Hydropower dams associated with a large reservoir, a key renewable, face challenges like reservoir-triggered seismicity (RTS). Here, rock samples show 6.3 %–14.7 % porosity and a maximum permeability of 0.0098 mD. A 136 m reservoir rise causes a 0.61 MPa pore pressure increase. Vertical stress rises by 0.75 MPa, and horizontal stress falls by 0.48 MPa, which leads to fault destabilization, causing RTS. These facts urge the adoption of sustainable energy strategies and future dam development.

Transform faults are conservative plate boundaries where no material is added or destroyed. Oceanic fracture zones are their inactive remnants and record tectonic processes that formed oceanic crust. In this study, we combine high-resolution data sets along fracture zones in the Gulf of Guinea to demonstrate that their formation is characterized by increased metamorphic conditions. This is in line with previous studies that describe the non-conservative character of transform faults.