Nanostrain sensitivity core hole extensometer for in situ rock parameter measurements

A mechanical strainmeter is described that will resolve nanostrain effects in host rock. It is loaded into a 26 mm diameter core hole, measuring strains deep in that hole over an interval of 1 m. Typical stability, once settled, is 5 parts in 1010 per hour drift. The resolution of the electrical output signal is at least 1 nm with frequency response set for DC to 1 Hz.