A series of hydraulic-fracture experiments using a downhole tiltmeter array, called an inclinometer array, was conducted at the Department of Energy (DOE)/Gas Research Institute (GR!) Multi-Site facility in Colorado. The inclinometer array was used to measure the deformation of the reservoir rock in response to hydraulic fracture opening and confirm microseismically measured results. In addition, the inclinometer array was found to be a useful tool for accurately measuring closure stress, measuring residual widths of both propped and unpropped fractures, estimating proppant distribution, and evaluating values of in situ moduli.