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.
出处
《西北地震学报》
CSCD
北大核心
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)
关键词
龙首山北缘断裂带
古地震
全新世
探槽
north-edge fault zone
Longshoushan fault
paleoearthquake
Holocene
trench
