Resistivity structures of the Chelungpu fault in the Taichung area, Taiwan

Ping Hu Cheng, Andrew Tien Shun Lin, Yueh Iuan Ger, Kuan Hung Chen

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3 Scopus citations


We conducted magnetotelluric prospecting in the Taichung area to investigate subsurface resistivity structures of the Chelungpu fault and the resistivity of rock formations. The results indicate that the Chelungpu fault is a complex fault system consisting of two major fault zones, several fracture zones, and back thrust. The two major fault zones, the basal and the Chi-Chi fault zone are about 800 m apart on the ground and converge to a narrow band at a dep1h of 3000 m. The fault zones are not smooth, composed of ramps and platforms with an average eastward dipping angle of 35° - 37° within the depth of 3000 m. In the shallower region, the basal fault zone has developed along the boundary of the Toukoshan Formation (resistivity: 200 - 400 Ω - m) at the footwall and the Neogene formations on the hanging wall, wheire the Cholan Formation, the Chinshiu Shale, and the Kueichulai Formation have respective resistivity mainly in the ranges: 40 - 100, 8 - 60, and 50 - 150 Ω - m. While the Chi-Chi fault zone has developed along the weak layers of the Cholan Formation where resistivity is lower than the unsheared block. At the TCDP site, the use of MT soundings, prior to TC DP drilling, predicted the position of the Chi-Chi fault zone to be at a depth between 1100 m and 1250 m. Drilling subsequently confirmed this result, indicating MT sounding to be a reliable approach in revealing subsurface structures.

Original languageEnglish
Pages (from-to)547-561
Number of pages15
JournalTerrestrial, Atmospheric and Oceanic Sciences
Issue number3
StatePublished - Sep 2006


  • Chelungpu fault
  • Magnetotellurics
  • Resistivity structures


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