Seismic refraction tomography of Mae-Hia landfill sites, Mueang District, Chiang Mai

Abstract

The groundwater contamination from the unmanaged abandoned landfill site creates many problems to the community surrounding the landfill site. An abandoned landfill site in Mae-Hia Sub-district, Mueang District, Chiang Mai Province is an example of the unmanaged landfill site. Remedial work of groundwater quality needs to understand the geologic conditions. The seismic refraction survey and tomography provide the solution to delineate the geologic conditions. Seven lines of seismic refraction survey were performed using broadside configuration over an area of approximately 0.12 square kilometer. The refraction data was process as travel-time curves to display the two-dimensional velocity model. The refraction tomography shows both two-dimensional velocity model at a particular depth and three-dimensional velocity model of the shallow subsurface structure. The result demonstrates that the Mae-Hia landfill site has three layers. The upper layer was interpreted as topsoil having a wave velocity range from 124 to 849 meters per second and a thickness of 1.2 to 9 meters. The middle layer was interpreted as waste material and clayey sand having a wave velocity range from 600 to 1,719 meters per second and a thickness 2 to 13.9 meters. The lower layer was interpreted as saturated sand and saturated sand and gravel at the base of the landfill site. It has a wave velocity range from 1,351 to 2,000 meters per second and a thickness of 1.5 to more than 6.5 meters.