condition of Cuernos de Negros and its surroundings,” he said.

Ablong is hopeful that Phivolcs will bring the right instruments such as for thermal imaging to probe what is happening underneath the ground and a tilt meter to see whether a portion of Cuernos is already tilting downward or upward.

The Physics professor emphasizes the need for a “scientific and intelligent judgment” of what is the present condition of Cuernos de Negros.

He said there was already a drying up of streams and vegetation within its vicinity, most likely “because of the thermal activity underneath.”

Furthermore, surrounding trees and plants are dying because of increasing temperature, as he showed some photos of a portion of land in the volcano area that have already withered or died.

He discounted the possibility of re-injection of water into the pipelines by the Energy Development Corporation (EDC) which owns and operates the geothermal power plants in Valencia as a possible cause for the earthquakes.

According to him, this is just minimal and shallow and will not be able to generate as many shocks or tremors as recorded by Phivolcs.

Phivolcs also concurred in a previous interview with the observation of Ablong regarding EDC activities at the geothermal power plants in Valencia that these would not be the cause of the series of tremors.

The reactions come as some quarters have raised concerns on social media on whether certain activities in the geothermal fields in Valencia may be related to the earthquakes. Many residents in Valencia and nearby towns are increasingly worried each day as the shocks continue.

Ablong, however, suggested that perhaps, EDC could also help by providing data on the series of earthquakes in that town, noting that the company must have seismic instruments and other equipment to monitor the activity of Mt. Talinis.

He said in the coming days, he and his team would visit Cuernos de Negros’ surroundings, and possibly even go as far as Sta. Catalina town as there was a “good deposit of lava” somewhere beyond Barangay Milagrosa there.

While there was no available data as to when Cuernos de Negros had erupted, Ablong said there was presence of lava deposits, lava rocks, igneous rocks and many other similar materials that showed that the volcano had erupted in the past.

There is no imminent danger of the volcano erupting but Ablong warns that the continuing earthquakes will put the people at risk due to dislodged rocks and boulders and landslides.

He called on the local government units to be on the alert and prepare for any eventuality, highlighting that a volcanic eruption at Cuernos de Negros could be predicted even if it did not happen in this lifetime, while earthquakes could never be foretold.*(Judaline F. Partlow/PNA)