岷江叠溪巨型古滑坡研究

四川省叠溪区域地质构造复杂、地震频发,沿岷江发育有大量古(老)滑坡及堵江灾害,特别是晚更新世晚期发生了一次大型滑坡堵江事件,形成了流域内规模最大的古堰塞湖—叠溪古堰塞湖,受到国内外学者的广泛关注.本文结合野外详细调查、无人机及LiDAR测绘、地貌分析、地球物探等多种技术手段,从"空—陆—地"三个视角剖析叠溪古滑坡,揭示古滑坡的地质、地貌和堆积体内部结构特征,确定了叠溪古滑坡的位置与规模,并讨论了其对区域地质环境的长期影响效应.研究结果表明,叠溪古滑坡为一巨型顺层岩质滑坡,源于岷江左岸的高陡岩壁,滑坡体方量达到1400～2000×106 m3.位于岷江右岸的平台上可见特殊的洼地凹陷,结合密度电阻率法对坡体内部结构的反演结果,发现叠溪古滑坡坝不仅完全堵塞岷江主河道,同时还阻碍了支沟流域,形成了沿汇流方向的低电阻率通道.叠溪古滑坡坝存活了约1.5万年,随后逐渐溃决,反映了构造活跃山区滑坡堵江链式灾害对山区地貌演化的长期作用.     

云南鲁甸M_S6.5地震红石岩滑坡稳定性的数值模拟

2014年8月3日鲁甸MS6.5地震触发了大量的滑坡崩塌,其中,位于鲁甸县李家山村和巧家县红石岩村交界处的牛栏江干流北岸的红石岩滑坡规模巨大,与此处位于左岸的红石岩古滑坡体的前缘部分一起堵塞了牛栏江而形成高达120m、体积达1 200×104m3的大型堰塞体。通过震后开展的野外实地调查,获得了红石岩滑坡发生处的地形地貌、地质构造、岩体结构及物质组成等资料。以这些第一手资料为基础,构建了红石岩滑坡的边坡模型,并应用边坡稳定性分析软件Geo Studio中Slope/W模块分别计算了红石岩滑坡体震前坡体安全系数和地震作用下的坡体安全系数。结果表明,红石岩滑坡体发生处的坡体安全系数在地震前为1.450,处于相对稳定状态,而鲁甸地震的地震动作用则使坡体的安全系数降低至0.962,直接导致红石岩坡体的失稳。文中进一步讨论了坡体滑动面的存在与否对坡体稳定性的影响:安全系数计算的结果表明,在中强地震作用下,先存滑动面的存在是导致大型滑坡形成的重要条件;对于高陡岩质边坡,如果没有先存滑动面,只可能形成浅表性滑坡。     

四川丹巴梭坡滑坡微震信号初探

与滑坡变形相关的微震称作滑坡震,反映了滑坡上不稳定区域对外界环境因素的响应,分析滑坡体微震事件的地震学性质能够为理解滑坡的动力学过程、进行滑坡稳定性分析以及灾害防治提供关键信息。放置在滑坡上的地震仪不但能记录到和滑坡变形相关的微震,可能还会记录到一些人类活动信号。滑坡上的人类活动产生的震动事件给滑坡震探测带来挑战。梭坡滑坡位于四川省丹巴县大渡河左岸猴子岩水库库尾,是丹巴县古碉群的集中分布区之一,近年来滑坡灾害频发,其稳定性对古碉群保护和水库蓄水位的选择均十分重要。为监测该滑坡体局部破裂产生的微震信号,2017年2月至3月在滑坡上布设了34台三分量短周期地震仪。基于信号到时和波形特征确定几类模板事件,采用滑动时窗互相关的方法检测微震事件,并对信噪比较高的事件进行定位。根据事件的位置和到时信息,估算出滑坡体东西部浅层沉积层面波速度结构存在一定差异,表明了滑坡浅层沉积层物质分布的横向不均匀。根据这些事件的发生时间和波形特征,认为除了滑坡震,梭坡滑坡上还存在燃放烟花造成的震动事件。     

