全球五大板块的运动和形变──用卫星激光测距数据导出的站速度分析

根据德国卫星激光测距（ＳＬＲ）数据分析中心ＧＦＺ对１９８０年１月－１９９１年７月获取的ＳＬＲ观测数据处理后得到的４１个ＳＬＲ站的站速度，解算了北美、欧亚、太平洋、南美和澳大利亚板块之间的相对运动欧拉矢量，得到了第１个ＳＬＲ实测的板块运动模型ＳＰＭＭ１．与地学板块模型ＲＭ２和ＮＵＶＥＬ－１的比较指出，ＳＰＭＭ１大体上与地学模型一致，与ＮＵＶＥＬ－１更为接近；ＳＰＭＭ１的欧亚与北美板块相对运动欧拉极与ＮＵＶＥＬ－１的相应极很接近，但旋转速率明显偏小．还分析了各板块上ＳＬＲ站的局部形变特征．欧亚板块东部和西部存在１０－２０ｍｍ／ａ的相对运动；板块边界附近ＳＬＲ站的残差站速度基本上反映了该边界的构造形变特征．     

How valid are dynamic models of subduction and convection when plate motions are prescribed?

A detailed comparison between fully dynamic and kinematic plate formulations has been made in models of mantle convection. Plate velocity is computed self-consistently from fully dynamic plate models with temperature- and stress-dependent viscosity and preexisting mobile faults. In fully dynamic models, the flow is driven solely by internal buoyancy, while in kinematic models the flow is driven by a combination of the prescribed surface velocity and internal buoyancy. Only a temperature-dependent viscosity, close to the effective viscosity determined from the fully dynamic models, is used in the kinematic models. The two types of models give very similar temperature structures and slab evolutionary histories when the effective viscosity and surface velocity are nearly identical. In kinematic plate models, the additional work introduced by the prescribed velocity boundary condition is apparently dissipated within the lithosphere and has little influence on the convection under the lithosphere. In models with periodic lateral boundary conditions, slabs sink into the lower mantle at an oblique angle and this contrasts with the vertical sinking which occurs with reflecting boundary conditions. Models show that we can simulate fully dynamic models with kinematic models under either periodic boundary conditions or reflecting boundary conditions.     

全球板块运动及其对地球表面积变化的影响

利用几个典型全球板块相对运动模型的欧拉矢量,计算沿这些模型板块边界段的两两板块之间的相对运动速度,据此进一步计算一定时间尺度内这些板块边界段的面积变化. 并依据已有对相应各边界段性质-包括张性、压性及走滑性质的研究,设定组成各边界段的两个板块如何分别承担其面积变化的情况,得到各模型中每个板块的面积变化和全球表面积变化总量. 结果显示,在近100万年时间尺度内,地球南半球表面积增大、北半球表面积减小,地球总表面积变化为2.9万～3.6万km~2. 如果假设地球表面积的增量完全由体积膨胀引起,这将对应地球半径160～250 m的增加. 以NUVEL-1模型为例,全球14个板块中,非洲、 南美与南极三个板块的面积持续增大,其余11个板块的面积在逐步减小;不过,非洲、南美与南极这三个板块面积增大部分之和,能够完全抵消掉其余11板块面积之减小,而且使全球总体表面积增加. 本文进一步讨论了一些其他因素,例如俯冲带前进与后退等影响地球表面积变化的情况.     

An approximate method for determining the stability of two-scale flow in the mantle

Summary An approximate method of calculating the stability of two-dimensional convection rolls to cross-roll disturbances is evaluated by comparison with the results from exact analyses and good agreement is obtained. In particular, investigation of the second mode of the disturbance provides a qualitative estimate of the terms excluded in making the approximation. We conclude that this approximate method, sensibly used, gives a good indication of the stability of rolls to cross-roll disturbances.Application of this method is made to convection rolls heated partially or wholly from within, and to rolls in the presence of a longitudinal shear flow. The approximation indicates that, at high Rayleigh Numbers, growth rates are underestimated and so the amount of shear calculated to stabilise longitudinal rolls is a lower bound. Our results suggest that two-dimensional rolls are unlikely to be a stable flow pattern beneath even the fastest moving plates.     

