声波探测显示的渤海湾西部全新世断层活动  

The Holocene Active Fault in the Western Part of Bohai Gulf Showed by Acoustic Sounding

作　　者：赵根模[1] 赵国敏[1] 杨港生[1] 王大宏[1] 

机构地区：[1]天津地震局,天津市河西区友谊路19号300201

出　　处：《中国地震》2005年第2期139-146,共8页Earthquake Research in China

基　　金：天津市城市活断层工程项目。

摘　　要：本文展示了渤海湾西部浅地层声纳探测成果,讨论了渤海湾西部全新世和晚更新世上部地层划分、晚冰期与冰后期的沉积地层学特点及最新断裂活动的证据等。声波探测由于具有很高的分辨率和信号发射频度,可以获得高品质浅地层剖面,显示出沉积地层的结构与构造细节,如斜层理等三角洲沉积标志特征可清晰显示,水平层理不发育的黄土堆积特征也有显示。在声波剖面中地层界面的中断和弯折变形显示了最新断裂活动的证据,依据地层学资料,确定其年代距今仅为几千年,即全新世中期。这些断层的平面位置与基底或第三纪地质构造图中的断层位置一致,表明有些断层活动贯穿了更新世并延续到全新世,这些勘探成果对渤海西部断层活动性的鉴定具有重要意义。在声波剖面中还发现一些垂向小型结构构造,其成因不明,是否代表了某种地质事件,有待进一步深入研究。The authors showed and discussed the prospecting results of shallow stratum in the west of Bohai Gulf according to the original record of sonar exploration. The stratigraphic classification in the upper part of the Holocene and Late Pleistocene epoch is also discussed, and the characteristics of depositional topography of Late and Post-glacial, as well as the evidence of latest fault motions in this area. Because sonar exploration has high resolution and signal emission frequency, the shallow stratum profile with high quality can be obtained. The texture and structural detail of depositional topography, including the obvious marker of oblique bedding and delta deposit, and the accumulation characteristics of thick bed blocky loess that didn't develop in horizontal stratification.In the profile, the interruption and the bending deformation of stractal reflection surface gave evidence of latest fault motions. On the basis of stratigraphy, they were only several thousands of years, i.e. the faults moved during the early and middle period of Holocene epoch. The planimetric positions of these faults were consistent with the fault positions in the map of Tertiary geologic structure, which indicate that some fault motions were from the Pleistocene to Holocene epoch. In acoustic wave profile,some small vertical structures were also found. Their origins are not clear, perhaps they represent some geologic events. It remains to be studied in a deep going way.

关 键 词：声波 全新世 活断层 

分 类 号：P315[天文地球—地震学]