强降雨作用下金场坝水库边坡稳定性分析与治理评价

以FLAC3D数值模拟计算为主要研究手段,基于结构动力学非线性有限元理论,结合某水库左岸边坡实例,对强降雨作用下滑坡体应力、位移、塑性区域进行研究,以及采用混合抗滑措施后的加固效果进行评价.结果表明:强降雨作用下,滑坡体内部主要以压应力为主,不存在拉应力;滑坡产生的最大竖向位移位于滑坡体的中下部;塑性区域面积存在集中现象贯穿滑坡体内部,滑坡处于不稳定状态.加固处理后,滑坡产生的最大竖向位移相比设抗滑装置前滑坡滑动位移量明显减小,塑性区域的面积减少,滑坡整体处于稳定状态,治理效果明显.     

Sarma法在四川云阳鸡扒子滑坡稳定性评价中的应用

云阳宝塔滑坡区先后发生了多次滑坡 ,其中鸡扒子滑坡是最近的 1次 ,新滑坡是在旧滑坡的基础上沿旧滑坡面的部分复活。根据对该滑坡体几何形态、物质成分与结构特征及水文地质特征的考察 ,初步认为 ,降水入渗与排水不畅引起的滑坡体内孔隙水压力上升是导致鸡扒子滑坡破坏的主导因素。文中根据极限平衡理论 ,运用VC + +语言编制了Sarma法的计算程序 ,对三峡水库蓄水后鸡扒子滑坡是否可能再次发生滑坡进行了评价 ,指出在滑坡体排水率为 5 0 %与三峡水库水位达 14 5m时为滑坡稳定与否的临界值。通过调整影响滑坡稳定性的主要参数的取值 ,对影响滑坡稳定性的因素进行了动态敏感性分析 ,指出降水入渗、长江水位、滑坡体的排水状况是影响滑坡稳定性的决定因素 ,三峡水库蓄水前应针对此采取相应的工程防治措施 ,才能保证水库蓄水后鸡扒子滑坡不再发生滑     

黄土地震古/老滑坡原始地形恢复方法研究

黄土地震古/老滑坡原始地形恢复是开展黄土地震古/老滑坡研究的基础。以宁夏回族自治区固原市西吉县平峰乡三合村潘沟组1号滑坡为例,利用卫星遥感解译和野外调查等技术和方法采集滑坡现今地形资料数据;并基于滑坡滑动前后滑坡体体积相等的原则,以MATLAB软件为平台,利用三维曲面插值技术恢复滑坡的原始地形,恢复后的滑坡原始地形斜坡坡面形态整体呈外凸型,坡度分布范围在12°～15°间;最后,利用黄土地貌单元的坡度分布范围和滑坡稳定性计算论证恢复结果的合理性和可行性。文章研究成果可为缺乏滑动前地形资料的黄土地震古/老滑坡原始地形的恢复提供新方法,对黄土地震古/老滑坡的研究具有重要的理论意义和工程应用价值。     

四川省理县西山村滑坡运动变形过程中的微震研究

西山村滑坡位于地震活动性剧烈的龙门山地区,这个区域有大量的滑坡在汶川地震中被触发,此后西山村滑坡发生持续变形.为了监测该滑坡体的运移和局部破裂产生的微弱的地震信号,由微震事件获取滑坡滑动和变形模式,2015年八月底至十一月底,我们在滑坡上布置了30套地震仪.首先通过信号到时和波形特征把滑坡上的微震信号从人类活动产生的信号和滑坡体以外的区域地震信号区分开来.然后以识别到的微震波形为模板,用滑动时窗互相关的方法匹配其他的微震事件.结果表明,96个微震事件能被30个台站都记录到.通过对这些事件的定位,我们发现大部分（80个）能被所有台站记录到的事件发生在滑坡的底部,其他的少部分（16个）发生在滑坡的顶部.这意味着有相当多的能量积聚在滑坡的顶部和底部,而滑坡的底部则更活跃.除此外,在滑坡的中部有较多更微弱的事件被周围的部分仪器记录到.基于这些微震事件的位置,我们发现四个辐射地震信号的不稳定区域和钻孔监测到的不稳定区域比较吻合.这些辐射地震信号的不稳定区域应该和滑坡体的运动和内部变形相关.由此表明,地震学方法也是监测滑坡的变形的有效手段,是现有监测手段的有力补充.     

