CAJ | 학술논문

在青藏高原东边缘沿冕宁-宜宾进行了大地电磁探测研究,剖面西起康滇地轴,向东穿过大凉山地块,终止于四川盆地.利用带地形的NLCG(非线性共轭梯度)方法对资料进行了反演,得到沿剖面的二维电性结构.康滇地轴和大凉山地块地壳中存在向上拱起的高导层(HCL),顶面埋深为10～15 km,最浅处不足10 km,厚度大约15～25 km,最小电阻率小于10 Ωm.四川盆地中下地壳不存在高导层.和该剖面北侧的石棉-乐山剖面的地壳电性结构对比分析表明,高导层在南北方向上可能连续延伸,长度大于100 km.壳内高导层的高导电性与岩石的部分熔融有关,并可能含有百分之几的含盐流体,易于流动和变形.青藏高原东部地壳内的可流动层在向东或东南方向流动过程中,由于受到四川盆地的阻挡,转向南或南南东方向,大体沿着大凉山地块的走向.在东西方向,壳内高导层自川滇地块向东运动,穿过大凉山地块西边界的安宁河断裂和则木河断裂,在大凉山地块东部,向四川盆地深部倾俯.本文对于壳内可流动层的存在及其与青藏高原东边缘的变形和地震活动性的关系进行了探讨.
재청장고원동변연연면저-의빈진행료대지전자탐측연구,부면서기강전지축,향동천과대량산지괴,종지우사천분지.이용대지형적NLCG(비선성공액제도)방법대자료진행료반연,득도연부면적이유전성결구.강전지축화대량산지괴지각중존재향상공기적고도층(HCL),정면매심위10～15 km,최천처불족10 km,후도대약15～25 km,최소전조솔소우10 Ωm.사천분지중하지각불존재고도층.화해부면북측적석면-악산부면적지각전성결구대비분석표명,고도층재남북방향상가능련속연신,장도대우100 km.각내고도층적고도전성여암석적부분용융유관,병가능함유백분지궤적함염류체,역우류동화변형.청장고원동부지각내적가류동층재향동혹동남방향류동과정중,유우수도사천분지적조당,전향남혹남남동방향,대체연착대량산지괴적주향.재동서방향,각내고도층자천전지괴향동운동,천과대량산지괴서변계적안저하단렬화칙목하단렬,재대량산지괴동부,향사천분지심부경부.본문대우각내가류동층적존재급기여청장고원동변연적변형화지진활동성적관계진행료탐토.
A magnetotelluric sounding was carried out in the eastern edge of Tibetan plateau along Mianning-Yibin that starts from Kangdian Geo-axis (KDG) eastward crossing the Daliangshan block (DLSb) and ends in Sichuan basin block (SCb). A 2-D modeling with consideration of topography is used with the NLCG(Nonlinear conjugate gradient method) inversion. 2-D electrical structure model of crust and upper mantle was constructed. The upward arched high conductive layer (HCL) exists in the crust of both KDG and DLSb, but not in SCb. The HCL has a low resistivity of 3～10 Ωm and its top is about 10～15 km deep (the shallowest less than 10km) with a thickness about 15～25 km. The crustal electrical structure combined with that of Shimian-Leshan profile indicates that the HCL is continuous and extends for more than 100 km in south-north direction. The high conductivity of HCL may be related to partial melt of rocks and some quantity of salt fluid prone to deformation and flow. The flow of HCL under the pushing force from Tibetan plateau is directed to E and/or SE in eastern Tibet plateau, and then turns to S or SSE in DLSb due to the obstruction of Sichuan basin. In EW direction it crosses the west boundary of DLSb, Anninghe fault (ANHf) and Zemuhe fault (ZMHf). The crust flow layer in the eastern DLSb underthrusts eastward beneath SCb. The relationship between the flow of HCL and the tectonic deformation of the crust and the seismicity is analysed in the article.