依兰-伊通断裂带尚志段晚全新世以来的强震复发间隔：来自古地震与历史文献的约束

LATE HOLOCENE AVERAGE RECURRENCE INTERVAL OF GREAT EARTHQUAKES OF SHANGZHI PART OF THE YILAN-YITONG FAULT ZONE,NE CHINA: CONSTRAINTS FROM PALEO-EARTHQUAKES AND HISTORICAL WRITTEN RECORDS

尽管依兰-伊通断裂中生代—早新生代以来的运动学和动力学研究在过去几十年中取得了显著进展和丰富成果,但受研究条件和手段所限,该断裂晚第四纪以来的强震复发间隔长期以来缺乏可靠的研究结果,致使无法科学认识其活动习性和地震危险性。基于高精度卫星影像解译和野外地质调查,发现该断裂尚志段存在至少长约25km的线性断层槽谷和陡坎。探槽开挖揭露出该断裂在全新世晚期发生EⅠ和EⅡ两期古地震事件,运动方式为走滑兼逆冲挤压,伴随明显的地层褶皱与缩短变形,累计垂直同震位移量约为(3.2±0.1)m。^(14)C测试年代结果约束古地震事件EⅠ发生于(440±30)^(180±30)a BP,事件EⅡ发生于(4 090±30)^(3 880±30)a BP。晚全新世以来的强震复发间隔约为(3 675±235)a。进一步的史料挖掘研究表明,EⅠ事件可能对应于朝鲜《日省录》记录的于公元1810年(清朝)发生在该地区的宁古塔历史地震,震级约7.0级。

Although the kinematics and mechanics of the Yilan-Yitong fault zone（ YYFZ） since the Mesozoic-early Cenozoic were studied very well in the past decades,few results about the average recurrence interval of great earthquakes in late Quaternary,which is the most important parameter for us to understand the active tectonics and potential seismic hazard of this crucial structure,were obtained because of its unfavorable work environments. Based on interpretations of high- resolution satellite images and detailed geologic and geomorphic mapping,we discovered that there exist linear fault scarp landforms and troughs in the Shangzhi part of YYFZ with a length of more than 25 km.Synthesized results of trenches excavation and differential GPS measurements of terrace surfaces indicate two paleo-events EⅠ and EⅡ occurring in Shangzhi part during the late Holocene,which resulted in ca.（ 3. 2± 0. 1） m accumulated vertical coseismic displacement with strike-slip motion accompanied by thrusting and shortening deformation.14 C samples dating suggests that event E Ⅰmight occur at（ 440± 30） and（ 180± 30） a BP and event EⅡ might happen between（ 4 090± 30） and（ 3 880±30） a BP,and the average recurrence interval of major earthquakes on the YYFZ is around（ 3 675± 235） a. Historical written records discovered from Korea show that the event E Ⅰ may correspond to the earthquake occurring in AD 1810（ Qing Dynasty in Chinese history） in Ningguta area with magnitude 7. 0.