Contemporary crustal stress in the Guangdong-Hong Kong-Macao Greater Bay Area, SE China: Implications for geothermal resource exploration and seismic hazard assessment

Geothermal resources and seismic activity are two related earth science frontiers that are of great significance to socioeconomic development. The Guangdong-Hong Kong-Macao Greater Bay Area (GBA) in southeastern China is a geothermal resource-rich and seismically active region. Crustal stress information is crucial for identifying prospective hidden geothermal fields and assessing seismic hazards. However, the characteristics of crustal stress in the GBA region remain unclear. In this study, we construct a high-resolution three-dimensional (3D) geomechanical model of the GBA region with complex fault geometries and obtain the 3D stress state. The results show that the GBA region is subject to a laterally variable crustal stress field. The maximum horizontal stress (S_H) is oriented predominantly NW-SE in the east of the study area and rotates to nearly N-S in the west. The shallow crust is dominated by a transpressional stress regime, while the deeper part exhibits transtension. Detailed stress analyses on typical individual faults show that the NW-trending faults commonly have low normal stresses and high dilation tendencies, thus favoring geothermal fluid circulation. In contrast, the ENE-/NE-trending faults, at high angles to the S_H orientation, tend to act as barriers to fluid flow in the shallow crust and accumulate high strain energy, making them conducive to the generation of strong earthquakes. We propose a comprehensive conceptual model to illustrate the genetic mechanism of geothermal resources and strong earthquakes. This study is intended to promote the exploration of geothermal resources and support the seismic hazard assessment in the GBA region.