16 active faults in Thailand pose future earthquake risks

The earthquake on March 28, 2025, caused massive destruction and underscored the dangers of natural disasters. Although the epicenter was outside Thailand, tremors felt in multiple areas highlighted the interconnected risks posed by "active faults" hidden beneath Thai soil.

Thailand is situated in a geologically complex region, with numerous faults spread across the country. Among them, several have been identified as active faults—faults with a history of past earthquakes or evidence of ongoing movement. These faults serve as potential sources of future earthquakes, posing risks to lives and property.

According to 2020 data from the Department of Mineral Resources, Thailand has 16 active faults, as follows:

1. Uttaradit Fault Group

The Uttaradit Fault Group trends in a northeast-southwest direction, tilting toward the northwest, with a length of approximately 130 kilometres. It is clearly visible from Fak Tha District, extending through Nam Pat, Thong Saen Khan, and Phichai Districts in Uttaradit Province. 

Paleoseismic studies indicate that this fault previously generated earthquakes in Ban Toita, Song Khon Subdistrict, Fak Tha District, about 3,000 years ago with a magnitude of 6.3, and in Ban Nong Thaew, Ban Fai Subdistrict, Nam Pat District, approximately 4,000 years ago with a magnitude of 7.1. More recently, on June 25, 1998, a 3.2-magnitude earthquake with an epicentre in Tha Pla District, Uttaradit, was recorded, with tremors felt in multiple districts, including the city of Uttaradit.

2. Si Sawat Fault Group

The Si Sawat Fault Group runs in a northwest-southeast direction, beginning in Myanmar and extending into Thailand through Umphang District in Tak Province, Thong Pha Phum District in Kanchanaburi Province, and Huai Kha Khaeng National Park in Ban Rai District, Uthai Thani Province. It continues through Si Sawat, Nong Prue, and Bo Phloi Districts in Kanchanaburi Province before reaching Dan Chang District in Suphan Buri Province, spanning approximately 220 kilometres in total length.

Historical seismic studies of the Si Sawat Fault reveal that an earthquake with a magnitude of 6.8 occurred about 5,000 years ago in Ban Pong Ri, Nong Ri Subdistrict, Bo Phloi District, Kanchanaburi Province.

Additionally, a significant earthquake struck the Si Sawat Fault area on April 22, 1983, with a magnitude of 5.9. The epicentre was near the Srinagarind Dam reservoir, and tremors were felt as far as Bangkok.

3. Wiang Haeng Fault Group

The Wiang Haeng Fault Group runs in a north-south direction, extending from Wiang Haeng District to Samoeng District in Chiang Mai Province, with a total length of approximately 100 kilometres. It is classified as a normal fault. 

Seismic geological data from trench investigations in Piang Luang and Mueang Haeng Subdistricts, Wiang Haeng District, Chiang Mai Province, reveal evidence of an ancient earthquake with a magnitude of 6.8. This earthquake, caused by the movement of the Wiang Haeng Fault, occurred approximately 2,000 years ago. The fault has a slip rate of 0.01–0.11 millimetres per year.

4. Ranong Fault Group

The Ranong Fault Group runs in a northeast-southwest direction, beginning in the Andaman Sea and passing through Takua Pa and Kuraburi Districts in Phang Nga Province. It continues through Suk Samran, Kapoe, Mueang Ranong, La-un, and Kra Buri Districts in Ranong Province. The fault extends further into Pathio, Sawi, Mueang Chumphon, and Tha Sae Districts in Chumphon Province.

It also runs through Bang Saphan Noi, Bang Saphan, Thap Sakae, Mueang Prachuap Khiri Khan, and Kui Buri Districts in Prachuap Khiri Khan Province, before extending into the Gulf of Thailand, east of Sam Roi Yot District in Prachuap Khiri Khan. The onshore segment of the fault is approximately 300 kilometres long.

According to the United States Geological Survey (USGS), seismic activity associated with this fault group was recorded on September 27–28, 2006, with six earthquakes ranging from 4.1 to 4.7 in magnitude. Additionally, on October 8, 2006, a 5.0 magnitude earthquake occurred. Both events had epicenters in the Gulf of Thailand, east of Sam Roi Yot District. Tremors were felt in several areas, including Hua Hin, Sam Roi Yot, Kui Buri, Pran Buri, Bang Saphan, Thap Sakae (Prachuap Khiri Khan Province), as well as Cha-am and Tha Yang (Phetchaburi Province).