帕米尔─西昆仑地震带强震活动的规律性特征

分析了帕米尔─西昆仑带的强震活动规律，指出该带强震活动在时间轴上可划为６个活动幕，在空间上可划为３个优势分布区域，地震活动水平呈西强东弱态势，并且存在强震从帕米尔向东南方向沿地震带作定向迁移规律，文章对此现象作出了物理解释．     

拟协调四节点板弯曲单元在薄板振动分析中的应用

本文以文〔１〕构造的拟协调板弯曲单元为基础，横向剪切应变假设中采用沿厚度二次分布，将其应用于薄板固有振动分析，求解前ｎ阶固有频率，结果表明该单元具有良好的数值特性。     

Influence of plate tectonics on the locations of geothermal fields

A number of geothermal fields explored so far in the circum-Pacific area occur along spreading ridges and subduction zones in areas of young tectonism and volcanism. A preliminary analysis, however, suggests that these geothermal fields are not situated along entire segments of plate boundaries but only at certain locations. In convergent zones these locations are (i) near the ends of plate boundary segments or (ii) in transverse zones that divide plates into several blocks 100–1000 km long. The locations of geothermal fields therefore appear to be influenced by plate geometry and correspond to lateral breaks in the continuity of the underthrusting plate.     

现代板块运动的测量和研究：地球物理方法

本文简要阐述了用地球物理手段测量和研究现代全球板块运动的理论和方法、现状和发展。结合最新地学板块运动模型ＮＵＶＥＬ－１,着重介绍了最近十几年来全球板块运动的研究进展,对目前存在的问题及未来的发展作了评述。     

我国周边地震活动对中国大陆地震的影响

分析了1900年以来中国大陆及中国周边地震资料，认为周边强震活跃必然导致大陆地震活跃，即中国大陆强震与周边强震活动具有一体性或滞后性；我国台湾和东北地区7级以上强震与华北地震活动有着较好的对应关系；日本8级以上强震的发生表明太平洋板块活动增强，受这一影响东北地区地震也将进一步活跃。     

地球内部岩石圈物理与动力学研究发展的新动向与今后的任务

本文通过对当代地球内部岩石圈物理与动力学发展的认识与分析，探讨了该领域的研究方向与今后的任务，并提出了相应的建议与对策     

南大西洋洋中脊板块构造运动过程:古地磁的约束

海底磁异常的形态与洋中脊两侧板块的微运动或变形密切相关.因此,这方面的研究可为确定板块运动的演化历史、小尺度的动力学过程以及洋中脊分段的机制等提供重要约束.本文对南大西洋一段洋中脊(31°S—34.5°S)两侧的磁异常的偏度进行了系统研究.结果表明研究区域内扩张方向并不总是垂直于洋中脊走向,并且研究区域不同剖面的扩张方向也不一致,具体表现为从北向南,平均扩张方向逐渐增加,依次为33.6°±5.3°、62.8°±13.0°以及94.3°±8.0°.这表明洋中脊的倾斜扩张机制具有复杂性,初步解释应该与转换断层的剪切应力增加有关.深部辉长岩层倾斜和扩张速率不对称性对海底磁异常偏度的影响值得深入研究.另外,由北向南确定的欧拉极向东移动,表明洋中脊两侧的板块在6.5 Ma期间存在剧烈形变.     

印度尼西亚巨震对华东地震形势的影响

根据印度板块和缅甸次板块运动GPS观测资料, 分析了印度尼西亚巨震的发震构造背景, 震后印、 缅板块的正应力减小, 剪应力相对增大, 剪应力是对华东地震形势产生影响的主要动力源。 简单统计印缅板块地震后3年内华东地区发生中强震的对应组数为21组, 利用概率增益公式得出印、 缅板块地震和华东地区中强震的对应关系是有物理基础的对应, 而不是随机的对应。 通过β分布函数预测华东地区未来3年发生5级以上地震的概率为0.67, 风险经验概率为0.65。     

Polyphase accretionary tectonics in the Jurassic to Cretaceous accretionary belts of central Japan

