Subsurface temperature measurements for detecting tectonic dislocations

An example of characterization of a tectonic zone by using underground temperature measurements is presented. A tectonic discontinuity, located in NW Italy, was investigated by precision temperature measurements by means of the analysis of thermal data recorded in a monitoring well along the northern part of Torrente Traversola Deformation Zone. Moreover, we investigated the lateral extension of the deformed zone by means of the analysis of thermal logs recorded in three control wells located at some distance from the tectonic structure. The monitoring well and the three control wells show completely different thermal pattern. The former exhibits advection and a thermal profile that can be well matched with a model of fluid flow within a sub-vertical fracture. The control wells instead reveal prevailing conductive thermal regime. This might be evidence that the deformation zone has little lateral extension. Our study showed that high-precision temperature logs can be a valuable tool for detecting fractured zones and delimit their lateral extent.