On surviving the next major earthquake

It began with a barely perceptible hum that a few seconds later grew into a gentle shaking that had residents rising to their feet and rushing outside.

The magnitude 6.2 earthquake that occurred at 8:54 PM of April 4, 2023, on Holy Tuesday, did not cause damage but a tsunami warning led to the preemptive evacuation of nine families of Biong, Gigmoto.

Aside from temblor and its nine (9) aftershocks probably encouraging many among the religious Catandunganons to pray harder for deliverance, the temblor unfortunately generated that familiar product of social media: fake news.

An alleged video of the quake’s damage on the San Pedro Calungsod Mission Church at Sicmil prompted local authorities to officially deny the report from the irresponsible netizen.

According to the United States Geological Survey (USGS), the quake hit at a shallow depth of 15 km, about 150 kilometers east of Gigmoto.

Shallow earthquakes are felt more strongly than deeper ones as they are closer to the surface, the USGS says.

Had the intensity reached 7.0 or greater, a tsunami would have been generated considering the shallow depth.

The M6.2 earthquake, according to the USGS, released seismic energy equivalent to 30,089 tons of TNT or about 1.9 atomic bombs.

It is likely that today’s generation would be amazed by this tidbit but those who were “born yesterday” would remember stronger earthquakes.

Historical records show that since 1900, Catanduanes has been hit by 177 earthquakes between magnitude 5 and 6, 23 between magnitude 6 and 7, and eight (8) above magnitude 7.

And of the eight M7+ temblors, two occurred in the last 31 years.

At 6:10 AM, January 11, 1982, a magnitude 7.1 quake struck about four kilometers off Gigmoto but fortunately the epicenter was 45 kilometers deep, causing only strong shaking.

Six years later, on February 24, 1988, a magnitude 7.3 temblor about 39 kilometers ESE of Cabugao, Bato, generated very strong shaking in nearby towns.

While the M7.1 quake released an estimated seismic energy equivalent to 42 atomic bombs, the M7.3 unleashed double that, 84 atomic bombs or about 13 million tons of dynamite.

We are fortunate that none of the M7+ quakes resulted in a tsunami inundating Virac and other coastal towns although there are people still alive who recall an incident decades ago of the sea retreating and coming back to shore after an earthquake.

Catanduanes lies just 200 kilometers west of the Pacific Trench, a major earthquake generator where movement of the earth’s crustal plates is believed to have caused the magnitude 6.2 quake of April 4.

We can expect that we will continue to experience such quakes now and in the future.

It is not comforting to know that in the past 12 months, 686 earthquakes have occurred near the island, with 562 of them barely perceptible. The other 34 are considered significant earthquakes above magnitude 4.0.

Cognizant of this fact, the Provincial Disaster Risk Reduction and Management Office (PDRRMO) is on the right track in launching the “One System, One Response” scheme among its partner agencies such as the PNP, BFP, PRC and volunteer groups in cases of emergency.

According to the World Bank’s Global Facility for Disaster Reduction and Recovery (GFDRR), earthquake hazard in Catanduanes is classified as “medium,” meaning that there is a 10% chance of potentially damaging earthquake in the island in the next 50 years.

There is no substitute for preparation, in building what the PDRRMO refers to as muscle memory in automatically and correctly responding to a devastating earthquake.

That same serious approach should be taken by the public if they want to survive the next Big One.

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