山区剧动高速滑坡超前气浪的动力学机理

针对高速滑坡超前气浪灾害的动力学问题,建立了滑坡体沿坡面滑动的二维模型;采用动网格技术,数值仿真了高速滑坡超前冲击气浪的流场特征,分析了其形成的动力学机理。计算结果表明：随着滑坡体下滑速度增大,在滑坡体前缘上方和滑坡体后方出现的涡流逐渐加强,速度也逐渐变大;滑坡体下滑速度越大,在滑坡体正前方不同高度处的气浪速度越大,气浪所影响的距离越远,所造成的破坏也越大。在滑坡体正前方出现高压区,并且随着滑坡体下滑速度增大,滑坡体前方的压力变化也增大,压力的急剧增大也导致气浪速度变大。高速滑坡引发的,中击气浪在前方100m范围内产生12级以上的大风,破坏力极大。此研究将为超前气浪灾害的防治提供科学依据。     

土石混合滑坡体微动探测:以衡阳拜殿乡滑坡体为例

土石混合滑坡体地表地形复杂,土、石混杂堆积,结构松散,探测难度大,目前尚缺乏有效的物探手段.本文首次尝试将小台阵二维微动剖面探测技术应用于衡阳市拜殿乡的土石混合滑坡体探测.探测结果揭示,该滑坡体上部为砂质黏性土层,含块石较多;下为全风化花岗岩层,岩性较为均匀,块石含量少,其顶部为该滑坡体潜在的滑动面.滑动面在滑坡体后缘较陡、中部较为平缓,从而后缘的重力失稳、滑动风险更大.滑坡体的滑床（中-强风化花岗岩、微-未风化花岗岩）埋深在10 m以下,起伏变化较大,但岩体相对致密、完整,稳定性好,不易滑动.探测结果与钻探资料较为吻合,为评价滑坡体稳定性、设计合理的治理方案提供了地球物理依据.     

数字图像方法测量黑方台滑坡位移场

本文对典型的黄土滑坡进行研究,研究区域位于我国甘肃省永靖县盐锅峡的黑方台地区．具体方法为：首先对不同时序的黑方台滑坡监控视频截屏图片进行了亮度和对比度调整,以消除光照的影响,其次进行消除运动模糊处理;采用数字图像相关（DIC）方法对矫正后的图像进行整像素搜索和亚像素拟合,使滑动前后的滑坡体互相匹配,求出了滑坡上各点的位移方向和大小,从而得到了整体下滑时段滑坡上所有点的位移分布图及其发展变化图像．计算结果表明,在开始滑动的8 s之内,坡体做为一个整体滑动由慢到快,当总体滑动位移量达到0.3 m的量级以后,滑坡迅速解体分散下滑．用该方法计算滑坡地表位移场及其变化过程不仅成本低、操作简便,而且可以清晰地描绘滑坡的位移过程以及尺度．     

Contribution to the knowledge of the magmatic evolution by the study of the variation of the coefficient of viscosity

The determination of the coefficient of viscosity of eruptive products gives useful elements to the knowledge of possible variations of composition and physical conditions of the magmas.     

Pictorial Series of the Manifestations of the Dynamics of the Earth

Studia Geophysica et Geodaetica -     

Evolution of the Source of the Active Region of the Sun

Geomagnetism and Aeronomy - The magnetic evolution of the active region of the Sun at the level of the photosphere has been studied. Magnetic synoptic maps of the 2007 Kitt Peak Observatory were...     

