Site: JT-1C

To 186 Site JT-1C Track Line

To 186 KH96-3 Line 1

To 186 KH96-3 Line 4

Priority: 1
Position: 39°10.911ŽN, 143°19.927ŽE
Water Depth: 2605 m
Sediment Thickness: ~1300 m
Target Drilling Depth: 1000-1400 mbsf
Approved Maximum Penetration: 1400 mbsf
Seismic Coverage: Intersection of KH96-3 Lines 1 and 4 at CDP 2337 on Line 1

Objectives: The objectives of Site JT-1C are:

  1. Install long-term geophysical borehole observatory to monitor strain, seismicity, tilt, pressure, and temperature. Quantify episodic plate motions within seismically active part of the interplate seismogenic zone.
  2. Recover past 3-m.y. volcanic-ash stratigraphy for comparison with other western Pacific ash deposits in relation to eruptive processes and transport mechanisms.
  3. Constrain subsidence history of the Japan Trench forearc.
  4. Determine nature of Cretaceous basement.

Drilling Program: Double APC to 250 mbsf, XCB to 450 mbsf, RCB to 1000 mbsf and deeper, if time permits. Drill 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); turbidite sand 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).

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