Paleostress analysis of the Pohang-Ulsan area, Southeast Korea: tectonic sequence and timing of block rotation
Paleostress analysis of the Pohang-Ulsan area, Southeast Korea: tectonic sequence and timing of block rotation
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韩国浦项-蔚山地区古应力分析：构造序列和地块自转时间
DOI：
10.1007/bf02910169
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发表时间：
2001
影响因子：
1.2
通讯作者：
Gi
中科院分区：
文献类型：
--
作者：
Pom;Seok;Jae;Seung Ryeol Lee;Gi
为了重建韩国东南部梁山断裂带东段浦项-蔚山地区的构造序列，我们利用来自 29 个地点的断层滑移和张力裂缝数据分析了第三纪地层的古应力。从本研究分类的断层群中识别出大约十个间歇性断层事件。相对较年轻的断层事件的主应力轴与梁山断层西块的主应力轴有很好的相关性。然而，较旧的事件并非如此。研究区域每个地点的这些较旧事件的主应力轴的水平旋转使得两个区块之间的较旧主应力轴具有良好的相关性。因此，这可能使得建立浦项-蔚山地区的区域构造序列成为可能。由于相邻同轴事件的部分共存，10个断层事件按时间顺序可重新组合为5个主要构造事件：（1）NW-SE挤压和NE-SW伸展； (2) NE-SW压缩和NW-SE扩展； (3)NNE-SSW扩展和WNW-ESE压缩； (4)E-W压缩和N-S扩展； (5)NNW-SSE扩展和ENE-WSW压缩。该地点主应力轴旋转的时间主要与第三次构造事件、NNE-SSW 伸展或 WNW-ESE 挤压有关。研究区域发现的旋转似乎与区域规模的区块旋转有关。时间正好是日本西南地块与韩国东南部交汇的时刻（约 12 Ma）。春北地层中同沉积断层和砂岩脉的方向以及九龙浦地区周围NE-SW向脉岩的年代测定支持NE-SW挤压构造事件至少在中新世早中活跃。
In order to reconstruct the tectonic sequence in the Pohang-Ulsan area, eastern block of the Yangsan Fault, Southeast Korea, we analyzed the paleostresses for the Tertiary formations using fault-slip and tension gash data from 29 sites. Approximately ten episodic faulting events were recognized from fault populations classified from this study. Principal stress axes of the relatively younger faulting events are well correlated with those of the western block of the Yangsan Fault. However, this is not the case for the older events. A horizontal rotation for the principal stress axes of these older events at each site of the study area has produced a good correlation of the older principal stress axes between the two blocks. Consequently, this probably makes it possible to establish a regional tectonic sequence in the Pohang-Ulsan area. Because of the partial coexistence of neighboring coaxial events, the ten faulting events can be regrouped into five major tectonic events in a chronological order: (1) NW-SE compression and NE-SW extension; (2) NE-SW compression and NW-SE extension; (3) NNE-SSW extension and WNW-ESE compression; (4) E-W compression and N-S extension; and (5) NNW-SSE extension and ENE-WSW compression. Timing of the rotation of the principal stress axes at the sites is mainly related to the third tectonic event, NNE-SSW extension or WNW-ESE compression. The rotation found in the study area appears to have occurred in relation to a regional-scale block rotation. The timing falls on the moment when the SW Japanese Block converged into SE Korea (ca. 12 Ma). Orientations of syndepositional faults and sandstone dikes in the Chunbuk strata, and the dated ages of NE-SW trending dikes around the Guryongpo area support that the tectonic event with a NE-SW compression was active at least during the early-middle Miocene.