At least 230 aftershocks recorded by Philvolcs after twin Batanes quakes
Published Jul 29, 2019 02:57 pm
By Ellalyn De Vera-Ruiz
Two days after moderately strong quakes hit Batanes province, at least 230 earthquake events of small- to moderate-sized tremors have been recorded by the Philippine Institute of Volcanology and Seismology (Phivolcs).
A resident looks at damaged houses in Itbayat town, Batanes islands on Saturday, July 27, 2019. (AP Photo / Agnes Salengua Nico / MANILA BULLETIN)
According to Phivolcs science research assistant Maila Advincula, the magnitudes 5.4 and 5.9 temblors last Saturday have triggered 230 series of earthquake events, and have been slightly or strongly felt in 11 incidents.
Of the recorded series of earthquakes, 35 were plotted from their original source.
Phivolcs also pointed out that prior to the earthquakes last July 27, earthquakes with magnitudes ranging from 4.2 to 4.8 occurred from July 22 to 26. The maximum reported ground shaking intensity was 4.
It said that these earthquake events could have weakened the buildings and structures prior to the 5.9-magnitude main shock, resulting in greater damage than would have been expected.
Phivolcs reminded the public to be cautious in entering structures visibly weakened or with signs of damage by the earthquake events, as these impacts may further be aggravated by the aftershocks.
In case of houses and other buildings with visible damage, it is recommended to temporarily avoid getting into these structures, and immediately coordinate their inspection by the municipal/city engineering office.
It asked engineers from the local government, other agencies and organizations to inspect buildings and other infrastructures to determine their integrity, and recommend appropriate actions to concerned affected groups or individuals.
Likewise, slopes should be checked for tension/incipient cracks that may have resulted from the strong ground shaking. Tension cracks may render slopes more susceptible to landslides.
These areas should be avoided and appropriate warning signs should be placed, Phivolcs warned.
Batanes province has been also affected by major earthquakes in the past.
At least 18 moderate to strong earthquakes have occurred, with events up to magnitude 6.9 and maximum intensity 7 ground shaking occurred in the province from 1892 to 2016. The July 16, 2000 6.4-magnitude earthquake significantly damaged the Basco Cathedral.
Phivolcs said earthquakes in Batanes are generated by subduction activities along the Manila Trench or the East Luzon Trough. They may also be a result of movement along offshore active faults.
In addition, it said there are other nearby inland local faults, which may not be manifested on the surface, that could be potential sources of small to moderate-magnitude earthquakes.
A resident looks at damaged houses in Itbayat town, Batanes islands on Saturday, July 27, 2019. (AP Photo / Agnes Salengua Nico / MANILA BULLETIN)
According to Phivolcs science research assistant Maila Advincula, the magnitudes 5.4 and 5.9 temblors last Saturday have triggered 230 series of earthquake events, and have been slightly or strongly felt in 11 incidents.
Of the recorded series of earthquakes, 35 were plotted from their original source.
Phivolcs also pointed out that prior to the earthquakes last July 27, earthquakes with magnitudes ranging from 4.2 to 4.8 occurred from July 22 to 26. The maximum reported ground shaking intensity was 4.
It said that these earthquake events could have weakened the buildings and structures prior to the 5.9-magnitude main shock, resulting in greater damage than would have been expected.
Phivolcs reminded the public to be cautious in entering structures visibly weakened or with signs of damage by the earthquake events, as these impacts may further be aggravated by the aftershocks.
In case of houses and other buildings with visible damage, it is recommended to temporarily avoid getting into these structures, and immediately coordinate their inspection by the municipal/city engineering office.
It asked engineers from the local government, other agencies and organizations to inspect buildings and other infrastructures to determine their integrity, and recommend appropriate actions to concerned affected groups or individuals.
Likewise, slopes should be checked for tension/incipient cracks that may have resulted from the strong ground shaking. Tension cracks may render slopes more susceptible to landslides.
These areas should be avoided and appropriate warning signs should be placed, Phivolcs warned.
Batanes province has been also affected by major earthquakes in the past.
At least 18 moderate to strong earthquakes have occurred, with events up to magnitude 6.9 and maximum intensity 7 ground shaking occurred in the province from 1892 to 2016. The July 16, 2000 6.4-magnitude earthquake significantly damaged the Basco Cathedral.
Phivolcs said earthquakes in Batanes are generated by subduction activities along the Manila Trench or the East Luzon Trough. They may also be a result of movement along offshore active faults.
In addition, it said there are other nearby inland local faults, which may not be manifested on the surface, that could be potential sources of small to moderate-magnitude earthquakes.