Controlling Factors on the Development and Connectivity of Fracture Network: An Example from the Baekildo Fault in the Goheung Area

The Baekildo fault, a dextral strike-slip fault developed in Baekil Island, Goheung-gun, controls the distribution of tuffaceous sandstone and lapilli tuff and shows a complex fracture system around it. In this study, we examined the spatial variation in the geometry and connectivity of the fracture system by using circular sampling and topological analysis based on a detailed fracture trace map. As a result, both intensity and connectivity of the fracture system are higher in tuffaceous sandstone than in lapilli tuff. Furthermore, the degree of the orientation dispersion, intensity, and average length of fracture sets vary depending on the along-strike variation in structural position in the tuffaceous sandstone. Notably, curved fractures abutting the fault at a high angle occur at a fault bend. Based on the detailed observation and analyses of the fracture system, we conclude as follows: (1) the high intensity of the fracture system in the tuffaceous sandstone is caused by the higher content of brittle minerals such as quartz and feldspar. (2) the connectivity of the fracture system gets higher with the increase in the diversity and average length of the fracture sets. Finally, (3) the fault bend with geometric irregularity is interpreted to concentrate and disturb the local stress leading to the curved fractures abutting the fault at a high angle. This contribution will provide important insight into various geologic and structural factors that control the development of fracture systems around faults.

Automated summary

This study investigated the spatial variation in geometry and connectivity of the fracture system near the Baekildo fault using circular sampling and topological analysis. The research found that the intensity and connectivity of the fracture system in tuffaceous sandstone are higher than in lapilli tuff, and the orientation dispersion, intensity, and average length of fracture sets vary depending on the along-strike position in the tuffaceous sandstone. Curved fractures abutting the fault at a high angle occur at fault bends, indicating geometric irregularities can concentrate stress and lead to curved fractures.