Study on in-situ stress measurement around coastal marginal land in Fujian

Abstract

The in-situ hydraulic fracturing stress measurements have been carried out around the coastal marginal land in Fujian Province. And the characteristics of magnitude, direction and distribution of tectonic stress have been obtained. Based on the observed stress data, the characteristics and activities of fault zones are analyzed and studied in the paper according to the Coulomb friction criteria. (1) The maximum horizontal principal compressive stress is in the NW-WNW direction from the north to the south along the coastline verge, which is parallel to the strike of the NW-trending fault zone, consistent with the direction of principal compressive stress obtained from geological structure and across-fault deformation data, and different from that reflected by focal mechanism solution by about 20°. (2) The horizontal principal stress increases with depth, the relation among three stresses is S H>S v>S h or S H≈S v>S h, and the stress state is liable to normal fault and strike-slip fault activities. (3) According to Coulomb friction criteria and taking the friction strength μ as 0.6–1.0 for analysis, the stress state reaching or exceeding the threshold for normal-fault frictional sliding near the fault implies that the current tectonic activity in the measuring area is mainly normal faulting. (4) The force source of current tectonic stress field comes mainly from the westward and northwestward horizontal extrusions from the Pacific and Philippine Plates respectively to the Eurasian Plate.