Correlation between the deformation of mineral crystal structures and fault activity: A case study of the Yingxiu-Beichuan fault and the Milin fault

Abstract The build-up and occurrence of earthquakes are due to the accumulation and release of stress in fault zones. When subjected to tectonic extrusion stress, the crystal structure of the minerals within a fault zone will change. In this study, Raman spectroscopy analysis was conducted on the concurrently deposited quartz veins from Shenxigou, along the Yingxiu-Beichuan fault, and from Niyang River mouth, in the southern section of the Milin fault. The test results reveal a 3.29 cm−1 shift in the characteristic 464 cm−1 peak of the quartz in the veins along the fault plane of the Yingxiu-Beichuan fault, which was significantly lower than the shifts in the quartz peaks of the quartz on both sides of the vein. The 464 cm−1 peak shifts of the samples collected 10 m to the NW and 21 m to the SE of the fault plane were approximately 4.40 and 4.62 cm−1. In the veins from the Milin fault, considerable shifts of the 464 cm−1 quartz peaks occurred at the fault plane and to both sides within 5.5 m of the fault plane. No significant change in the 464 cm−1 Raman peak of quartz was observed for the samples 5–28 m to the SE of the fault plane. These results indicate that the tectonic extrusion stress accumulated more easily in proximity to the fault plane, resulting in significant changes in the crystals near the fault plane. We conclude that there is a correlation between the degree of change in the crystal structures of the minerals in thrust fault zones and fault activity, and such a correlation can provide a new method for studying the activity of thrust faults in areas with bedrock.