The 6.3-magnitude earthquake which struck Chiang Rai on Monday was the largest ever with its epicentre in Thailand, the Engineering Institute (EIT) said yesterday.
It was significantly more powerful than the previous record holder, a 5.9-magnitude tremor recorded on April 22, 1983 near Kanchanaburi's Srinakarind dam.
Monday's earthquake occurred in an active fault zone, and its effects were felt more heavily because the epicentre was only seven kilometres underground, the EIT said.
Most of the buildings damaged by the quake were ones which do not meet modern earthquake design standards, the institute said. Those within a 30km-radius of the epicentre suffered the most severe damage.
To prevent further damage to buildings that may be caused by aftershocks, the EIT suggested house and building owners fill cracks in concrete posts and beams with plaster.
Buildings on mountain slopes need full structural inspections to assess the damage caused by the quake, the agency added. Dams and reservoirs within 200km of the earthquake's epicentre will be examined every six hours for the next three days.
Some damage might not be visible to the human eye, and specialised equipment must be used to check for structural problems, the EIT said. Authorities were also advised to monitor possible aftershocks.