Magnetic stratigraphy of the Ordovician in the lower reach of the Kotuy River: the age of the Bysy-Yuryakh stratum and the rate of geomagnetic reversals on the eve of the superchron

Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary.     

On the determination of the non-linearity of the gravimeter scale

Summary The results of two different methods of the determination of the non-linearity of the gravimeter scale are compared; the economy is discussed as well.     

Influence of the topography of the surface of the Earth on vertical sounding of the temperature profile

Atmospheric temperature and humidity fields as well as information on other meteorological parameters are nowadays retrieved from radiance measurements recorded by operational meteorological satellites. Up to now, the inversion procedures used only take into account crude information on the topography of the Earth’s surface. However, the applied radiative transfer codes have to consider the Earth’s surface as the lower boundary of the atmospheric model and, therefore, need a more precise mean elevation and a classification of the roughness of the Earth’s surface. The influence of the topography of the Earth surface on retrieved temperature profiles is studied by using a physico-statistical inversion method. An objective analysis is made of the more precise mean elevation and derivation of roughness parameters using a new high-resolution digital elevation model (DEM) with a resolution of 500 m×500 m. By means of a geomorphological process and a newly developed topography rejection test, areas with a high surface roughness are localized and singled out. The influence of topography on the retrieved temperature profiles is illustrated by case studies. Changes are found predominantly in areas with a high variation of topography. Using the new high-resolution DEM and the topography rejection test, the geographical position of the calculated temperature profiles tends to be shifted towards areas with a small vertical variation of topography. The mean elevation determined by the new elevation model better characterizes the area observed. Hence, the temperature profiles can be calculated down to lower atmospheric levels. Furthermore, a guess profile better describing the atmospheric situation is selected by the more precise elevation. In addition, the temperature profiles obtained near the coast are improved considerably by the more precise determination of the surface property ‘sea’ and ‘land,’ respectively. Integration of an independent physical information such as topography leads, on average, to a slight improvement of the results of the physico-statistical inversion procedure. In some cases, however, significant improvements have been achieved regarding the desired accuracy of temperature profiles of the order of 1 K. In future, the spatial resolution of new high-resolution sounding instrumentation on the next generation of operational meteorological satellites will be increased. To exploit the resolving power of this new instrumentation, the different variation of the topography of the Earth surface, especially in regions with a high variation of topography, can be taken into account more precisely by using a high-resolution DEM.     

The effect of the pollution of the ground layer of the atmosphere on the albedo

Summary A simple model is proposed suitable for studying the effect of the ground layer of the atmosphere, polluted by aerosol, on the albedo. This model is founded on solving the equation of transfer of radiative energy. The numerical results are discussed, particular attention being paid to the analysis of errors due to neglecting the multiple reflection of solar radiation on the aerosol particles. A method which would also include the multiple reflection is proposed, and the conditions under which the presence of the aerosol is responsible for an increase or decrease of the solar radiation balance on the Earth's surface, are analysed.     

On the solution of the reverse problem of geodesics with the help of the chord

Резюме Дается вывод формул для вычислений длины хорды, длины и азимутов нормаляных сечений и длины геодезической линии эллипсоида. Применяются тригонометрические функции данных величин и постоянные принятого ргфгргнц-эллипсоида, что является целесообразным при использовании вычислителQjных машин, особенно автоматов. Рабочие формулы рекомендуются в форме (8–11).

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Dedicated to Professor František Fiala on His 85th Birthday

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Address: Veveři 95, Brno.     

Evolutionary Changes in the Configuration of the Magnetic Field of the Solar Corona in the Epoch of the Minimum

Geomagnetism and Aeronomy - The evolution of the magnetic configuration in the solar corona is studied. The curvature of the K-corona helmets obtained from an analytical approximation of the...