AFTER a 4.5 magnitude earthquake rocked Phisanulok and was felt in Phichit and Kamphaeng Phet provinces at 12.17 a.m. today (June 29) an academic pointed out that buildings in this zone should be strengthened as a ministerial regulation governing seismic resistance of structures was only enforces in 2021, Naewna newspaper said.
Amorn Pimanmat of Kasetsart University’s engineering faculty said this was a medium magnitude earthquake but because it was shallow, being 5 kilometres deep at its epicentre in Phitsanulok’s Phai Lom subdistrict, Bang Krathum district, vibrations were felt across this province as well as nearby Phichit and Kamphaeng Phet provinces.
Earthquakes occur infrequently in this area with two having struck over the past 30 years including last night’s tremor with there being two known fault lines – Uttaradit and Phetchabun – in this zone.
“However preliminary data shows that this quake’s epicentre is far from the two fault lines and could have been caused by a different as yet undetected fault line – also known as Blind Fault. However we have to wait for detailed geological data first,” he said.
A 4.5 magnitude quake at a shallow depth of not more than 5 km will lead to vibrations shaking buildings and other structures with cracks developing in those not up to standard.
At risk are ancient buildings such as temples built with bricks and those with shallow piling.
However buildings built according to engineering principles with steel reinforcement used and pillars and beams being as calculated by engineers are unlikely to be affected but the owners should inspect them as a precautionary measure.
Amorn pointed out that prior to 2021 the lower northern region was not classified as an earthquake prone zone with past statistics showing only a few tremors had occurred.
However further study led to the Public Works and Town & Country Planning Department issuing an ministerial regulation that buildings in this zone should have seismic resistance with Phichit being at first level and Kamphaeng Phet the second level. Thenceforth buildings, especially those taller than 15 metres, are required to be built to withstand quakes.
However the point is that this ministerial regulation has only been enforced for two years with there being lots of buildings built before then not designed to withstand quakes.
Top: A graphic image showing cracks caused by an earthquake by by Htc Erl from Pixabay
Front Page: A seismograph machine needle drawing a line depicting seismic and earthquake activity. File photo: Getty Images and published by NBC Bay Area