Present-day stress tensor is characterized in southeastern Korean Peninsula using shallow geotechnical in situ stress data to understand the regional contemporary stress state and its relationship to the population of faults. The in situ stress data show an ENE-WSW to NE-SW maximum compression direction, which is in accord with the contemporary earthquake focal mechanism solutions, as well as the first order pattern of tectonic stress direction in the eastern Eurasian plate. The current stress tensor exhibits a heterogeneity in its orientations and magnitudes, possibly caused by the influence of faults. The horizontal principal stresses normalized by vertical stress vary spatially. The magnitude of stress field appears to be inversely correlated with the density of regional scale faults, suggesting that a stress relief due to faulting may be one of the major factors that contribute to low stress magnitudes.
It is knownthat structural elements such as active faults and joints influence in situ stress conditions locally (Barton & Zoback 1994, Sassi & Faure 1997, among others). In order to verify the likelihood of correlation between in situ stress states and regional scale faults in a relatively wide region, we analyze stress tensors in southeastern Korea. We use stress data determined through shallow (100–320 m) borehole in situ stress measurements such as the hydraulic fracturing and the overcoring methods. The in situ stress measurement methods provide a complete in situ stress tensor (magnitudes and orientations) at a point. Although the measurements are normally constrained within shallow depths, they are the only methods that can be utilized for stress tensor analysis in a relatively wide region, because of the abundance of data. In order to verify the reliability of the results, we also compare the results with earthquake focal mechanism solutions.
