Geohazards

From Boise State - Geoscientists Without Borders

A recent workshop and report summarized the earthquake hazards for all of Southeast Asia and defined northern Thailand as a high seismic hazard zone (Peterson et al., 2007). This workshop and report concluded that the area surrounding Chiang Mai, Thailand contains many active crustal faults. The Chiang Mai basin is the largest intermontane basin in northern Thailand. Modern floodplain deposits lie upon Tertiary basin fill (e.g., Figure 1; Grissemann et al., 2004) and the basin is prone to ground shaking from earthquakes near and far (Peterson et al., 2007). Several M=5 earthquakes have originated in the basin, and a number of faults within 150 km of Chiang Mai city show evidence of Quaternary-aged activity (Kosuwan et al., 2006, Rhodes et al., 2004; Fenton et al., 2003). Detailed fault studies and shaking-hazard studies are needed to properly evaluate the earthquake hazard for this populated region: a region that is presently undergoing new construction of multi-storied buildings, transportation infrastructure, and dams. We have selected a site along the 110-km trace of the Mae Tha fault where the fault crosses Quaternary alluvium and deeper basin strata. This site, about 25 km east of Chiang Mai city, is in dry rice-field areas that are easily accessed. The Mae Tha fault is suspected to be active (Kosuwan et al., 2006) and is important to understanding neotectonics of the basin; however, little is known of its Quaternary slip history. Imaging of the faulted and associated strata will contribute to understanding the slip rate and recurrence of earthquakes on this structure. We will consult with Chiang Mai faculty and the Thai Department of Mineral Resources (Environmental Geology Division) to finalize permission to access this site. Geophysical analyses for this field site include, but are not limited to, seismic reflection, seismic refraction, GPR, gravity, magnetics, and electrical methods.

Reference Papers

• Grissemann, C., Schuck, A., Seidel, K., Lange, G., and Tantiwanit, W., 2004. Geophysical signatures of the abandoned waste disposal sites Mae Hia and Nog Harn, Chiang Mai. In: Proceedings of the International Conference on Applied Geophysics, Chiang Mai, edited by: Rieb, S., Wongpornchai, P., and Chantraprasert,S., Department of Geological Sciences, Chiang Mai University. p. 50-59.
• Kosuwan, S., Saithong, P., Lumjuan. A., 2003, Paleoearthquake on the Mae Ai Segment of the Mae Chan Fault Zone, Chiang Mai, northern Thailand: Report of Geological Survey Division, Department of Mineral Resources, 57 p. (in Thai with English abstract)
• Kosuwan, S., Takashima, I., and Charusiri, P., 2006, Active fault zones in Thailand. 6 p., available at http://www.dmr.go.th/geohazard/earthquake_n/ActiveFault_Eng.htm.
• Peterson, M., Harmsen, S., Mueller, C., Haller, K., Dewey, J., Luco, N., Crone, A., Lidke, D., and Rukstales, K., 2007, Documentation for the Southeast Asia Seismic Hazard Maps, U.S. Geological Survey Administrative Report September 30, 2007, 65p., http://apps.develebridge.net/usiotws/4/USGS_SEASIA-SeismicHazards_Sep07.pdf
• Rhodes, B.P., Conejo, R., Benchawan, T., Titus, S., and Lawson, R., 2005, Palaeocurrents and provenance of the Mae Rim Formation, Northern Thailand: implications for tectonic evolution of the Chiang Mai basin, Journal of the Geological Society, London, Vol. 162, 2005, pp. 51–63, http://geology.fullerton.edu/brhodes/rhodes%20et%20al%202005%20jgsl.pdf.
• Rhodes, B.P., Perez, R., Lamjuan, A., and Kosuwan, S., 2004, Kinematics and tectonic implications of the Mae Kuang Fault, northern Thailand. Journal of Asian Earth Sciences, 24 (1), p.79-89, http://geology.fullerton.edu/brhodes/rhodes%20et%20al%20-%202004.pdf.