Stress orientation and tectonic regime in the northwestern Valencia Troughfrom borehole data

The orientation of the maximum horizontal stress SH is Obtained from the an alysis of borehole breakouts, covering a depth range from 300 to 3415 m (be low sea level) in twelve offshore exploration wells in the northwestern Val encia Trough. The orientation of SH is roughly coincident with the strike o f major extensional structures. From N to S it changes counterclockwise fro m a NE-SW orientation to a N-S orientation. Estimates of the tectonic regim es indicate that the area is characterised predominantly by normal-faulting with a strike-slip component. Both the stress orientations and the tectoni c regimes are consistent with neotectonic studies in the nearby Catalan Coa stal Ranges. An established method of estimating the tectonic regime by Moo s and Zoback (1990) was modified by the inclusion of a nontrivial cohesion, but this changes the results insignificantly. (C) 1998 Elsevier Science B. V. All rights reserved.