Phivolcs records an astounding 900 aftershocks in first 24 hours after 6.9 magnitude earthquake
February 7, 2012 – PHILIPPINES – The local seismology monitors recorded as much as 900 mild aftershocks as of noontime today after the 6.9-magnitude earthquake hit Central Visayas on Feb. 6. According to the local Philippine Volcanology and Seismology (Phivolcs), through Engineer Nolan Evangelista, aftershocks are just ordinary incidents after a major earth movement. Evangelista also shared that the most noticeable aftershocks reached intensity 3 that was recorded at around 6:10 p.m. yesterday and another one at 7:32 p.m., which reached intensity 2. “There have been numerous aftershocks but most of them were so mild, Boholanos did not seem to notice them. Since these are aftershocks, these are never stronger than the major earthquake, unless another movement is caused by another or a similar fault,” Evangelista added. He also explained that the Phivolcs has earlier issued intensity reference charts. These charts help ordinary people measure the intensity of the earthquake while looking at the objects shaken by the tremor.
On the other hand, a magnitude scale usually issued by the Phivolcs uses the equipment recorded data which are available in their office. It means that a magnitude scale reading is a more accurate measurement of the tremor than an intensity scale which can be subjective of one’s personal experience, he said. Surviving with reports of very mild damages in cracked buildings, Bohol has also shuddered at the tremors that came after. Over this, school authorities have suspended classes in kindergarten to secondary levels so building officials and Department of Education (DepEd) authorities can inspect the integrity of school structures. Dr. Lorna Rances, schools division superintendent, urged local and school officials to help assess the damages in school buildings in their areas of responsibility and subsequently issue certifications of safe occupancy of school buildings to DepEd so that classes can resume. Yesterday, some residents felt worried when text messages about an impending tsunami circulated, after a Phivolcs-issued tsunami warning number 2. Engineer Evangelista explained that Phivolcs tsunami alert 2 means that there is a certainty that meter high waves do come and that residents in coastal areas are advised to move away from the 20-meter zones from the sea levels for their safety. It means there is a real possibility that water may rise a meter high, but in yesterday’s case, it should have come to Bohol an hour after the major quake, he said. –PIA.gov
