关于我国开展地球系统研究战略概念模型的讨论

自20世纪末以来,地球科学开始进入一个新的发展时期,地球系统科学理念逐渐成为引领新世纪地球科学的发展方向。世界各国在制定其地球科学战略时,均基于各自掌握的科学资源和实际需求,形成了各自的特色。我国地球科学发展的优势在于区域自然条件,以及社会经济快速发展产生的需求和机遇。基于我国的实际情况的分析,提出了一个地球系统科学研究的概念模型。在这一框架内,我国可以在两方面选择研究范例,并为地球系统科学的发展做出贡献：一是在地球系统物质、能量循环中关注我国具自然条件优势的关键环节;二是强化区域集成研究。同时,还需要加强地球系统观测和模拟的平台建设。     

Statistical interrelation of 22-yr-long variations in the data on parameters of the Earth’s rotation and magnetic fields of the Earth and the Sun

By means of spectral analysis, oscillations have been detected in many-year time series of deviations in the duration of days from the standard that cannot be explained within the framework of existing gravitational theory. The solution of the problem of the origin and structure of these oscillations is associated with the essence of the phenomena taking place inside the Earth and the mechanisms of energy transfer by external fields and the Sun. The effect of the Sun on the Earth’s rotation also leads to the formation of a unified cyclic background, resulting in correlated oscillations in all shells of the Earth, as well as in its atmosphere and its nucleus. Ground magnetic fields of the Earth and the Sun play the leading role in the abovementioned unified cyclic process. The results of spectral autoregressive and wavelet analyses of experimental data concerning deviations in the duration of days from the standard in the years 1832–2006, ground geomagnetic field intensities in 1832–2006, and the mean magnetic field of the Sun during the period from 1975 to 2005 have been discussed in this paper to reveal and compare correlating oscillations. To analyze a short-period (31-yr-long) series of daily data on the mean magnetic field of the Sun, the results of wavelet transformations (the Morlet wavelet) of the detected amplitude of a burst envelope with a carrier frequency of 13 cycles/yr have been obtained.     

What was the Volatile Composition of the Planetesimals that Formed the Earth?

Is there an asteroid type or meteorite class that best exemplifies the materials that went into the Earth? Carbonaceous chondrites were once the objects of choice, and in the minds of many this choice is still valid. However, the origin of primitive chondritic meteorites is unclear. At the extremes they could either be fragments of very small parent bodies that never became hot enough to undergo geochemical modification other than mild lithification, or remnants of the uppermost layers of a body that had undergone a significant degree of internal differentiation, while the top layers remained cool due to radiative heat loss or loss of volatiles to space. This latter case is problematic if one considers these objects as precursors to the Earth since the timescale for the evolution of such a small body could be longer than the timescale for the accretion of the Earth. Large-scale circulation of materials in the primitive solar nebula could greatly increase the diversity of materials near 1 AU while also making the entire inner solar system both more homogeneous and much wetter than previously expected. The total mass of the nebula is an important, but poorly constrained factor controlling the growth of planetesimals. There is also a selection effect that dominates our sampling of the planetesimals that may have existed 4.5 billion years ago; namely, small fragile bodies are more likely to be lost from the system or ground down by collisions between small bodies, yet these are precisely those that may have dominated the population from which the Earth accreted. The composition of these aggregates could have played a very important role in the early chemical evolution of the Earth. In particular, the Earth may have been much wetter and richer in hydrocarbons and other reducing materials than previously suspected.     

Earth’s precession–nutation motion: the error analysis of the theories IAU 2000 and IAU 2006 applying the VLBI data of the years 1984–2006

The long-term systematic errors of the analytical theories IAU 2000 and IAU 2006 of the Earth’s precession–nutational motion are studied making use of the VLBI data of 1984–2007. Several independent methods give indubitable evidence of the significant quadratic error in the IAU 2000 residuals of the precessional angle while the adopted value of the secular decrease /cy of the Earth’s ellipticity e (derived from Satellite Laser Ranging data) should manifest itself in the residuals of as the negative quadratic trend . The problem with the precession of the IAU 2006 theory adopted as a new international standard and based on the precession model P03 (Capitaine et al., Astron Astrophys 432:355–367, 2005) appears to be even more serious because the above mentioned quadratic term has already been incorporated into the P03 precession. Our analysis of the VLBI data demonstrates that the quadratic trend of the IAU 2006 residuals does amount to the expected value (30.0 ± 3) mas/cy². It means, first, that the theoretical precession rate of IAU 2006 should be augmented by the large secular correction and, second, that the available VLBI data have potentiality of estimating the rate . And indeed, processing these data by the numerical theory ERA of the Earth’s rotation (Krasinsky, Celest Mech Dyn Astron 96:169–217, 2006, Krasinsky and Vasilyev, Celest Mech Dyn Astron 96:219–237, 2006) yields the estimate /cy statistically in accordance with the satellite-based . On the other hand, applying IAU 2000/2006 models, the positive value /cy is found which is incompatible with the SLR estimate and, evidently, has no physical meaning. The large and steadily increasing error of the precession motion of the IAU 2006 theory makes the task of replacing IAU 2006 by a more accurate model be most pressing.     