5. Mae Hong Son Fault Group

The Mae Hong Son Fault Group runs in a north-south direction, beginning in Mueang Mae Hong Son District and passing through Khun Yuam, Mae La Noi, and Mae Sariang Districts in Mae Hong Son Province. It extends further south to the northern part of Tha Song Yang District in Tak Province, with a total length of approximately 200 kilometres.

Studies indicate that the Mae Hong Son Fault exhibits normal faulting with vertical displacement.

Seismic activity in this fault zone includes frequent small to moderate earthquakes. A notable event occurred on April 10, 2013, when a 5.1 magnitude earthquake struck the northern segment of the fault in Myanmar. The tremors were felt across multiple provinces in northern Thailand.

6. Mae Ing Fault Group

The Mae Ing Fault Group runs in a northeast-southwest direction, starting from Thoeng, Khun Tan, Chiang Khong, and Wiang Kaen Districts in Chiang Rai Province, extending into the Lao People's Democratic Republic (Laos). The fault has a total length of approximately 70 kilometres.

Seismic records indicate that this fault has previously experienced an earthquake in the area of Ban Pang Kha, Tub Tao Subdistrict, Thoeng District, Chiang Rai Province, around 2,000 years ago, with a magnitude of 6.7. Since 1987, five earthquakes ranging from magnitude 3.0 to 4.1 have been recorded in this fault zone. A notable event occurred on March 25, 2011, when a 4.1 magnitude earthquake took place, with tremors felt in multiple districts.

7. Mae Lao Fault Group

The Mae Lao Fault Group is oriented northeast-southwest, crossing through Mae Suai, Mae Lao, and Mueang Chiang Rai Districts in Chiang Rai Province. The fault has a length of about 80 kilometres.

The most significant seismic event in Thailand in over 150 years occurred due to movement along the Mae Lao Fault. On May 5, 2014, a 6.3 magnitude earthquake struck, with the epicenter located in Dong Mada Subdistrict, Mae Lao District, Chiang Rai Province. This earthquake caused extensive damage to homes, properties, schools, temples, and hospitals in Mae Lao, Mae Suai, and Phan Districts. Tremors were felt even in high-rise buildings in Bangkok, and more than 1,000 aftershocks were recorded.

8. Mae Tha Fault

This fault runs in a curved pattern, following the Mae Wong and Mae Tha rivers in Chiang Mai and Lamphun provinces, stretching for a total length of approximately 55 kilometres.

A study by the Electricity Generating Authority of Thailand (EGAT) in 1980 revealed that during 6 months in 1978, numerous shallow, small earthquakes occurred in the area along this fault line.

9. Mae Chan Fault Group

The Mae Chan Fault Group runs in a west-east direction, with a northern tilt and spans about 150 kilometres within Thailand. It passes through several districts in Chiang Mai Province (Fang and Mae Ai districts) and Chiang Rai Province (Mae Chan, Chiang Saen, Doi Luang, and Chiang Khong districts) and extends into the Lao PDR.

Based on geological data, the Mae Chan Fault caused a 6.9 magnitude earthquake about 1,500 years ago in the area of Nopphong Pa Kham, Pa Tung Subdistrict, Mae Chan District, Chiang Rai Province.

A significant earthquake event occurred on May 16, 2007, with a magnitude of 6.3 originating from the part of the fault in the Lao PDR. This earthquake caused damage to several buildings in Chiang Rai, such as the columns of the classrooms at Mengrai Maharat School in Mueang Chiang Rai District. The tremors were also felt in high-rise buildings in Bangkok.

10. Moei Fault Group

The Moei Fault Group runs in a northwest-southeast direction. The fault begins in Myanmar and extends into Thailand along the Moei River near Ban Tha Song Yang, Tha Song Yang District, Tak Province. It continues through Mae Ramad, Mae Sot, Phob Phra, Mueang Tak, Wang Chao districts in Tak Province, and Koh Samphian and Khlong Lan districts in Kamphaeng Phet Province, with a total length of approximately 260 kilometres.

The movement of the Moei Fault triggered a significant earthquake in Thailand on February 17, 1975, with a magnitude of 5.6. The epicenter was located at Ban Tha Song Yang, Tha Song Yang District. The tremors were felt across several northern provinces, including Bangkok.

