The first small network of borehole strainmeters in Taiwan was completed in February by a group from DTM that included Selwyn Sacks, Alan Linde, Nelson McWhorter, and Michael Acierno. In collaboration with Chi-Ching Liu and others from the Institute of Earth Sciences of Academia Sinica, the DTM team worked with drill operators to install a third strainmeter to complement two previously installed instruments near the Longitudinal Valley in eastern Taiwan. During a typical strainmeter installation, a small drill rig (pictured below) bores a hole to approximately 200-meter depth. Using the same rig, the instrument is then lowered into expansive grout material previously emplaced in the lower part of the hole. Once the grout cures and the strainmeter becomes cemented into position, the instrument can sense minute strain changes very accurately over time, revealing important information about the deformation of the surrounding material.

It is recognized that east-central Taiwan is deforming and building mountains extremely rapidly. This unusual behavior can be ascribed to the action of the collision of two tectonic plates near Taiwan's coast. As DTM scientist Selwyn Sacks describes it: "The Philippine plate, converging at about 7 centimeters per year, is compressing the island rather than subducting beneath it, as it does everywhere else." Using suites of instruments similar to those installed by DTM and Academia Sinica, scientists will be able to make observations about the behavior of the materials accommodating the rapid deformation. A secondary goal of the project is to test the performance of strainmeters modified for installation in the kind of sediment-rich and poorly consolidated rock environment that characterizes this and most other areas of Taiwan. Future plans for the project include expanding the first network and installing another network of instruments to the north in a different geological setting from that visited this February. (Photos by Michael Acierno & Selwyn Sacks)