包代河断裂古地震初步研究

PRELIMINARY RESEARCH ON PALEOEARTHQUAKES OF THE BAODAIHE FAULT

包代河断裂是 1 954年山丹 7 级地震的主破裂带 ,为右旋正倾滑断裂 ,长约 4 .5km .经开挖探槽在该断裂上揭露出三次古地震事件 ,分别发生在距今约 31 2 0± 2 50a后 ;2 50 0± 1 90a左右 ;2 1 50± 1 70a之后 ,古地震重复间隔约 350～ 70 0年 .

The Baodaihe fault is the main seismic rupture zone of 1954 Shandan earthquake(M =71/4), which shows right lateral strike slip movement with a small portion of dip slip component. The fault is about 4.5 km long. For the first time ,three paleoearthquake events can be identified in the trench cross the Baodaihe fault. According to the 14 C and TL age date of the strata in the trench, the first event occurred later than 3 120 ±250 a B.P., the second one took place approximately 2 500±1 70 a B.P., and the third one occurred later than 2 150 ±170 a B.P., the recurrence interral of great earthquake along the fault is approximately 350～700 years.