关键词: 北霍布逊湖, 阿木尼克山, 发震构造, 地表破裂, 历史地震

Abstract: The investigation of the seismogenic structure of historical strong earthquakes and the research on the genetic link between earthquakes and active faults is a basic seismic geology work. In particular, the investigation of seismic surface rupture zones and the study of seismogenic structures are extremely important for understanding the characteristics of their tectonic activities, The determination of the macro epicenter provides important evidence for the site selection for post-disaster reconstruction and avoidance. Due to the diversity of the rupture process in the focal area, the macro-epicenter and the micro-epicenter may not be uniform. As the magnitude increases, the larger the focal area of an earthquake, the more significant the gap between the macro-epicenter and the micro-epicenter. The northern margin of the Qaidam Basin is an earthquake-prone area, and there have been many earthquakes above 6.0 in history. Since the Delingha Ms 6.6 earthquake in 2003, two earthquakes of M 6.3 and 6.4 occurred in the northern margin of the Qaidam Basin in 2008 and 2009, which aroused the great attention of researchers. Research has formed new hot area. Through remote sensing interpretation, this paper finds that the linear characteristics of remote sensing images in the front of the Amunikeshan Mountain are obvious, and there are suspected surface ruptures of about 30km in length, and faults faulting alluvial fans and terraces of different periods. Through field geological surveys, it was discovered that there are developed fault ridges, fault grooves, seismic drum beams, and water system twists along the line, forming a surface rupture with a strike of N30°-40°W, a coseismic displacement of 2.3m, and a length of about 22km. Through the excavation of the trench, multiple faults were exposed in the section, forming the characteristics of multi-phase activities. Combined with surface relics, geological dating, micro-topography, etc, it is determined that the fault is mainly strike-slip, supplemented by thrust, and the profile is faulty to the surface, and activity has been obvious since the Late Quaternary. Based on empirical statistical relationship between magnitude and surface rupture, and the empirical relationship between strike slip fault and rupture length, the average magnitude required to produce 22km earthquake surface rupture is 6.79, and the average magnitude to form 2.3m coseismic displacement is 7.03. Combined with surface rupture, trench profile, geological dating, seismic geological disasters, empirical formula calculation and consulting historical earthquake catalogue, local chronicles and other documents, it is considered that the fracture zone is most likely formed by the M 6.8 earthquake on May 21, 1962, and its seismogenic fault is the Amunikeshan Mountain section of the fault on the north edge of Qaidam Basin. Because the residents in this area have no buildings (structures) as the basis for inquiring and investigating the earthquake intensity, it is impossible to draw the earthquake intensity map.

Key words: North Hobson Lake, Amunikeshan Mountain, Seismogenic structure, Surface rupture, Historical earthquake