a vertical hydraulic fracture was initiated in a borehole at a depth of 3000 ft. assume the ground is saturated continuously from the surface and that the pressure in the ground water is hydrostatic. the water pressure was first raised to 710 psi above the original ground water pressure (1300 psi) and then it was not possible to raise it further. when pumping stopped, the water pressure fell to a value 110 psi above the original ground water pressure. after a day, the pressure was raised again, but it could not be pumped to a value higher than 100 psi above the previous pressure. estimate: 1. vertical pressure at the test site 2. tensile strength of the rock 3. horizontal stresses (with and without pore pressure) at the test site