Installation of the first Strainmeter Instrument

Overview

March 15, 2005

After many months of planning and preparing, today marks the beginning of a new stage in the Plate Boundary Observatory project: installation of the first PBO strainmeter instrument.

The strainmeter arrived in the United States on March 8, 2005, after surviving a plane trip from Brisbane, Australia via Korea, where it sat for several days after being bumped by shipments of fresh fruit. In the days following the arrival of the instrument, Mick Gladwin of GTSM Technologies, PBO’s borehole strainmeter vendor, performed a series of careful tests to ensure the strainmeter had not been harmed during transport. PBO crews are now ready to install this first strainmeter into one of the eight boreholes recently drilled in the Pacific Northwest.

Today crews arrived at the borehole site located at a Hoko Falls Fish Hatchery in Sekiu, Washington, chosen because of its solid bedrock, easy access to power, and its location on the highest areal strain field (based on the models). After crews laid down large polyethylene rubber mats on the soft ground surrounding the borehole to keep the heavy truck wheels from sinking into the mud, the engineers unloaded and unpacked from the trucks all the installation equipment.

The first step was to measure the exact depth of the borehole and ensure the 500+ feet was clear of any debris. To do this, crews set up a hoist truck over the hole and a lowered into the hole a 35-lb weight attached to a cable. Via careful careful measurement, the total depth of the hole was confirmed to be at 546’ 8.5”.

Next, the engineers assembled a 30-foot dump bailer and tested its functionality with a test run down the hole. The last step of the day was to determine the set up of the hydraulic capstan and shive, which will be used to carefully lower the instrument into the hole for placement. Although there are many obstacles to overcome when lowering such an important instrument almost 550 feet into the ground, crews were able to find just the right positioning for all pieces of equipment. If all continues to run smoothly, crews plan on installing the strainmeter instrument tomorrow.