九二一地震引發車籠埔斷層錯動破裂，造成嚴重災情，引起國際科學界極大的重視。在台中大坑地區將進行2公里車籠埔斷層深井鑽探計畫，探討車籠埔斷層巨量錯動之原因。本研究使用直流電阻法及大地電磁法在井址位置及其周圍附近研究地表下的電性構造，共完成8條電阻率影像探測剖面與25個大地電磁探測測點。 RIP施測結果指出，測區內紅土台地的厚度分佈，西側較東側薄。車籠埔古斷層向東傾斜40?~45?。下盤是更新世頭嵙山層與洪積層及全新世的堆積層。上盤是上新世岩層，上覆紅土化階地堆積層。在九二一地震地表破裂處之下的破裂帶呈向東傾斜40?~45?。上盤與下盤都屬於上新世地層。在車籠埔深鑽井址上所做MT施測結果指出，井址下有兩處電阻率較低的電性層，在深度470~520公尺處的低電阻層可能是卓蘭層中的細砂或頁岩層，在深度650~1250公尺處的低電阻層可能是錦水頁岩層，研判錦水頁岩底面可能在1100~1250公尺間，鑽探結果可能會在此處發現車籠埔斷層。對全區的MT施測結果可以描繪出全區地下電性地層的分佈情形並研判出921地震斷層面位置。921地震斷層面向東南方傾斜，南面較北面來的深。 The electric resistivity method and the magnetotelluric method are used. Total of 25 MT measurements and 8 RIP profilings were carry out in the study area. By RIP surveying, we get the distribution of the thickness of the Lateritic Deposit which is about 60 m thick in the east and thicker than the west. The RIP prospecting results show that the old Chelungpu fault has a dipping angle of 40?~45? to the east. The strata on the footwall are Pleistocene and the strata on the hanging wall are Pliocene. The 921 earthquake fault has a dipping angle of 40?~45? to the east. The strata on hanging wall and the footwall of the fault plane are all the Pliocene. The MT prospecting results at the TCDP size show that there are two low resistivity layers. One is at the depth of 470~520 meters and the other is at the depth of 650~1250 meters. The low resistivity layer at the depth of 470~520 meters may be a fine sand or shale formation of the Cholan Formation and the low resistivity layer at the depth of 650~1250 meters may be the Chinshui Shale. The bottom of the Chinshui Shale may be at the depth of 1100~1250 meters and where may be the the fault plane of the 921 earthquake.By surveying in the whole study area, we can delineat the electrostraigraphic features and recognize the geometry type of the 921 earthquake fault surface. It shows that the fault plane dips to the southeast and the depth in the south is depther than in the north.
