Method and apparatus for monitoring growth of fracture during hydraulic fracturing treatment of a ground formation. A series of tiltmeters are positioned at spaced apart tiltmeter stations at which tilt changes due to hydraulic fracturing treatment are measurable by those tiltmeters. Tilt measurements obtained from the tiltmeters at progressive times during the fracture treatment are compared with estimated tilt changes estimated from an assumed hydraulic fracturing propagation. Useful values for initially undetermined values of parameters of the model are derived using an inverse procedure. The data analysis may be performed in real time as the hydraulic treatment progresses using differing propagation models to determine a most probable model.