嘉鱼断裂西向延伸与第四系活动特征

Westward Extension and Quaternary Activity Characteristics of Jiayu Fault

嘉鱼断裂为已证实的隐伏断层。该断裂从洪湖老湾西南横切长江,沿近东西—北东东向延展,经嘉鱼县城东北马鞍山北缘向东延伸于斧头湖,长约40km,该断裂东端已有明显出露,而断裂尾部并没有明显出露。由于区内小尺度物探资料的缺乏,使得该断裂的走向和活动性都缺少相关证据。本文利用浅层地震反射结合折射层析成像方法,采用2m道间距接收人工地震波,利用多次覆盖技术和密集炮集折射记录,分别对数据进行反射处理和层析成像,获取了浅层地震反射剖面和高分辨率折射层析成像剖面,并参考相关区域地震安全性评价钻孔资料进行解译。综合研究结果表明:浅层地震反射和高分辨率折射联合应用可互补,尤其在外界干扰较为严重的区域,利用高分辨率折射层析成像可减少浅层地震反射对断层的误判。此外,研究结果证实了嘉鱼断裂的具体位置,其性质为北盘下降、南盘上升的正断层,且该断层错断了第四系沉积层。

Jiayu fault has been confirmed as a concealed fault,which is located in the northeast of Jiayu county.The fault is about 40 kilometers long.It stretches nearly EW-NEE,traverses the Yangtze River from the southwest of Honghu Laowan,passing the northern edge of Maan Mountain,and extends eastward to the Futou Lake.Although the eastern end of the fault is clearly exposed,the tail of the fault is not apparent.The lack of small scale geophysical data in the area leads to the lack of relevant evidence for the trend and activity of the fault.In this study,shallow seismic wave combined with refraction tomography was used to receive artificial seismic wave at 2 meters interval.Through the use of multiple coverage technique and dense spot collection refraction records,the data were separately reflected and tomographically imaged,and then the shallow seismic reflection profiles and high-resolution refractive tomography profiles were obtained,and the data is interpreted by referring to the relevant regional seismic safety evaluation drilling data..The comprehensive research results show that the application of shallow seismic reflection and high resolution refraction can be complementary,especially in the area where the external interference is serious,as the high-resolution seismic refraction tomography can reduce the chances of misjudgment of shallow seismic reflection.In addition,the study confirmed the specific location and its normal fault characteristics of Jiayu fault,which is characterized by the decline of the northern plate and the rise of the south plate,and the fault cut through the Quaternary sedimentary layer.