龙首山北缘断裂带古地震初步探讨  

Preliminary Research on the Paleoseismicity along the North-edge Fault Zone in Longshoushan

作　　者：董治平[1] 程建武[1] 郑卫平[1] 刘洪春[1] 郭桂红 

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州730000 [2]西部灾害与环境力学教育部重点实验室,兰州大学土木工程与力学学院,甘肃兰州730000

出　　处：《西北地震学报》2013年第B12期46-50,84,共6页Northwestern Seismological Journal

基　　金：甘肃省地震局地震科技发展基金(2012M06);甘肃省自然科学基金(0710RJZA070)

摘　　要：龙首山北缘断裂带是潮水盆地与龙首山地的地貌分界线，展布于龙首山隆起的北麓。前期曾在龙首山北缘断裂带东段的白家嘴、中段包代河、西段斜坡山开挖了三个探槽，均揭露出多期古地震。本文通过三个探槽古地震事件的对比分析认为，龙首山北缘断裂带第1次古地震（11ka）到最后1次古地震（1．6ka）间隔9．4ka，约1万年时间里有6次古地震发生。如果取算术平均（9．4ka／6—1．57ka），则每隔1500年左右，龙首山北缘断裂带就有一次强地震事件，即古地震平均重复间隔约1．57ka。这和其它各大断裂带得出的古地震优势重现周期（1～2ka）并不矛盾。①5ka年以前龙首山北缘断裂带仅有2次古地震事件，重复间隔5．3ka，明显偏长，可能有古地震的遗漏问题；②5ka年以后该断裂地震活动明显丛集，最短间隔0．7ka，最长间隔1．5ka，平均重复间隔约0．8ka。无论是最短、最长或平均重复间隔，均与山丹一张掖地区历史地震的最长重复间隔0．79ka接近。The north-edge fault zone of the Longshoushan fault is the relief boundary between the Chaoshui basin and the mountainous region of Longshoushan. According to the result of previous studies, three trenches have been studied in the Baijiazui trench at the eastern section of the fault, Baodiahe trench at the middle section and Xieposhan trench at the west, which reveal several e- vents to us. On the basis of comparative analysis of the three trenches, this paper shows that since Holocene, six events had occurred in the north-edge fault zone of the Longshoushan in the 11 ka; the average of the recurrence interval is about 1.57 ka. It is compatible with the predomi- nance recurrence interval in other fault zones, which is 1-2 ka. （a） Some paleoearthquakes may be missed there as only two events occurred before 5 ka B. P and the recurrence interval was obvi- ously more than 1-2 ka. （b） The activities of paleoearthquakes obviously clustered. The maxi- mum of recurrence interval is 1.5 ka and the minimum is 0.7 ka, and the average is about 0.8 ka.All of these conclusions are close to maximum of recurrence interval of the historic earthquake （0. 79 ka） in the Shandan--Zhangye region.

关 键 词：龙首山北缘断裂带 古地震 全新世 探槽 

分 类 号：P315.2[天文地球—地震学]