Hydrogeophysics

From Boise State - Geoscientists Without Borders

A site in the developing industrial area of Saraphi and Lamphun, 10 km south of Chiang Mai city will be selected for a demonstration MASW (multi-channel surface wave analysis) method of determining Vs30, an accepted parameter for mapping potential earthquake shaking hazard in an urban basin (ICC, 2000). This site is in the central alluvial plain of the Chiang Mai basin Margane and Tatong, 1999), an area where low Vs30 (shaking amplification) is suspected in parts of the geologically-recent alluvial section.

This same area south of Chiang Mai city will also be used for 2D seismic reflection, and other methods of imaging of aquifer units, as this is the area of highest groundwater exploitation potential, and also an area highly vulnerable to groundwater pollution (Margane and Tatong, 1999). Little is known of the aquifer structure in this area, and imaging of the aquifer units will be a useful tool for groundwater management and protection in this area. The actual site will be dictated by availability of geotechnical test wells or water wells that can be used for a VSP study, and for direct shear-wave velocity measurements to verify or calibrate surface methods. The large agricultural fields of this area will be dormant during the January dry season, and should provide a good site for long profiles, and electrical and seismic arrays relatively free of cultural noise. Previous work by Klaytae and Singharajwarapan (2004), and Grissemann et al. (2004) indicate that good quality resistivity and high-resolution seismic data can be obtained in this area.