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981.
金沙江流域区域地壳稳定性分区与定量评价 总被引:13,自引:3,他引:10
金沙江中、下游横穿横断山南北构造带, 新构造运动强烈, 地震活动频繁, 各种内动力地质灾害比较严重, 该区区域地壳稳定性相对较差。为服务于金沙江水电工程规划建设和减灾防灾的需要, 本文对金沙江流域沿江地区进行了地壳稳定性的评价与分区。文中依据地壳稳定性定量评价的原则和方法, 建立地质构造背景、地壳结构、地震以及地球物理等指标, 并将地壳稳定性划分为四个等级:稳定、基本稳定、次稳定和不稳定。然后按照上述系统进行地壳稳定性分区。最后, 综合各项研究资料来确定各区的定量评价指标, 并采用模糊数学方法对各区地壳稳定性进行综合评价。 相似文献
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G.?DrakatosEmail author N.?Voulgaris M.?Pirli N.?Melis B.?Karakostas 《Pure and Applied Geophysics》2005,162(1):37-51
— The three-dimensional crustal velocity structure in the area of the northwestern Greek mainland was determined by P-wave travel time inversion, applying a two-step tomography procedure. The data set consists of the travel-time residuals of 584 well located earthquakes. In order to improve the initial (reference) velocity model, before the inversion of travel times, the minimum 1-D model was determined. Several tests were conducted to estimate model stability and hypocenter uncertainties. The velocity distribution in the shallow layers (4 and 7 km) is strongly affected by the crustal thickness variation and the complex tectonics. A first, well-defined velocity discontinuity appears at a depth of 3–6 km, along the Hellenides Mountain chain. A second low velocity anomaly is detected at a depth of 9–12 km and may be connected with the Alpidic orogenesis. Another interesting feature appears beneath the Amvrakikos Gulf (horstgraben structure), where relatively low velocities (<6.0 km-1) appear to a depth of 20 km. Finally, a well-pronounced velocity boundary is found at a depth of 16 km. In general, low velocities are predominant along the Dinarides-Hellenides Mountain chain, rather typical for the upper crust.Acknowledgement. The authors thank the referees for their useful comments. Moreover, we would like to thank the General Secretariat for Research and Technology of Greece, for the partial support of this study. 相似文献
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C.?RiedelEmail author A.?Tryggvason T.?Dahm R.?Stefanson R.?B?dvarson G.?B.?Gudmundsson 《Journal of Seismology》2005,9(4):383-404
The tectonics of North Iceland is dominated by interaction of the Iceland hot spot and the mid-oceanic Kolbeinsey Ridge. Transform movement along the transition zone, often called Tjörnes Fracture Zone, and the seismicity it generates has been documented in the past. This study uses the seismicity data of the permanent South Iceland Lowland (SIL) network to quantify velocity structure from travel time inversion. The SIL seismic dataset is capable of illuminating parts of the region in a 3D seismic velocity inversion, primarily between 7 and 12 km depth, with less resolution elsewhere because of the sparse setup of the monitoring network. The problem has been analysed in 1, 2 and 3 dimensions and evaluated with 4 different inversion tools. The study reports a correlation of a seismic velocity anomaly in compressional wave velocity v p and shear wave velocity v s with the Husavik-Flatey fault and a further subsurface lineament stretching between the islands of Flatey and Grimsey. Finally, our results support a decrease of crustal thickness between the mainland and the island of Grimsey. 相似文献