PHIVOLCS: Damaged structures in Itbayat may have used porous limestone

Marje Pelayo   •   July 31, 2019   •   1148

Photo by Dominic de Sagon Asa

MANILA, Philippines – The municipality of Itbayat and other island towns in the province of Batanes in Northern Luzon are landmasses that emerged from the ocean, according to the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

The area’s soil composition manifests its origin, according to Science and Technology USec. Renato Solidum.

“Doon sa Itbayat ang makikita mong mas maraming bato doon ay limestone (You notice in Itbayat, most of the stones there are limestone),” the PHIVOLCS Director said.

“Ang limestones ay galing sa corals na namuhay sa ilalim ng tubig. Kaya lang napapaangat ito dahil sa pagkilos ng fault, (Limestones are formed from corals on the sea bed. They surface to the ground when the fault moves),” he added.

In July 27, a series of three moderately strong earthquakes rocked the municipality of Itbayat – magnitudes 5.4, 5.9 and 5.8, respectively.

It was in 2015 when Itbayat experienced its latest intensity 5 tremor.

But after 60 or 70 years, it was only on Saturday (July 27) that intensity 6 was again experienced in the area.

According to Solidum, most of the houses or structures suffered damages because the materials used in their constructions were mostly limestone.

Though limestone-based structures could stand strong tropical cyclones, they couldn’t hold strong against earthquakes.

Also, some structures had no steel frames that supposedly add strength and resilience.

“Dahil ang limestone ay madaling matunaw o naaagnas habang tumatagal dahil sa ulan, nagiging marupok ang limestone, (Limestone is a porous material and easily absorbs liquid when drenched in rainwater. Limestone easily breaks),” Usec. Solidum explained.

Limestone was also traced in old churches that were destroyed during a magnitude 7.2 earthquake that struck the province of Bohol in 2013.

Other structures that were damaged also showed traces of limestone that’s why they were not able to stand the strength of the tremors. – (MNP with reports from Rey Pelayo)

Magnitude 5.1 quake rattles Occidental Mindoro

Robie de Guzman   •   December 21, 2021

A magnitude 5.1 quake jolted parts of Occidental Mindoro and nearby areas on Tuesday, the Philippine Institute of Seismology and Volcanology (PHIVOLCS) said.

In a bulletin, PHIVOLCS said the epicenter of the quake was located 15 kilometers northeast of Sablayan, Occidental Mindoro. It occurred at 12:08 p.m.

The temblor was a tectonic in origin and had a depth of 15 kilometers.

PHIVOLCS said the quake was felt at the following areas:

• Intensity IV – Sablayan and Rizal, Occidental Mindoro
• Intensity III – Abra De Ilog, Santa Cruz and Calintaan, Occidental Mindoro; Calapan City and Bansud, Oriental Mindoro
• Intensity II – Makati City; Batangas City; Baco, Oriental Mindoro
• Intensity I – Puerto Galera, Oriental Mindoro; Tingloy, Batangas;

“This is an aftershock of the October 03, 2021 M5.3 Sablayan, Occidental Mindoro Earthquake event,” the agency noted in its report.

Damage and aftershocks are to be expected following the quake, PHIVOLCS said.

Magnitude 5.5 quake hits Paluan, Occidental Mindoro — Phivolcs

Maris Federez   •   December 13, 2021

MANILA, Philippines — A magnitude 5.5 earthquake hit the town of Paluan in Occidental Mindoro at 5:12 in the afternoon on Monday (December 13).

The Philippine Institute of Volcanology and Seismology (Phivolcs) said the tremor was tectonic in origin with a depth of 104 kilometers.

Reported intensities were as follows:

Intensity IV- Calatagan, Batangas; Puerto Galera, Oriental Mindoro;

Intensity III – Batangas City, Lemery, Malvar and Bauan, Batangas; Tagaytay City and Amadeo, Cavite; Quezon City; City of Manila and Pasay City

Intensity II- Taguig City; Mandaluyong City; Makati City; Caloocan City; Malabon City; Tanay, Rizal; San Felipe, Zambales

Instrumental Intensities, on the other hand, reported the following:

Intensity IV – Calatagan, Batangas; Calapan City, Oriental Mindoro

Intensity III – Tagaytay City, Cavite; Plaridel, Bulacan; Batangas City; San Jose, Occidental Mindoro

Intensity II – San Ildefonso, Calumpit, and San Rafael, Bulacan; Carmona, Cavite; Muntinlupa City; Olongapo City; Malolos City, Bulacan; Dolores, Quezon; Talisay, Batangas

Intensity I – Pasig City; Quezon City; Las Piñas City; Malabon City; Marikina City; Guagua, Pampanga; Cabanatuan City, Nueva Ecija; Mulanay and Mauban, Quezon; Pandi and Marilao, Bulacan

Phivolcs said that there was no notable damage from the quake but aftershocks are likely to take place.

PHIVOLCS: Magnitude 5.3. quake jolts Batangas, others areas

Robie de Guzman   •   December 13, 2021

MANILA, Philippines — An earthquake with a magnitude of 5.3 hit parts of Batangas and other nearby areas, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) said Monday.

In its earthquake bulletin, the PHIVOLCS said the quake was recorded approximately 24 kilometers southwest of Calatagan Batangas around 5:12 p.m.

The temblor had a depth of 99 kilometers and was tectonic in origin.

PHIVOLCS said Intensity 3 was felt in Quezon City while intensity 2 was felt in San Felipe in Zambales.

Instrumental Intensity 1 was felt in Quezon City, Tagaytay City, Batangas City, and Calatagan.

PHIVOLCS said no damage is expected from the quake but aftershocks are likely to occur.

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