The Philippine Institute of Volcanology and Seismology (Phivolcs) 7 said it did not make a mistake in issuing a tsunami alert level 2, after the 6.9 magnitude earthquake occurred in Negros and Cebu at 11:49 a.m. last Monday.

Rolando Montañez of the Phivolcs Seismic Monitoring Station in Lapu-Lapu City said in a radio dyRC interview that the warning was intended for towns along the western coast of Cebu Province, facing Negros.

“Wa mi masayop, sakto to amo (We did not make a mistake), said Montañez.

Tsunami alert level 2 means there could be meter-high waves and people are advised to stay away from the shore, according to the Philippine Information Agency.

The advisory caused many people in downtown Cebu City and Mandaue to panic around mid-afternoon yesterday, even though Phivolcs had lifted the alert status.

Montañez said if a high magnitude earthquake occurs, this should already serve as warning of a possible tsunami.But he stressed that people should remain calm and should verify any information they receive.

According to the US National Oceanic and Atmospheric Administration (NOAA), which also monitors the Pacific Ocean, a tsunami can happen minutes after an earthquake that occurs in the Pacific Ocean.

The Pacific Ocean, the biggest body of water in the world, is surrounded by a series of mountain chains, deep ocean trenches and island arcs, sometimes called the “ring of fire. The size of the Pacific and the large earthquakes associated with the “ring of fire combine to produce deadly tsunamis, read a NOAA brochure on tsunamis.

Tsunamis are likely to occur following an earthquake that originates from the ocean floor or closer to the shore. Tsunamis may also occur when underwater volcanoes erupt.

Residents in Cebu and Negros can expect aftershocks in the next few weeks, said Montañez. He said 775 aftershocks have been recorded as of 7:45 a.m. yesterday. Thirty of these aftershocks occurred yesterday.

Montañez said that, so far, the strongest aftershock occurred at 7 p.m. last Monday with a 4.0 magnitude.

Montañez said no volcanic activity was recorded following the magnitude 6.9 earthquake that struck Cebu and Negros last Monday.

Based on Phivolcs’s earthquake bulletin, last Monday’s quake was the strongest this year.

There was a 6.5 magnitude quake recorded in 1905 in Negros Occidental, near Bantayan Island and Silay (Negros Occidental).

In 1922, a 6.3 magnitude quake occurred between Bohol and Cebu, which was also felt in Negros and Leyte.

Saul Gonzales, Department of Energy (DOE) energy industry management division chief, assured yesterday that power supply in the Visayas grid is back to normal.

Power plants in the Visayas tripped or shut down automatically when last Monday’s earthquake occurred.

Gonzales said power was restored around 1 p.m. of the same day. He assured that supply was stable yesterday and there were no scheduled power outages.

Mae Katherine Melchor, corporate communications office of Cebu Energy Development Corp. (CEDC), said CEDC’s two coal-fired power plants generated a full load with a total of 144 megawatts.

Melchor said, though, that CEDC’s subsidiary, Panay Energy Development Corp. (PEDC), scheduled its Unit 2 for preventive maintenance.

Elmer Cruz of the National Grid Corp. of the Philippines (NGCP) said there were no major damages in transmission facilities as a result of the quake.

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