11. Phetchabun Fault Group

The Phetchabun Fault Group runs in a north-south direction, flanking both sides of the Phetchabun Basin. The fault has a dip towards the center of the basin on both sides. Satellite images and aerial photos show that the fault line on the eastern side of the Phetchabun Basin is clearer and more continuous than the one on the western side. The fault exhibits normal fault movement and passes through Lom Kao, Lom Sak, and Mueang Phetchabun districts in Phetchabun Province, with a length of approximately 150 kilometres.

Records of earthquakes in the area show that on October 12, 1990, an earthquake with a magnitude of 4.0 occurred, and its tremors were felt in Lom Sak and Lom Kao districts of Phetchabun Province.

12. Phayao Fault Group

The Phayao Fault Group runs nearly in a north-south direction, slightly inclined to the northwest. It passes through the western part of Phan District in Chiang Rai Province, Mueang District in Phayao Province, and Wang Nuea District in Lampang Province. The fault is approximately 120 kilometres long.

The Phayao Fault caused an earthquake of magnitude 4.9 on February 20, 2019, with the tremors causing damage to houses in Wang Nuea District of Lampang Province.

13. Phu Fa Fault Group

The Phu Fa Fault Group runs in a north-south direction, dipping towards the west, and is classified as a normal fault. This fault predominantly forms a long line around the eastern side of the Phu Fa Basin. It starts at the Thailand-Laos border and extends through Thung Chang, Chiang Klang, Phu, and continues to Santisuk districts in Nan Province, with a total length of approximately 110 kilometres.

Historical earthquake data indicate that on May 13, 1935, a 6.5 magnitude earthquake occurred near the border between Thailand and Laos, which is believed to have been influenced by the movement of the Phu Fa Fault.

14. Theun Fault Group

The Theun Fault Group runs in an northeast-southwest direction, passing through Mueang Phrae, Sung Men, Long, and Wang Chin districts in Phrae Province. It continues southward through Mae Tha, Sob Prab, and Thein districts in Lampang Province, with a total length of approximately 180 kilometres.

Survey data shows that an earthquake occurred around 2000 years ago in Ban Pang Ngam, Mae Suoi Subdistrict, Wang Chin District, Phrae Province, with a magnitude of 6.6. There have been 20 reported earthquakes with magnitudes between 3.0 and 5.0 in the Theun Fault area.

15. Three Pagodas Fault Group

The Three Pagodas Fault Group is located to the west of Thailand and is particularly significant for residents in Bangkok. The fault begins in Myanmar, crossing the Thailand-Myanmar border near the Three Pagodas Pass in Sangkhla Buri District, and continues through Thong Pha Phum, Si Sawat, and Mueang Kanchanaburi districts, eventually ending in Dan Makham Tia District, Kanchanaburi Province, covering a total length of about 200 kilometres.

Historical fault movement data from the Tipuye area, Chalae Subdistrict, Thong Pha Phum District, indicate that an earthquake of 6.4 magnitude occurred approximately 2,000 years ago. The most recent historical earthquake from this fault happened about 1,000 years ago with a 6.4 magnitude near Kaeng Kaep in Si Sawat District, Kanchanaburi Province.

16. Khlong Marui Fault Group

The Khlong Marui Fault Group is a strike-slip fault that runs parallel to the Ranong Fault Group, with left-lateral displacement, and vertical movement typical of a reverse fault. The fault begins in the Andaman Sea, off the eastern coast of Phuket Island and Yao Island, in Phang Nga Bay.

It extends onto land, passing through Khlong Marui, Tab Pud, Takuatung, and Tai Muang Districts in Phang Nga Province. The fault continues into Phanom, Kiri Rat Nikhom, Ban Tak Khun, Wiphawadi, Tha Chang, and Chaiya districts in Surat Thani Province, with the length on land approximately 140 kilometers.

Seismic Activity in the Area:

September 4, 2008: Magnitude 3.1, epicentre in Phanom District, Surat Thani Province.

December 23, 2008: Magnitude 4.1, epicentre in Phra Sang District, Surat Thani Province.

April 16, 2015: Magnitude 4.3, epicentre in Srisunthorn Subdistrict, Thalang District, Phuket Province, causing minor damage to several homes. The quake was felt throughout Phuket Island.

May 7, 2018: Magnitude 4.5, epicentre in the sea near Yao Island, Koh Yao District, Phang Nga Province, felt in Phuket, Phang Nga, and Krabi provinces.