酒西盆地白杨河断裂古地震特征研究  

Paleoearthquake Characteristics along the Baiyanghe Fault in Jiuxi Basin

作　　者：刘兴旺[1,2] 袁道阳 苏琦[3] 苏鹤军[1,2] LIU Xingwang;YUAN Daoyang;SU Qi;SU Hejun(Lanzhou Institute of Seismology,China Earthquake Administration,Lanzhou 730000,Gansu,China;Lanzhou National Observatory of Geophysics,Lanzhou 730000,Gansu,China;School of Earth Science and Engineering,Nanjing University,Nanjing 210046,Jiangsu,China)

机构地区：[1]中国地震局兰州地震研究所,甘肃兰州730000 [2]兰州地球物理国家野外科学观测研究站,甘肃兰州730000 [3]南京大学地球科学与工程学院,江苏南京210046

出　　处：《地震工程学报》2020年第1期90-97,共8页China Earthquake Engineering Journal

基　　金：国家自然科学基金青年基金(41402186)

摘　　要：白杨河断裂是酒西盆地内部一条重要的活动断裂,断裂长约25 km,整体走向近EW,倾向N,倾角约25°。以往的研究认为白杨河断裂为一条全新世活动的隐伏断裂,其持续的活动造成了上覆阶地变形,形成白杨河背斜。通过卫星影像解译和野外实地考察,在断裂西段和中段发现连续发育的低断层陡坎,表明断裂活动已至地表。古地震探槽揭露白杨河断裂全新世以来至少发生过2次地震事件,年代分别为距今(8.7±0.6)ka和(3.9±0.5)ka,每次地震事件的垂直断距都在约0.6 m,利用经验公式,估算震级约为6.8级。The Jiuxi basin,located at the westernmost part of the Hexi Corridor,is a Cenozoic depression basin bounded by multiple groups of active faults.Many Holocene active faults have been developed in the basin.These faults played an important role in the coordinated absorption of the eastward expansion of the Qilian Mountains and the left lateral slip rate of the Altyn Tagh fault.The basin has a complex structure,and there is a tectonic setting for the occurrence of moderate-strong earthquakes.In recent years,many Holocene activities have been found in the inner and surrounding areas of the Jiuxi basin.Therefore,its seismic risk cannot be ignored.The Baiyanghe fault,with a length of 25 km and almost E-W trending,is located in the middle part of the Jiuxi Basin.The fault dips to the north with a dip angle about 25°.In a former research,the fault was deemed as a buried fault.Its continuous activity resulted in the deformation of the overlying terrace and the formation of the Baiyanghe anticline.According to the satellite image interpretation and field geological investigation,we found a continuous development of a low fault scarp in the west and middle segments of the fault,indicating that the fault is not entirely a buried fault,and some parts of the fault have reached the surface and become a broken surface fault.Two trenches excavated across the fault scarp revealed that at least two paleoearthquake events,aged about(8.7±0.6)ka and(3.9±0.5)ka,respectively,have occurred along the Baiyanghe fault since the Holocene.The vertical dislocation of the events was about 0.6 m.Using an empirical formula,we inferred that the magnitude of the earthquake was about 6.8.

关 键 词：白杨河断裂 活动断裂 古地震 全新世 

分 类 号：P315.2[天文地球—地震学]