Abstract Mesozoic accretionary complexes of the southern Chichibu and the northern Shimanto Belts, widely exposed in the Kanto Mountains, consist of 15 tectonostratigraphic units according to radiolarian biochronologic data. The units show a zonal arrangement of imbricate structure and the age of the terrigenous clastics of each unit indicates successive and systematic southwestward younging. Although rocks in these complexes range in age from Carboniferous to Cretaceous, the trench-fill deposits corresponding to the Hauterivian, the Aptian to Middle Albian and the Turonian are missing. A close relationship between the missing accretionary complexes and the development of strike-slip basins is recognizable. The tectonic nature of the continental margin might have resulted from a change from a convergent into a transform or oblique-slip condition, so that strike-slip basins were formed along the mobile zones on the ancient accretionary complexes. Most terrigenous materials were probably trapped by the strike-slip basins. Then, the accretion of the clastic rock sequence occurred, probably as a result of the small supply of terrigenous materials in the trench. However, in the case of right-angle subduction, terrigenous materials might have been transported to the trench through submarine canyons and deposited there. Thus, the accretionary complexes grew rapidly and thickened. Changes both in oceanic plate motion and in the fluctuation of terrigenous supply due to the sedimentary trap caused pulses of accretionary complex growth during Jurassic and Cretaceous times. In the Kanto Mountains, three tectonic phases are recognized, reflecting the changes of the consuming direction of the oceanic plates along the eastern margin of the Asian continent. These are the Early Jurassic to early Early Cretaceous right-angle subduction of the Izanagi Plate, the Early to early Late Cretaceous strike-slip movement of the Izanagi and Kula Plates, and the late Late Cretaceous right-angle subduction of the Kula Plate.     

板块绝对运动及地幔热对流

本文以板块绝对运动AM1-2模型为边界条件探讨了不同的瑞利数下地幔热对流模型.结果表明,瑞利数小于10000（529.41）时,地幔对流呈现以板块驱动图式,运动的极型场和环型场由板块运动激发,两种场占有差不多相同的功率.当瑞利数增加到接近或略超过最低临界值时（约1.5倍）,对流呈现出复杂状态:1.板块运动速率小于下伏地幔对流速率;2.区域性的双层对流环出现;3.对流谱成分发生变化;4.环型场仅在地幔很浅的区域中起作用,而在地幔深部对流图式中影响很小.     

Seismic gaps and plate tectonics: Seismic potential for major boundaries

The theory of plate tectonics provides a basic framework for evaluating the potential for future great earthquakes to occur along major plate boundaries. Along most of the transform and convergent plate boundaries considered in this paper, the majority of seismic slip occurs during large earthquakes, i.e., those of magnitude 7 or greater. The concepts that rupture zones, as delineated by aftershocks, tend to abut rather than overlap, and large events occur in regions with histories of both long- and short-term seismic quiescence are used in this paper to delineate major seismic gaps.In detail, however, the distribution of large shallow earthquakes along convergent plate margins is not always consistent with a simple model derived from plate tectonics. Certain plate boundaries, for example, appear in the long term to be nearly aseismic with respect to large earthquakes. The identification of specific tectonic regimes, as defined by dip of the inclined seismic zone, the presence or absence of aseismic ridges and seamounts on the downgoing lithospheric plate, the age contrast between the overthrust and underthrust plates, and the presence or absence of back-arc spreading, have led to a refinement in the application of plate tectonic theory to the evaluation of seismic potential.The term seismic gap is taken to refer to any region along an active plate boundary that has not experienced a large thrust or strike-slip earthquake for more than 30 years. A region of high seismic potential is a seismic gap that, for historic or tectonic reasons, is considered likely to produce a large shock during the next few decades. The seismic gap technique provides estimates of the location, size of future events and origin time to within a few tens of years at best.The accompanying map summarizes six categories of seismic potential for major plate boundaries in and around the margins of the Pacific Ocean and the Caribbean, South Sandwich and Sunda (Indonesia) regions for the next few decades. These categories range from what we consider high to low potential for being the site of large earthquakes during that period of time. Categories 1, 2 and 6 define a time-dependent potential based on the amount of time elapsed since the last large earthquake. The remaining categories, 3, 4, and 5, are used for areas that have ambiguous histories for large earthquakes; their seismic potential is inferred from various tectonic criteria. These six categories are meant to be interpreted as forecasts of the location and size of future large shocks and should not be considered to be predictions in which a precise estimate of the time of occurrence is specified.Several of the segments of major plate boundaries that are assigned the highest potential, i.e., category 1, are located along continental margins, adjacent to centers of population. Some of them are hundreds of kilometers long. High priority should be given to instrumenting and studying several of these major seismic gaps since many are now poorly instrumented. The categories of potential assigned here provide a rationale for assigning prorities for instrumentation, for future studies aimed at predicting large earthquakes and for making estimates of tsunami potential.Lamont-Doherty Geological Observatory Contribution No. 2906.     

