摘要
南黄海辐射沙脊群中部黄沙洋潮流通道的浅层地震剖面揭示了3处典型海底滑坡,滑坡区域西南距如东大洋口34.5km,南距西太阳沙人工岛17.1km。潮流通道中段北侧,即蒋家沙南坡的滑坡规模较大,滑坡后壁下滑错断达15m,宽度超过300m;潮流通道中段南侧,即茄儿杆子沙北坡东西两处探测到的滑坡形态相似且距离接近,应为同一滑坡体,为中型等级。黄沙洋潮流通道近几十年沉积动力环境基本稳定,滑坡体各错断上部均无沉积物覆盖,故推断1984年5月21日南黄海Ms 6.2级地震是诱发这两个海底滑坡体的主要因素。该地震震中位于NW—SE向苏北—滨海断裂带和E—W向栟茶河断裂带的交叉区,上述两个滑坡发生于这两个断裂带近震中处,且前一个断裂带(该地震的主破裂面)上诱发的滑坡体规模较大。本区海底上部普遍发育潮汐环境下形成的砂泥互层沉积,下部为古河道砂质沉积,加之潮道边坡坡度相对较大,震动触使含水砂层运动,出现"液化现象",造成边坡失稳而诱发上部地层发生错断,导致潮流通道两侧沙脊边坡出现滑坡。近年来,江苏海岸开发加速,工程建设加快,潜在滑坡以及浅层气、软基等地质灾害在辐射沙脊群海域相对密集,探明与查清滑坡体空间分布与发展趋势,对保障海岸重大工程建设安全具重要意义。
Three typical submarine landslides have been found in the two shallow seismic profiles across the middle Huangshayang tidal channel in the central part of the radial sand ridge field(RSRF),South Yellow Sea(SYS),which is 34.5km northeastwards away from the Da-Yangkou,and 17.1km northwards away from the West Taiyangsha artificial island,Rudong County.The largest one is located on the northern side of the tidal channel,that is,on the southern slope of the Jiangjiasha sand ridge.The main scarp is up to 15 m high and more than 300 m wide.The other two are located on the southern side of the tidal channel or the northern slope of the Qie'erganzi sand ridge.These two landslides are quite close to each other,and show similar shape.They should be the same landslide on medium scale.The sedimentary dynamics in the Huangshayang tidal channel have been relatively stable in recent several decades,and there are hardly any sediments covering on the top of the displacement of the landslides,it could be deduced that they might be the records of the Ms 6.2earthquake happened in the SYS on May 21 th,1985.The epicenter of this earthquake was located at the intersection zone between the NW—SE trend Subei-Binhai fault zone and E—W trend Bencha River fault zone.As these two fault zones are close to the epicenter,two landslides were induced,and the scale of the one happened at the main fracture zone of this earthquake,that is the prior one,was much larger.The upper part of submarine sediments in the RSRF was mainly composed of sandy-silty interbedded deposits formed in tidal environments,and the lower part was mainly fluvial sand deposits.Meanwhile,the slopes of the channels were relatively steep.Shaking was easily to induce the water-bearing sands to move,even to flow because of liquefaction.The slope became instable,and the upper part of sedimentary strata began to break.Consequently,the landslides happened on the both sides of the tidal channel along the slopes of the sand ridges.In recent years,the exploitation speed of the Jiangsu coast along the SYS is vastly improving and the coastal engineering constructions are developing rapidly.Hazardous geological factors,such as potential landslides,shallow gas and soft foundation,distribute densely in the RSRF.Therefore,it is important to investigate the spatial and temporal distribution and to understand the development trends of these hazardous geological factors in the whole RSRF,in order to guarantee the safety of the coastal engineering constructions.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
2015年第5期77-85,共9页
Marine Geology & Quaternary Geology
基金
国家重大科学研究计划项目(2013CB956500)
国土资源部公益性行业科研专项(201011019)
国家海洋局公益性行业科研专项(201005006)
关键词
浅层地震剖面
海底滑坡
灾害地质
海底地震
砂层液化
南黄海
shallow seismic profile
submarine landslide
hazardous geological factor
submarine earthquake
sand deposit liquefaction
South Yellow Sea