Cracks in the ground
The Kaeng Sua Ten dam straddles the Mae Yom or Sa-iab seismic fault line, which is a branch of the Phrae fault zone, although it is not clear how long it has been since the Mae Yom fault last produced an earthquake. In November 1996, the Geology Department released results of seismic studies, which revealed an active fault line 31 km from the dam site.
The Phrae fault zone, located less than 50 km from the dam site is active and has produced 20 earthquakes over the last 15 years. On 9 December 1995, an earthquake measuring 5.1 on the Richter scale rattled Phrae province, cracking buildings and toppling & pagoda.
The building of large reservoir is can cause earthquakes by putting huge amounts of pressure on underlying seismic faults, known as reservoir-induced seismicity. Research in Thailand by the Electricity Generating Authority of Thailand (EGAT) shows that the construction of the Khao Laem and Sdnakhadn dams in Kanchanaburi province led to thousands of small earthquakes, and dozens of larger ones, in the Three Pagodas Fault Zone. A 'revised' report submitted by the RID in May 1995 was again dismissed by OEPP officials as being too confusing and put together from several studies by various agencies such as ECAT and the forestry
Dr. Pdnya Nutalai, a geologist at the Asian Institute of Technology, and a member of the subcommittee studying the proposed dam, said that the inactive Mae Yom fault may be reactivated by the pressure of the large amount of water to be stored in the Kaeng Sua Ten reservoir.
An expert with the Department of Mineral Resources said a full and proper investigation of issues concerning the risks of reservoir-induced seismicity would take about a year to complete and involve foreign specialists since no Thai geologist has ever done intricate seismic study. Project proponents say that technology is available to make it safe, although incorporating the technology will increase costs by more than 30 percent.