怒江断裂带邦达断裂中段全新世活动证据及其古地震记录

活动断裂带常是大地震的发震构造,并诱发地质灾害,产生黏滑位错和蠕滑变形,并形成断裂破碎带,进而对城市和工程安全直接造成威胁。因此,厘定活动断裂的空间几何展布、活动性对工程地质研究和防灾减灾具有重要的指导意义。通过遥感解译、错断地貌、槽探和14C测年,对怒江断裂带邦达断裂中段的发育分布特征与活动性进行了调查研究。结果表明：邦达断裂中段在1457±51 a BP/1598±47 a BP 发生过古地震事件,为引发中强地震的全新世活动断裂。断裂活动主要受控于川滇菱形块体的南向逃逸挤出和印度板块NEE向直接挤压作用,表现为走滑兼有逆冲分量的高角度活动断裂。该研究为了解怒江断裂带邦达断裂中段活动性和工程抗震设防提供了基础资料。     

Distribution characteristics and its influencing factors of active layer thickness in Tanggula area on the Qinghai-Tibet Plateau北大核心CSCD

多年冻土区活动层的冻融过程显著影响地-气间的水热交换、地表水文过程、冰缘地貌演变及寒区工程建设。活动层厚度的空间分异规律及其空间分布的准确模拟计算是冻土学研究的基础和核心问题之一。作为青藏高原中部东西走向最大的山脉和青藏高原多年冻土的主要分布区,唐古拉地区是青藏高原南部湿润区与北部干旱区的过渡区,该地区的活动层厚度空间分异规律研究对于揭示青藏高原多年冻土区活动层厚度整体空间分布规律具有重要意义。利用唐古拉地区南、北坡两个区域野外实测活动层厚度分布数据,分析了该区域活动层厚度的空间分异特征及其主要影响因素。结果表明,活动层厚度分布的突出特点是空间分异巨大,最小值仅为1.2 m,最大值达到5.6 m。以不同植被类型区活动层的平均厚度为对比标准,其分布特征为：沼泽草甸<高寒草甸<高寒荒漠<高寒草原,高寒草原的平均活动层厚度最大。对比南、北坡,南坡活动层厚度普遍大于北坡。Stefan方程的计算结果表明,活动层厚度的变化速率随土壤含水率的变化最大,其次为土壤热导率,而随地表融化指数的变化最小。实测土壤含水率、探坑数据及地表融化指数与活动层厚度分布关系表明,影响活动层厚度空间分异的最为敏感的因素为土壤含水率,其次为土壤热导率,地表融化指数的敏感性最小。     

碰撞带热结构与碰撞成矿系统

造山带热结构对大陆碰撞带的形态大小、构造式样、岩浆活动和变质作用具有重要控制作用。然而,热结构对碰撞成矿作用的控制还不清楚。本文概述比利牛斯、阿尔卑斯、加里东、扎格罗斯、青藏高原和华力西等全球主要碰撞带的热结构与成矿系统发育特征,对比各个造山带内不同矿床类型成矿温度变化,探讨热结构对碰撞成矿的控制作用。研究表明,碰撞带主要发育盆地流体有关的密西西比河谷型铅锌矿床、变质流体有关的造山型金矿床和岩浆热液有关矿床(斑岩铜矿床、云英岩型钨锡矿床和岩浆热液有关的铌钽锂铍矿床等)。其中,前两者在大多数碰撞带内均有发育,代表了大陆碰撞成矿作用的基本类型。这些矿床的成矿温度在热碰撞带比较高而在冷碰撞带则偏低。岩浆热液有关矿床一般只出现在比较热的碰撞带内,这些热碰撞带的温度压力条件有很大区域在湿固相线以内,热扰动能够造就地壳发生部分熔融形成含矿岩浆。     

中国东北地壳结构的地震层析成像

中国东北地区自晚古生代晚期以来,受古亚洲洋、蒙古—鄂霍茨克洋、太平洋构造域的叠加作用,壳幔结构极为复杂。本文收集中国东北地区国家地震台网接收的100 980个P波和91 030个S波到时数据,采用地震走时层析成像方法获得了该地区地壳P波和S波速度结构,进而获得了泊松比结构,用以探讨复杂的地壳结构。成像结果显示：中国东北地区地壳地震波速度结构呈明显的横向不均匀性,不同构造单元和构造单元内部都存在不同程度的不均匀性。松辽盆地整体上浅层地壳以低速异常为主,尤其是S波速度,但部分区域分辨率较低,中下地壳存在较大范围高速异常,推测与太平洋俯冲、后撤导致的岩石圈拆沉和热物质上涌等动力学过程有关;北部的大兴安岭重力梯级带和长白山一线主要表现为低速异常,表明具有大范围的岩浆作用,广泛岩浆作用为固体矿产资源的形成提供热源或物源;长白山、五大连池等近代活动的火山下方部分地壳区域均表现了较强低地震波速度和高泊松比异常结构特征,表明仍存在活动的可能。     

云南小江断裂东支活动性分析及工程场地稳定性评价

小江断裂延伸长、次生断裂交错分布多,使得区域内重大工程难以避免活动断裂带的影响,因此活动断裂的活动强弱以及场地稳定性是区域重大工程建设面临的主要工程稳定性问题。为了查清活动断裂对公路工程场地的影响,笔者等基于小江断裂地质构造背景,充分利用既有研究成果资料,重点研究区域构造环境和断裂特征,通过地质调绘、物理探测、年代学测试,结合对前人资料的系统梳理,计算分析了小江断裂中段东支活动速率,初步判定断裂活动程度;并综合考虑断裂活动性、地震烈度、岩体特性等因素,对工程场地稳定性进行分级。结果表明,小江断裂东支平均水平位移速率为6.6 mm/a,判定为强活动断裂,区域工程场地稳定性划分为极不稳定区;认为强烈活动性断裂两侧各10 km区域内对工程的影响最为严重,为公路工程场地选址和抗震设计提供了理论和数据支持。     

