Scientific and technical design and deployment of long-term subseafloor observatories for hydrogeologic and related experiments, IODP Expedition 301, eastern flank of Juan de Fuca Ridge

Abstract

Integrated Ocean Drilling Program (IODP) Expedition 301, on the eastern flank of the Juan de Fuca Ridge, established part of a three-dimensional network of borehole observatories (Circulation Obviation Retrofit Kits CORKs) in the oceanic crust. These observatories are to be used to conduct active, multidisciplinary experiments over timescales of minutes to years and length scales of meters to kilometers. The complete experimental program will comprise two IODP expeditions (the first having been Expedition 301, the second to be scheduled), an offset seismic experiment, and long-term monitoring and crosshole testing carried out by submersible and remotely operated vehicle. During Expedition 301, we replaced a preexisting CORK observatory in Hole 1026B and created and instrumented new Holes U1301A and U1301B, which penetrate 108 and 320 m into basement, respectively. The borehole observatories deployed during Expedition 301 share some characteristics with systems deployed during the Ocean Drilling Program but also include many improved components and novel features.