This research is under the umbrella of Taiwan Chelungpu-fault Drilling Project (TCDP) and seeks to provide stratigraphic data of the boreholes in facilitating the interpretation of structural fabrics seen in the drill bores. The major scientific objective of TCDP is to understand the reason why abnormally large fault-slip occurred during the 1999 Chi-Chi earthquake. Two boreholes, TCDP-A and B of 40 meters apart, were drilled and the deepest hole, TCDP-A, reaches a drill depth of 2003 meters and continuous cores of 1571 meters in the range of 432 to 2003 meters, were recovered. The TCDP-B borehole reaches a total depth of 1350 meters while full cores in the range from 950~1350 meters were retrieved. A sidetrack of 1300 meters in drill depth was drilled at Hole B with the kickoff point at 950 meter. Full cores from 1100~1300 meters from this sidetrack were recovered. In addition to the recovered cores or ditch cuttings, a suite of well logs of oil-industry standards was collected at each of the well bore.
We established a lithostratigraphic column for the TCDP-A well and successfully correlated the well-bore rock succession to its surface equivalent. Our results find that the most likely Chi-Chi rupture encountered at 1111 meter at TCDP-A occurs in the Chinshui Shale while its surface equivalent occurs near the base of the Cholan Formation, indicating that the Chi-Chi rupture cuts upsection in the direction of faulting transport.
The TCDP drilling recovered up to 2170-meters cores of shallow marine siliciclastics accumulated in the latest Miocene to Pleistocene foreland basin. The exceptionally continuous cores provide us a rare opportunity in deciphering the interplay between the tectonic and sedimentary factors that govern the foreland sedimentary architecture.
The relevant publication for this project is:
Cheng, P.-H., Lin, A.T. , Ger, Y.-I., Chen, K.-H. 2006. Resistivity structures of the Chelungpu Fault in the Taichung area, Taiwan . Terrestrial, Atmospheric and Oceanic Sciences, 17(3), 547-561.
Lin, A.T., Wang, S.-M., Hung, J.-H., Wu, M.-S., Liu, C.-S. 2007. Lithostratigraphy of the Taiwan Chelungpu-fault Drilling Project-A borehole and its neighboring region, central Taiwan . Terrestrial, Atmospheric and Oceanic Sciences , 18(2), 223-241.
Chiang, C.-W., Unsworth, M., Chen, C.-S., Chen, C.-C., Lin, A.T. , Hsu, H.-L. 2008. Fault zone resistivity structure and monitoring at the Taiwan Chelungpu Drilling Project (TCDP) . Terrestrial, Atmospheric and Oceanic Sciences 19(5), 473-479, doi:10.3319/TAO.2008.19.5.473(T).