生活在不平静的行星上的计划设立美国航空航天局的固体地球研究议程

现在和未来20年固体地球科学所面临的最大挑战是什么?而对美国国家航空航天局(NASA)来说，在与其他机构合作时，什么又是解决这些挑战的最好途径呢?一份《在不平静的行星上生活》的新报告，为回答这些问题提供了一份蓝图。根据这份报告，未来5年，固体地球科学领域最优先的一次新的宇宙飞船飞行行动是发射一颗干涉测量合成孔径雷达(inSAR)卫星。在NASA的要求下，固体地球科学工作组(SESWG)为太空机构未来25年固体地球科学的最优先目标制定了一个战略。该战略提出6个挑战，它们都具有基础科学的重要性，对社会有着重要意义并且能够通过在太空进行一系列共同的科学观测而取得实质性的进展。成功应对这些挑战将有赖于在其他的NASA计划方面与许多美国联邦机构以及国际合作伙伴之间进行密切合作和协作。固体地球科学工作组提出的计划分为5个观测方面，每一方面都将面对众多的科学挑战：陆地表面的形变、高分辨率地形和地形的变化、地球磁场的变异性、地球重力场的变异性以及地球变化表面的成像光谱。该工作组的评议工作已进行了两年(2000～2002年)，包括与广泛的地球物理学团体之间进行卓有成效的对话。AGU2000年秋季和2001年春季会议的代表帮助达成了广泛的共识，并设立了网站，用于给出委员会的进展报告并邀请所有感兴趣的人士反馈意见。由华盛顿卡内基研究所的Solomon任主席的固体地球科学工作组由19位代表组成，分别来自大学、研究机构、美国航空航天局和美国地质调查局。总报告可以在http：／／solidearth．jpl．nasa．gov上找到。     

Methods for Calculation of Geogenetic Depth

Some current methods for the calculation of the geogenetic depth are based on the hydrostatic model, it is induced that the depth in certain underground place is equal to the pressure divided by the specific weight of rock, on the assumption that the rock is hydrostatic and overlain by no other force but gravity. However, most of rock is in a deformation environment and non-hydrostatic state, especially in an orogenic belt, so that the calculated depth may be exaggerated in comparison with the actual depth according to the hydrostatic formula. In the finite slight deformation and elastic model, the relative actual depth value from the 3-axis strain data was obtained with the measurement of strain including that of superimposed tectonic forces but excluding that of time factor for the strain. If some data on the strain speed are obtained, the depth would be more realistically calculated according to the rheologicai model because the geological body often experiences long-term creep strains.     

Effects of Tectonic Force on Hydrostatic Pressure in Crust

The research into the hydrostatic pressure in the crust has been previously conducted from the viewpoint that the hydrostatic pressure is equal to the gravity, based on the fact that the hydrostatic pressure is derived mainly from the gravity of its overlying rocks. In this paper, the stress state of any point in the crust is suggested to have been caused by both the gravity and the tectonic force. The author proposes that the hydrostatic pressure is a combination or superposition of two isotropic stresses in the tectonic force and gravity stress fields. The results obtained with a finite-element simulation indicate that the additional hydrostatic pressure borne by rocks decreases gradually from the compression zone (pc^s),the shear zone (psh^s) to the tensile zone (pt^s), and that the difference in the additional tectonic hydrostatic pressure between these deformed zones tends to increase, following the increase in the absolute value and/or the difference in external forces between different directions. This paper presents the foundation for the research into the tectonic physicochemistry.     

Geobarmal Gradient in Orogenic Belt and Metamorphism Caused by Ultrahigh Pressure

