A deep-seated E-W trending structural boundary indicated as extending across the Korean Peninsula at a latitude close to 40 deg N/Implications for defining areas with potential for strong earthquakes

摘要

A.The paper concludes that the deep-seated structural discontinuity which controls the Yinshan-Tianshan latitudinal belt in northern China (Fig. 6) continues eastward across the Korean Peninsula and the basement of the Sea of Japan. The main observations include: 1. A set of east-west trending fracture zones, revealed by a 3-D study in the eastern part of the Yinshan-Tianshan belt, extend as far east as the eastern coast of China (Cui & Wu, 1997; Cui et al. 2002, 2005 - Fig. 14) indicating that their continuation to Korean Peninsula can be expected. 2. A major change in geology, including fracture pattern, occurs on Korean Peninsula within latitudes 39 - 40 N, remarkably different from the geology to the north and south (Geological and Tectonic Maps of Korea on the scale of 1:1,000,000 - example in Fig. 9). 3. The Korean Peninsula, within latitudes 39 - 40 N, becomes narrower on both the western and eastern side, indicating preferential erosion and land destruction proceeding along a major east-west zone of tectonic weakness - Fig. 9. 4. The bathymetry of the Sea of Japan shows prominent east-west alignments in the center part of the basin, correlating with the latitudes of the major change in geology on the Korean Peninsula between latitudes 39 and 40 N (Fig. 11). 5. The bathymetry contours in the westernmost part of the Sea of Japan, adjoining the eastern part of Kore-an Peninsula between latitudes 39 and 40 N, give impression of remnants of a landmass after erosion and landdestruction (Fig. 11). 6. The Magnetic and Gravity Lineament Map of China provide additional support to the eastern continuation of lineaments from northern China to North Korea (Jiang & Ma, 1974,1991; Pei & Jiang, 1985) - Fig. 7. 7. Subsidence (intraplatform depression) on southern side of an E-W trending boundary shown on a genera-lized geological map of North Korea (Masaytis, ed., 1964) - Fig. 8. 8. East-west trending structural discontinuities (with offsets up to 50 km) extending transversely to the Japanese Island Arc, detected in the deep structure below Japan by intermediate and deep focus earthquakes (Carr, Stoiber & Drake, 1973) - Fig. 12. 9. Correlation with the Forty-north Fracture Zone proposed on a global scale by Kutina (1974) - Fig.1.