Geodynamics of the Amirante Ridge and Trench Complex,Western Indian Ocean

The formation and evolution of the ～600 km long arcuate Amirante Ridge and Trench Complex (ARTC) is a significant geomorphic–structural feature in the Western Indian Ocean (WIO). The WIO contains evidence of at least two major magmatic episodes followed by continental rifting within the span of a little more than 20 million years. This involved the splitting of Madagascar from India at around 85 Ma and then separation between India and the Seychelles at 64–63 Ma as a possible consequence of two powerful volcanic eruptions from the Marion and Reunion hot spots, respectively. Formation and evolution of the ARTC represents this tumultuous period in the Indian Ocean, approximately between 85 and 60 Ma (Late Cretaceous–Early Tertiary).

We integrated geophysical, palaeomagnetical, and petrological data to examine three existing models that attempt to explain the formation of ARTC. In contrast, our study hints at several stages of extension and compression responsible for its formation. Our integrated data also suggest that the Carlsberg Ridge may have played a prominent role in the evolution of the ARTC that seems to have formed through a ridge-jump process after the conjugate spreading centres – Mascarene and Palitana ridges formed earlier during the India–Madagascar separation – ceased spreading because of violent eruption of the Reunion hot spot at around 65 Ma. The eruption disturbed the plumbing system of magma ascent, resulting in cessation of spreading along the conjugate spreading centres, forcing a ridge jump.

A collage of seismic refraction and reflection, free-air gravity, magnetic anomaly data, and Ar dating of rocks indicates that as the Carlsberg Ridge swept the Seychelles towards south, the crust between Madagascar and the Seychelles was increasingly compressed, with the abandoned northern Mascarene spreading centre absorbing the maximum stress. With continued compression, the western limb of the abandoned spreading ridge was thrust below the eastern limb to a limited degree. This partial subduction agrees with the gravity and seismic results. Our new study also accounts for the anomalous presence of 14 km-thick oceanic crust beneath the ARTC and its characteristic difference in petrology with other established subduction zones in the world.     

泥岩、砂岩石方开挖施工工法的创新与研究

通过新疆小山口水电站基础石方开挖工程实践,对当地泥岩和砂岩地质物理特性进行了深入研究,对其石方开挖工法进行了大胆创新,提出了纯机械法施工工法,分别从工程施工质量、进度、安全和成本等多个方面与传统的钻爆法进行比较,结果表明：新施工工法县有技术先进性和经济合理性,可以在今后的施工中使用和椎广。     

辽宁南部地区地壳剪切波分裂特征

利用辽宁区域数字地震台网2008-01?2018-12近场小地震波形资料,采用剪切波分裂(SAM)方法计算辽宁南部地区8个台站的快剪切波偏振方向和慢剪切波时间延迟,主要分析营口(YKO)台和盖县(GAX)台的剪切波分裂参数.分析结果表明:1)8个台站的快剪切波偏振优势方向以NE-NEE和NW两个方向为主,其中5个台站的...     

节理岩体动态破坏的SHPB相似材料试验研究

采用相似材料模型试验对不同节理倾角、节理贯通度、节理条数、载荷应变率、节理充填物厚度、节理充填物类型及试件长径比等7种工况下的节理岩体动态强度及破坏模式进行了分离式Hopkinson压杆(SHPB)试验研究。结果表明：节理岩体动态破坏模式及强度与节理构造形态密切相关。对于单节理岩体,其强度及破坏特征在很大程度上受节理倾角控制,节理倾角0°、90°试件动强度分别为完整试件的90%和71%,且其破坏形式均为张拉破坏;倾角60°试件动强度几乎为0;倾角30°、45°试件的动强度分别为完整试件的50%和18%,且其破坏以剪切破坏为主,兼有张拉破坏。中心1/4、1/2、4/5及全贯通节理试件的峰值强度分别为完整试件的95%、74% 、28%和17%,即随节理贯通度增加,试件动强度逐渐降低。含1~3条节理的试件动强度分别为完整试件的54%、23%和10%,即随节理条数增加,试件动强度随之有较大幅度降低,但节理条数的增加并没有改变其破坏模式。随着节理充填物厚度增加及节理充填物强度降低,试件强度依次递减,但破坏模式并没有改变。完整试件和节理试件的动强度均随着载荷应变率的增加而变大,且前者对载荷应变率的敏感性要远远高于后者,相应地试件的破坏模式也变得更加复杂。两类试件的动强度均随着试件长径比的增加先增大后减小,即存在一个最佳长径比。     

