The Mineral Resources Department is analysing the Nakhon Nayok Fault to determine if it is active and the result will be announced next year, Lertsin Raksasakulwong, director of the Environmental Geology Division, said yesterday.
The Mae Ing and Phetchabun faults will be put on the department's list this year, he said.
The Mae Ing Fault has experienced a tremor stronger than 4.0 magnitude, while the Phetchabun Fault has spawned a quake greater than 5.0.
The Tha Khaeg Fault, which runs mainly in Laos and was last active more than 30 years ago, has been taken off the department's hot list.
There remain 13 faultlines in 22 provinces, including Mae Chan in Chiang Rai and Chiang Mai; Mae Hong Son; Meoi in Tak and Kamphaeng Phet; Mae Tha in Chiang Mai, Lamphun and Chiang Rai; Thoen in Lampang and Phrae; Phayao in Phayao, Chiang Rai and Lampang; Pua in Nan; Uttaradit; and Three Pagodas in Kanchanaburi.
The other is Si Sa Wat in Kanchanaburi, Suphan Buri and Uthai Thani. The Tha Khaeg Fault will soon be officially deleted from the 13-fault list. The inclusion of Mae Ing and Phetchabun will make a total of 14.
The twin quakes felt in Phuket on Monday resulted from two quakes on April 11 near Aceh off Sumatra at 8.9 and 8.2 magnitude, which were followed by more than 40 aftershocks.
The Phuket quakes travelled through two faultlines - Ranong and Khlong Marui, which are on the hot list of 14 faultlines.
There were nine mild aftershocks yesterday following the quakes in Phuket on Monday, which damaged 35 homes on the island, said Nithas Phoowatthanakul, director-general of the Mineral Resources Depart-ment.
The aftershocks, measuring 2.1-2.7 on the Richter scale, were felt throughout the province although the twin quakes on Monday were strongest at Tambon Si Sunthorn in Thalang district. The final shock came at 12.18pm and was measured at 3.1, he said.
The first 4.3 quake struck Phuket at 4.44pm on Monday, followed two minutes later by the 5.7 quake.
"Both quakes were separate |phenomena, not that the second |was subsequent to the first," he added.
A strong quake in the South connecting the Ranong and Khlong Marui faultlines could cause collapse of land in provinces where the topology consists mostly of limestone - Krabi, Trang and Satun in the South and Kanchanaburi in the West, said Thinnnakorn Thathong, another senior department official.
"A quake of 3 to 5 magnitude may shake or crack homes with weaker structures, but buildings with greater strength or those with anti-quake measures should not be affected," he added.
After the 9.1 quake in 2004, with its epicentre in Aceh, spawned a tsunami that caused continent-wide damage and killed hundreds of thousands of people, some quakes associated with the Ranong and Khlong Marui faults have been recorded.
Three larger ones were a 5.0 quake east of Prachuap Khiri Khan's Sam Roi Yot district in 2006, a 3.2 quake in Surat Thani's Muang district in 2008 and a 2.7 tremor in Phang Nga's Takua Pa district in February of this year.