oa Electric Modelling and Imaging of Sinkholes Developed after the 26 December 2004 Tsunami in the Karstic Limestone in Southern Thailand

Southern Thailand has a distinguishing karst topography, which is underlain by soluble carbonate rocks with various systems of karsts. Sinkholes represent a common geohazard associated with karst terrain, and in reality they are found in many areas in Southern Thailand such as Krabi, Chumphon, Narathiwat, Phangnga, Yala, Ranong, Songkhla, Satun and Trang. The catastrophic 26th December 2004 tsunami and earthquake of 9.3 Richter have shaken many South and Southeast Asian countries, including Southern Thailand. This paper presents the results of an investigation, jointly conducted by the Asian Institute of Technology and Department of Mineral Resources of Thailand, aimed at detection of the sinkholes in carbonate rocks in the Southern Thailand, which were triggered by the 26 December 2004 tsunami. As reported, the largest of the eighteen sinkholes found in early January 2005 by the Department of Mineral Resources, Thailand (DMR) is in Nakhon Si Thammarat province, measuring 20 meters in diameter and 10 meters deep. In this paper, a brief review on sinkhole formation and data related to karst topography as well as main mechanism of sinkhole collapses in Trang and Satun provinces are presented. Electric modeling was done to study on the effectiveness of the electric imaging technique. Results of some field surveys are analyzed and shown.