The local seismology monitors recorded as much as 900 mild aftershocks as of noontime yesterday after the 6.9-magnitude earthquake struck the Visayas area and northern Mindanao before noontime last Monday.
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. Monday 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.
Provincial Schools Division Superintendent Lorna Rances asked the parents to understand the sudden advisory on suspension of classes shortly after the notice on resumption of classes aired early morning yesterday.
Rances explained that the advisory from Department of Education regional office to suspend the classes in all levels—from pre-school to high school only came at 7:15 a.m.
This is to give the teachers, principals and school supervisors time to inspect all classrooms for cracks.
Rances said the regional director just wants to make sure that the incident in Negros Oriental will not be repeated wherein everybody was watching on high-rise buildings, but the classroom that collapsed was a one-storey building.
She sought the assistance of Governor Edgar Chatto and all the mayors to fast-track the inspection on all schools in the province.
In the DepEd-7 directive, classes will only resume when school officials already secure a certification from engineers that the classrooms are already safe for holding classes after the assessment.
For their part, the governor and the mayors already directed all the barangay officials to help in checking the classrooms.
Chatto explained that the assistance of barangay officials is necessary because it would take time for the municipal engineer–one in every town—to go around all the buildings in all the schools in the barangays.
Each barangay has a carpenter who can help assess and it would be faster this way because there is only one school in every barangay.
Even if the governor already confirmed that the province is already safe, Rances said it is best to implement precautionary measures because earthquakes come in surprise.
Administrative Officer Ruel Namocatcat of the City Schools Division expressed confidence that they could finish the inspection of all the classrooms in 16 elementary schools and six high schools in Tagbilaran in one day, having TLE (Technology and Livelihood Education) teachers, and Industrial Arts teachers who helped engineers and carpenters.
Based on initial assessment made right after the quake, cracks are evident on the walls of the TLE building, toilet of the 3rd year high school building, Science Building near the stairway, and the toilet of SPA building in Dr. Cecilio Putong National High School.
Minor cracks had already been noticed in the new Bagong Lipunan buildings in Tagbilaran City East School, and Ubujan Elementary School.
Evangelista 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.
On this, school authorities suspended classes in kindergarten to secondary levels so building officials and Department of Education (DepEd) authorities can inspect the integrity of school structures.
Some residents grew anxious after the text messages about an impending tsunami circulated, after a Phivolcs-issued tsunami warning number 2.
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 Monday’s case, it should have come to Bohol an hour after the major quake, he said.
He informed that Bohol can only be vulnerable to tsunami if Western Negros fault is the source, and he added that it can only happen when the quake generates a magnitude 7.
In that case, Tagbilaran City and some southern Bohol towns can be affected by meter-high waves.(with reports from PIA-Bohol)
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