Summary

Analysis of current stress distribution and slip tendency of existing faults impacted by fluid injection related to oil exploitation in the coastal area from Tuy Hòa to Vũng Tàu

Đỗ Văn Lĩnh, Nguyễn Lợi Lộc, Đinh Quốc Văn, Vũ Trọng Tấn, Nguyễn Xuân Huy,
Đinh Quang Sang, Nguyễn Thị Thu Thủy, Nguyễn Thanh Sang, Vũ Thị Ngân Thảo

Slip tendency analysis provides a means to that assess the relative risk of earthquakes, the active ability of faults, and check compatibility geological structures in a stress field. It’s an approach to explore new high-risk and earthquake-prone faults, and an alternative oriented solution to stress vector - that interpret true fault surfaces from earthquake focal mechanisms as well as orientation for prospecting and exploiting petroleum minerals and water. Through the normalization of friction coefficient 0.55 (angle about 28.56⁰) by the conjugate angles method and the modeling system with specialized softwares, the faults of the NNE- SSW (strike of 10 - 30⁰) in the coastal area from Tuy Hoa to Vung Tau are considered to have a high slip tendency (Ts is ranged 0.7-1.0) for present tectonic stress fields. When the injection pressure exceeding the critical threshold of the injection gradient from 0.001 to 1.3 bar/10m (exceeding the threshold of hydrostatic pressure at considering depth), it can cause slip faults and triggered earthquakes with a maximum magnitude of 4.2 Richter. Research results are consistent with earthquake observations from 2002 to 5/2020 (315 recorded events) with the magnitude from 1.5 to 4.2 Richter.

Keywords: fault, slip tendency; stress tensor, coefficent of friction, angel of friction, earthquake focal mechnism, activities of human