半合管钻探工艺在滇东南建水普雄稀土矿床勘查中的应用

滇东南建水普雄稀土矿是一个超大型风化壳离子吸附型稀土矿床,矿体赋存于长岭岗碱性岩体的全风化层和半风化层中。不同于花岗岩风化壳离子吸附型稀土矿,该矿品位高,厚度大,用一般的浅井和赣南钻等取样工程无法揭穿稀土矿体。本文介绍了建水普雄矿区用半合管钻探工艺和浅井工程在相邻位置的施工情况。根据相同的取样层位和样品长度,对比了矿体的品位变化情况,利用品位的相对误差和正负偏差进行了统计,结果表明,单一对应样品品位相对误差合格率为100%;品位<0.07%的正偏差样品占样品总数的78.57%,负偏差样品占样品总数的21.43%;品位≥0.07%的正偏差样品占样品总数的52.17%,负偏差样品占样品总数的47.83%,正负偏差在可控范围内;单工程平均品位相对误差合格率为100%。说明半合管钻探工艺能够有效地应用于风化壳离子吸附型稀土矿勘查,实现资源评价。     

泉州市规划区场地抗震性能与土地适宜性分区研究

在泉州市土地适宜性分区规划的编制过程中,建立了比较详细的钻孔资料数据库,给出了泉州规划区内不同土类的剪切波速按埋置深度进行修正的经验公式,并用这些经验公式计算了无实测波速资料的钻孔的等效剪切波速。文中按等效剪切波速和覆盖层厚度进行了场地类别的划分;采用震后残余应变和软化模量的思想和分层总和方法,综合考虑了软土厚度、埋深、地下水位对软土震陷量的影响,使软土震陷量计算结果更为合理。在充分考虑规划区内地形地貌、工程地质条件、场地类别、砂土液化、软土震陷、砂层及软弱土层的厚度分布、滑坡崩塌等对场地抗震性能影响的基础上,给出了更适合规划区的场地抗震性能评价标准,绘制了泉州场地抗震性能与土地适宜性分区图。     

Crust and upper mantle structure of East Asia from ambient noise and earthquake surface wave tomography

The complex tectonic background of East Asia makes it an ideal region for investigating the evolution of the continental lithosphere, for which high-resolution lithospheric structural models are essential. In this study, we measured Rayleigh-wave phase-velocity dispersion curves at periods of 10–120 s and group velocity dispersion curves at periods of 10–140 s using event records from more than 1,000 seismic stations in and around China. By jointly inverting new and previously published dispersion data from ambient noise and earthquakes, we developed a high-resolution shear-wave velocity model down to a depth of ～300 km beneath East Asia. Our model revealed heterogeneous lithospheric structures beneath East Asia, and allowed us to investigate the velocity structure of the entire lithosphere. We also derived crustal and lithospheric thickness models from the three-dimensional (3D) shear-wave model, revealing strong spatial heterogeneity and a general thinning trend of lithospheric thickness from west to east across the study region. Overall, our models reveal important lithospheric features beneath East Asia and provide a valuable baseline dataset for understanding continental-scale dynamics and evolution.     

反演瞬态瑞雷波频散曲线映射二维横波速度剖面

由于横波速度与岩土力学参数密切相关,因而是工程地质勘察中的关键参数。基于前人的思想,采用等厚薄层权重自适应迭代阻尼最小二乘法自动反演横波速度,提高横波速度的计算精度,进而映射二维横波速度剖面。用上述方法对某高速公路振冲压碾效果进行了无损检测试验,其结果与钻探和开挖验证一致。     

利用算子分裂迎风均衡格式解对流为主溶质运移问题

水污染模拟问题是水流问题与溶质运移问题的耦合问题.各种常见的数值解法在以对流为主溶质运移问题的求解中都会遇到困难,如用有限单元法或有限差分法时,会产生数值弥散与过量这两类误差.引入算子分裂迎风均衡格式法求解对流为主的水污染模拟问题,较好地克服了数值弥散和数值解出现振荡问题,该格式具有良好的稳定性、单调性及守恒性特点.     

Verification of Subseasonal-to-Seasonal Forecasts for Major Stratospheric Sudden Warmings in Northern Winter from 1998/99 to 2012/13

This study reports verification results of hindcast data of four systems in the subseasonal-to-seasonal(S2 S) prediction project for major stratospheric sudden warmings(MSSWs) in northern winter from 1998/99 to 2012/13. This report deals with average features across all MSSWs, and possible differences between two MSSW types(vortex displacement and split types). Results for the average features show that stratospheric forecast verifications, when further averaged among the four systems, are judge...