Phivolcs: Dec. 7 tremor magnitude 5.4 not 6.4

By Cet Dematera


The immediate announcement of the Philippine Institute of Volcanology and Seismology (Phivolcs) followed by a text blast from the National Disaster and Risk Reduction Management (NDRRMC) saying that the 10:37 PM Dec. 7 (Monday) earthquake has a magnitude of 6.4 has created panic among several residents with some even scampered for their safety and ran out of their houses.


Minutes after the earthquake, the Phivolcs website stated that the quake was measured at magnitude 6.4 and said it is “expecting aftershocks.”


Then at 10:42 PM, the NDRRMC sent a text message to cell phone users stating: “Magnitude 6.4 lindol naganap sa Prieto Diaz, Sorsogon. Aftershocks ay inaasahan.” (6.4 magnitude earthquake took place in Prieto Diaz, Sorsogon. Aftershocks are expected.)


At 12:09 AM, Dec. 8, Phivolcs changed its announcement about the magnitude of the tremor from 6.4 to 5.4. Its post was also mistakenly timed as “12:09 PM.” instead of 12:09 AM.


The error in the announcement of the eathquake’s magnitude had irked residents who panicked, while dozens of netizens had posted their varied reactions in the social media.


Rositte Roxas, 24, said that she briskly walked from their second floor outside of their house while the tremor was going on.


“It was so strong that we see the hanging frames in our walls oscillating. We were gripped in fears that we all ran out of the house from the second floor and stayed outside for several minutes,” said Roxas, a resident of Bonot, a coastal village in Legazpi City, where intensity 4 was recorded.


Jemalyn Arcilla, 30, a mother of three, said that she was so nervous that she and her children just hid under their table.


“I was so afraid that I did not think anymore of going out of the house because we are at the first floor and the second floor is concrete. Something could have happened to us if the earthquake lasted longer,” Arcilla, a resident of an exclusive subdivision in Legazpi City said.


Paul Alanis, Phivolcs chief in Bicol, explained that the magnitude 6.4 strength of the earthquake was the first computation produced by their instruments.


Alanis said that the magnitude 6.4 was contained in their first earthquake information bulletin, then was revised in their second bulletin to 5.4, when more data had already arrived at their monitoring system.


“But when almost 70 of out of 100 monitoring stations had already sent data, it was already revised to 5.4 instead of earlier reported 6.4,” Alanis told Bicol Mail.


The 5.4 magnitude temblor occurred at 10:37 PM and traced 37 kilometers north of Prieto Diaz, Sorsogon with depth of 77 kilometers.


Intensity 5 was felt in Sorsogon City; intensity 4 in Legazpi City; Virac, Catanduanes; Naga City; and Catarman, Northern Samar;

Intensity 3 in Bulusan, and Irosin, Sorsogon; Catbalogan City, Sipocot, Camarines Sur; Borongan City, Eastern Samar; and Palo, Leyte; intensity 2 in Naval, Biliran; and Jose Panganiban, Camarines Norte; and, intensity 1 in Lopez, Quezon; and Casiguran, Aurora.


Raden Dimaano, chief of the Sorsogon Provincial Disaster Risk Reduction and Management Council (PDRRMO), said that they did not receive any reported casualty or significant damage to property until press time.


“Our local disaster officials confirmed that they did not receive reports of any casualty. No unusual changes in the condition of the coastal waters are noted. Thanks God,” Dimaano told Bicol Mail.