青藏高原东北缘活动构造与共和盆地高温热异常形成机制

构造作用是影响地球深部内热向地表传输和热能再分配过程的关键因素之一。青藏高原东北缘共和盆地发现高温地热资源,其热源成因机制一直是研究焦点。为理解构造作用对地热资源分布的控制过程,本文选取共和盆地高温地热异常区,分析边界断裂构造性质、活动期次、演化历程,结合钻井、大地电磁和背景噪声成像地球物理异常特征,提出新生代构造演化和地热异常形成的耦合关系。认为:1)青藏高原东北缘共和盆地及周缘变形区形成于昆仑断裂和海源断裂大型活动左旋走滑作用的滑动消减带;2)共和盆地新生代以来经历中新世(12–6 Ma)旋转泛湖盆凹陷、上新世—第四纪(6–3 Ma)盆内张扭变形两期主要演化阶段;3)共和盆地上地壳发育的与高温相关的地球物理低速-高导异常层(Vs<3.2km/s,R<10Ω·m)是主导热源;4)上新世持续左旋走滑变形导致的岩石圈隆起变形是深部热能向浅层传输的主要动力学机制,浅部热能聚集成热过程至少延续到了3Ma;5)预测青藏高原东北缘与共和盆地具有类似构造演化性质的次生盆地具有高温地热资源发育的条件。     

青藏工程走廊活动层厚度预测模型与分布特征研究

为探究青藏工程走廊沿线多年冻土区活动层厚度分布情况,结合青藏公路、青藏铁路沿线300个钻孔点的活动层厚度监测数据,基于年平均地表温度、平均植被指数、等效纬度、纬度、高程和含冰量等参数建立了活动层厚度的经验公式、随机森林和径向基函数（radial basis function, RBF）神经网络预测模型。各预测模型结果表明,活动层厚度与各预测因子间具有极强的非线性关系;RBF神经网络预测模型具有最高的预测精确度,拟合优度R²达到0.84。运用RBF神经网络预测模型和高精度遥感数据绘制活动层厚度分布图,分布图显示研究区内活动层厚度主要为2~4 m,总面积为5 468.3 km²,面积占比为47.27%,主要分布于楚玛尔平原至北麓河盆地和唐古拉山区南部至头二九山区;活动层厚度大于4 m次之,总面积为3 382.3 km²,面积占比为29.24%,整体分布偏向南部地区,主要分布于布曲河谷地至头二九山区。并对研究区活动层厚度与含冰量、地温关系进行了研究,结果表明活动层厚度随含冰量增加而减小、随地温升高而增加。     

Acceptance of the international compensation regime for tanker oil pollution – And its implications for China

The international compensation regime for tanker oil pollution has been successful in providing adequate and prompt compensation to pollution victims in its member states. Nevertheless, the attitudes of different countries toward acceptance of this regime have varied considerably. This paper aims to explain three main factors in the acceptance of the regime, including: (1) The level of economic development; (2) the risk of exposure to tanker oil spills; and (3) the financial burden associated with adherence to the International Oil Pollution Compensation Fund (IOPC). Using both fuzzy-set Qualitative Comparative Analysis and an Ordered Probit model, this study found two patterns causing upper-middle and high income countries to have a high acceptance level: (a) Those facing a medium risk of oil spills and having a low financial burden; and (b) those facing a high risk of oil spills. The study reveals that, for a country with a high risk of exposure to tanker oil spills, such as China, with its improvement in economic status it is far better for it to join the IOPC Fund, so as to provide better protection both for potential pollution victims and for the marine environment. The results of this study can also be applied to other countries that are considering whether or not to accept the international compensation regime for tanker oil pollution.     

Evidence of a phase shift to Epizoanthus gabrieli Carlgreen, 1951 (Order Zoanthidea) and loss of coral cover on reefs in the Southwest Atlantic

There is at present a ‘coral reef crisis’; one of the more drastic consequences of this is a phase shift, in which reef‐building corals are replaced by non‐reef building benthos such as macroalgae and soft corals. Previous studies have principally focused on the shift to macroalgae. Our goal was to investigate whether the dominance of the zoanthid Epizoanthus gabrieli on some reefs of Todos os Santos Bay, Brazil, represented a non‐algal phase shift. In 2003, we identified a high cover of this species on two reefs (52% and 70%), but only in 2007 was it possible to confirm a reduction in coral cover. This dominance has persisted for over 9 years, characterizing a true phase shift. This loss of coral cover may be a result of anthropogenic disturbances within the bay; however, given the large number of human impacts, further studies are needed to identify specific causes of this shift. Although there are some reports of phase shift involving species pertaining to the Class Anthozoa, this is the first report of this phenomenon involving the order Zoanthidea.     

Magnetic field and radius of the innermost stable circular orbit near super‐massive black holes in active galactic nuclei

Magnetic fields in an accretion disk around the central black hole can modify the size of the innermost stable circular orbit (ISCO) and can produce a difference to the classical Novikov‐Thorne radius. We estimated the ISCO magnetic field strength from the polarimetric observations of the accretion‐disk radiation. This estimate is obtained taking into account the effect of the Faraday rotation of the polarization plane at the distance of the mean free path of photons between successive electron scattering events. We present the new method for estimating the ISCO radius in the accretion disk, i.e. in the nearest vicinity of a central black hole. Our estimates confirmed the Frolov, Shoom & Tzounis (2014) and Ranea‐Sandoval & Garcia (2015) conclusion that the magnetic field in the accretion disk decreases the size of the innermost stable circular orbit. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)