The components and structures of lithosphere,inhomogeneous,are changing incessantly in different periods.Therefore,the state of load,called the pressure,in lithosphere is also incessantly changing.When the lithosphere volume remains the same,namely on the premise of isovolumes,the geobarmal gradient is:(dp/dh)v=(p/(e)h)v (p/(e)T)v(dT/dh)v.If β=(dp/dh)v/(p/(e)h)v is supposed,then β=1 rg-1Cv (dT/dh)v.When the geothermal degree in (dT/dh)v is zero,then the pressure grade of lithosphere is equal to the lithostatic grade,which is the minimum value in the pressure grade of lithosphere.Suppose that the lithosphere is made only up of quartz,Cv≌Cp=0.782 5.718×10-4 T-1.883×104T-2 (J·g-1·K-1) is obtained,which is the minimum one in lithospheric rock,and then the geothermal grade value of 20 ℃/km is calculated according to the geophysical transection data of Qinling Mountain orogeny.The results show that the high-pressure and ultrahigh-pressure eclogites in Jiangsu Province and Huangzhen,Dabie may,on the condition of incompletely isovolumes,occur in the depths of 17-40 km with the increase in geothermal temperature,whose values of β do not correspond to the theoretic value of 3.08.     

Primary Deformation Analyses of High Pressure Metamorphic Rock in Western Dabie Mountain Area

In the western Dabie Mountain area, the eclogites have similar compositions and tectonic environment, which could be contrastively researched. Except for the reservation of the early structural deformation inside and outside of the eclogite lens, there is no obvious difference between the characteristics of the foliation and lineation in the eclogite lens from the one in surroumding region. So this paper concludes that the eclogites or blueschists (high pressure metamorphic rocks, i. e. HPM) are basically situated in the original position. The eclogites are mostly superposed by the ductile shear zone and show the feature of structural displacement, but so far we have not discovered any large-scale structural zone to uplift eclogite return. Based on the analyses of finite strain measure, petrofabric analysis and TEM image for some minerals such as quartz and garnet, we could efficiently know the deforming characteristics of the eclogite in the prophase and anaphase of the main deforming epoch, and finally determine the forming condition of eclogite according to the strain and the differential stress. This paper puts forward preliminary conclusion that some HPM rocks could be formed by the deep-layer embedding and local stress concentration in the process of regional metamorphism.     

2004年12月26日苏门答腊—安达曼特大地震

发生在2004年12月26日（Mw=9．1～9．3级）和2005年3月28日（Mw=8．6级）的地震是过去40年中最大的两次地震，它们在欧亚大陆板块的东南部和印度-澳大利亚板块之间裂开一条长达1600km的断层。其中第一次地震引发的海啸吞噬了28．3万多人的性命。苏门答腊岛班达亚奇附近的断层滑动了15m，但是在其北边，沿着尼科巴群岛和安达曼群岛，断层快速滑动的距离则小了很多。海啸和测地学的观测表明，在50min或更长的时间范围内北部的断层发生了更多的缓慢滑动。     

The anomalous variation of the lightning activity in southern China during the 1997/98 El Nio event

The El Ni?o Southern Oscillation (ENSO) is a cli- mate anomaly responsible for worldwide weather im- pacts ranging from droughts to floods. It is of scien- tific importance to clarify the influences of the 1997/98 El Ni?o event (for simplicity, named the ENSO) on the regional and global lightning activity. Goodman et al.[1] noticed that during the El Ni?o ma- ture phase from December 1997 to February 1998, the total lightning frequencies recorded by LIS, lightning days and lightning ho…     

Regional and synoptic-scale features associated with inactive periods of the summer monsoon over south china(1)

This paper presents an observational study of the physical processes responsible for the inactive period (break) of the summer monsoon over South China (SC). The break of the monsoon is defined by using the rainfall data over Hong Kong Meteorological parameters provided by the European Centre for Medium-Range Weather Forecasts (ECMWF) for the period 1985-1990 are examined. Daily values of each parameter for the six years are then composited each day for the period of 5 days before to 1 day after the break. It is found that several days before the break, changes opposite to those occurred during the onset and active periods begin to take place. This suggests that a feedback mechanism is present which tends to restore the atmosphere to a more stable state. This mechanism may be initiated by the formation of convective clouds during the onset and active periods. These clouds then reduce the solar radiation to the ground, leading to a gradual drop in the temperature. This drop, together with the cooling of the atmosphere due to the large amounts of rainfall, causes the pressure over the SC region to become higher, which in turn induces a westward extension of the subtropical ridge. The decrease in temperature over SC may also shift the location of the heat source to the west, which leads to a concomitant westward shift of the convergence of the southerlies and results in less moisture-laden air reaching the SC region. The atmosphere then becomes unfavourable for heavy convection and therefore a break starts.