Site: JT-2G

To 186 Site JT-2G Track Line

To 186 KH96-3 Line 2

Priority: 1
Position: 38°47.75ŽN, 143°21.9ŽE
Water Depth: 2245 m
Sediment Thickness: ~1300 m
Target Drilling Depth: 1000-1600 mbsf
Approved Maximum Penetration: 1600 mbsf
Seismic Coverage: North of intersection of KH96-3 Line 2 and KH90-1 Line JT90; at CDP 1430 on Line 2

Objectives: The objectives of Site JT-2G are:

  1. Install long-term geophysical borehole observatory to monitor strain, seismicity, tilt, pressure, and temperature. Quantify episodic plate motions within seismically inactive part of the interplate seismogenic zone.
  2. Constrain subsidence history of the Japan Trench forearc.
  3. Determine nature of Cretaceous basement.

Drilling Program: APC to 250 mbsf, XCB to 450 mbsf, and RCB to 1000 mbsf and up to 600 m deeper, if time permits. Drill the instrumented borehole to ~1000 mbsf, install reentry cone, and case through unstable section.

Logging and Downhole Operations: Triple combo, FMS/sonic/temperature, BHTV; install long-term sensor package and cement at the bottom.

Nature of Rock Anticipated: Sandy, silty, pebbly clay with ash layers (50 m); clayey diatom ooze, diatomaceous clay, ash layers (~350 m); diatomaceous claystone, clayey diatomite (~250 m); claystone, diatomaceous claystone, calcareous claystone (~200 m); sandy claystone, diatomaceous claystone (~200 m); turbidites and silty claystone (~100 m), sandstone and siltstone (~100 m), boulder to pebble conglomerate and breccia, dacite and mudstone clasts (~50 m); and silicified claystone (~100 m).

To 186 Site JT-3

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