香山-天景山断裂带西段晚第四纪的特征滑动行为  

CHARACTERISTIC SLIP BEHAVIOR ANALYSIS OF THE WESTERN SEGMENT OF XIANGSHAN-TIANJINGSHAN FAULT ZONE SINCE LATE QUATERNARY

作　　者：李新男[1] 李传友[1] 

机构地区：[1]中国地震局地质研究所,活动构造与火山重点实验室,100029

出　　处：《地震地质》2015年第2期482-495,共14页Seismology and Geology

基　　金：中国地震局地质研究所基本科研业务专项(IGCEA1114);国家自然科学基金(41172322)共同资助

摘　　要：香山-天景山断裂带是青藏高原东北缘弧形构造带的重要组成部分,其东段曾发生1709年7级地震。虽然该断裂带西段缺乏历史地震记录,但在其各次级段上却保留了最新一次地震产生的较新鲜的地表破裂,以及沿其发生的大量冲沟同步左旋位错。为了确定西段晚第四纪以来的活动特征,通过野外实测与卫星解译获得了240个冲沟或山脊的左旋水平位移量,以及62个垂直位移量。将所测位移量值投影到断裂展布方向上,得到了水平和垂直位移量沿断裂的分布特征。对水平位移量做进一步的概率密度模拟和频率统计分析,结果显示水平位移量具有明显的分组性与倍数关系。6组水平位移量可能分别代表了6次古地震事件,而西段上开挖的探槽也揭露了相似的事件期次。其中,最新一次地震的同震水平位移量为3m,而其他几次较老地震产生的累积位移量分别为6m,9m,12m,16m和20m,每次地震的同震位移量近似。因此,推断香山-天景山断裂带西段晚第四纪以来的地震活动遵循特征滑动模型。The Xiangshan-Tianjingshan Fault zone is an integral part of the northeastern Tibet plateau fault system, and the 1709 earthquake of M 71/2 happened on the eastern segment of this fault. But there remains a fresh surface rupture produced by the latest earthquake and a lot of gullies left-laterally dislocated synchronously along the western segment of the Xiangshan-Tianjingshan Fault zone, which has no historical records. To determine the western segment＇s seismicity since the Late Quaternary, we measured 240 horizontal offsets of the gullies or ridges and 62 vertical offsets, combining with the field geologic investigation and satellite remote sensing decipherment. Characteristics of distribution of the horizontal and vertical offsets are obtained by projecting the measured displacements along the stretch of the fault. Through probability density simulation and frequency statistical analysis for the horizontal offsets, the results show that there are obvious grouping character and multiple relationships. The six groups of horizontal offsets may represent 6 paleoearthquakes, with a similar event sequence in the trench excavated on the western segment. The coseismic offset of the latest earthquake is 3m, and the cumulative offsets produced by other older earthquakes is 6m, 9m, 12m, 16m and 20m, respectively, and each earthquake has a similar coseismic offset. Therefore, we suppose that the activity on the western segment of the Xiangshan-Tianjingshan Fault zone obeys a characteristic slip model since Late Quaternary.

关 键 词：香山-天景山断裂带西段 位移量分布特征 古地震 特征滑动 

分 类 号：P315.2[天文地球—地震学]