一条巨大的地震活动带（东北深震区－渤海－川滇－缅甸中深震区）的存在

本文研究了东北深震、缅甸中深震、渤海周围地震及川滇地震在活动进程中的关系。在地域分布上彼此相连。并呈以北东向斜贯中国东部浑然为有机整体巨大的地震带。同时还研究了东北深震与华北东部的渤海周围地震以及缅甸中深震与川滇地震活动的相关性和前兆性。指出了这些特点，对华北东部地震和川滇地震的预测是十分有意义的。文章在最后还讨论了太平洋、印度、欧亚三大板块的相互作用可能是巨大地震带形成的主要条件和产生变动的重要的动力因素。     

卫星重力场、地幔对流应力场与板块运动关系的探讨

本文采用GEM10C的前50阶系数,计算了全球自由空气重力异常和地幔对流产生的岩石层底部应力场.通过对全球重力异常、应力场的分析,着重讨论了板块运动与地幔对流间的关系.对各板块在地幔对流作用下受力的定性分析和定量计算表明,板块的运动主要由低阶应力场决定,板块底部多个地幔对流体（而不是一个以洋中脊为对流上涌中心的单个地幔对流）的共同作用,推动了现代板块的运动.     

斜俯冲板块边界变形分配的力学分析

本文研究斜俯冲板块边界由俯冲的逆掩断层和平行于火山弧的走滑断层所切割出的岩石层窄条的宏观力学状态．分析计算表明，当断层强度小而构造压应力大时，海沟处板块俯冲形成的逆掩断层地震滑动方向与斜收敛板块运动方向将不一致，震源机制反映的主压应力和断层错动方向变得近乎垂直于海沟；板块间的强耦合和大陆板块边缘软弱带的存在为窄条滑动提供了有利条件．给定俯冲倾角和震源机制滑动角的观测值，可以计算逆掩和走滑断层上的有效摩擦系数．计算结果表明，两种断层上的有效摩擦系数一般都不大于０．２，反映或存在着高孔隙水压，或存在断层泥之类弱物质，或两者兼而有之．     

板块俯冲中水分运移过程及其地球物理含义

流体/水分在地球演化过程中具有重要作用,它的存在可以提高地质体的扩散及蠕变,降低岩石/地幔的固液相限,对地质体的地球物理性质、地质灾害诱发、地质构造演化等都有着重要的作用.在板块俯冲区,流体/水分的影响贯穿了整个动力学过程,但板块深部脱水还存在着争议,且目前系统地研究水分在整个俯冲中的迁移过程及其地球物理意义的工作还较...     

Timing of collision of the Kohistan–Ladakh Arc with India and Asia: Debate

The Kohistan–Ladakh Arc in the Himalaya–Karakoram region represents a complete section of an oceanic arc where the rocks from mantle to upper crustal levels are exposed. Generally this arc was regarded as of Jurassic–Cretaceous age and was welded to Asia and India by Northern and Southern Sutures respectively. Formation of this arc, timings of its collisions with Asia and India, and position of collision boundaries have always been controversial. Most authors consider that the arc collided with Asia first during 102–75 Ma and then with India during 55–50 Ma, whereas others suggest that the arc collided with India first at or before 61 Ma, and then the India–arc block collided with Asia ca 50 Ma. Recently published models of the later group leave several geological difficulties such as an extremely rapid drifting rate of the Indian Plate (30 ± 5 cm/year) northwards between 61–50 Ma, absence of a large ophiolite sequence and accretionary wedge along the Northern Suture, obduction of ophiolites and blueschists along the Southern Suture, and the occurrence of a marine depositional environment older than 52 Ma in the Indian Plate rocks south of the Southern Suture. We present a review based on geochemical, stratigraphic, structural, and paleomagnetic data to show that collision of the arc with Asia happened first and with India later.