Comparison of TOPEX/POSEIDON Altimeter Derived Wind Speed and Wave Parameters with Ocean Buoy Data in the North Indian Ocean

Results of comparison exercises carried out between the state-of-the-art TOPEX/POSEIDON altimeter-derived ocean surface wind speed and ocean wave parameters (significant wave height and wave period) and those measured by a set of ocean data buoys in the North Indian Ocean are presented in this article. Altimeter-derived significant wave height values exhibited rms deviation as small as - 0.3 m, and surface wind speed of - 1.6 m/s. These results are found consistent with those found for the Pacific Ocean. For estimation of ocean wave period, the spectral moments-based semiempirical approach, earlier applied on GEOSAT data, was extended to TOPEX/POSEIDON. For this purpose, distributions of first four years of TOPEX/POSEIDON altimeter data and climatology over the North Indian Ocean were analyzed and a new set of coefficients generated for estimation of wave period. It is shown that wave periods thus estimated from TOPEX/POSEIDON data (for the subsequent two years), when compared with independent data set of ocean data buoys deployed in the North Indian Ocean, exhibit improved accuracy (rms ~ - 1.4 nos) over those determined earlier with GEOSAT data.     

Precursory groundwater level changes in the period of activation of the weak intraplate seismic activity on the NE margin of the Bohemian Massif (central Europe) in 2005

tWe analyse continuous measurements of groundwater level in two deep wells VS-3 and V-28 at the experimental hydro-meteorological station situated on the NE margin of the Bohemian Massif, central Europe, characterized by the weak intraplate seismic activity. The aim of our study is to examine the relationships between changes in the groundwater level and earthquake occurrence. Based on the tidal and barometric response of the water level, we estimated selected elastic parameters of the observed aquifers: the shear modulus G, the Skempton ratio B, the drained matrix compressibility β and the undrained compressibility β_u. Using these parameters and assuming the homogeneous poroelastic material, we derived the sensitivity of the wells to the crustal volume strain. During the observation period from November 1998 to December 2005 we detected in the VS-3 well two pre-seismic steps, related to August 10, 2005 (M = 2.4) and October 25, 2005 (M = 3.3) earthquakes. Amplitudes of the recorded precursory changes (+6 cm and +15 cm) are several times higher than the values predicted from the theoretical precursory crustal strain and the strain sensitivity of the well. Therefore, we presume that the observed pre-seismic water level steps can be attributed to heterogeneity of poroelastic material. We consequently propose the hypothesis of the origin of precursory events based on the presumption of a sensitive site, at which the well is situated.     

用强震动观测资料估算2007年宁洱M_S6.4地震震源参数

通过对2007年6月3日宁洱M_S 6.4、M_S 5.1两次地震的强震动台站观测记录的谱分析,估算了两次地震的辐射能量、地震矩、矩震级等震源参数.结果表明,虽然对拐角频率、应力降等参数各台站的估算结果离散性较大,效果不甚理想,但利用近场强震动观测记录,可以对地震辐射能量、地震矩、矩震级3个参数作出较好的估计.     

特克斯5.9级地震前后乌鲁木齐形变观测资料和断层出水异常分析

分析了2007年7月20日新疆特克斯5.9级地震前后乌鲁木齐形变站跨断层短水准及F2断层出水异常.该次地震前后乌鲁木齐形变站的形变资料出现了明显的短期形变异常及震后效应,也反映了现今雅玛里克山断裂带的最新构造运动.表明该台的观测手段对北天山中西部地区5.5～6.0级以上地震有较强的监控能力,并对乌鲁木齐周边及北天山中西部地区5～6级以上地震具有较好的临震前兆异常反映,这可能为震情趋势判断提供一定的依据.     

中国大陆井水温度潮汐动态的统计与调和分析

用收集到的全国356个井水温度测点的数据, 分析了水温对地球固体潮汐的响应, 统计出 35个存在水温潮汐现象的测点。 利用Baytap-G调和分析方法, 计算了水温潮汐分波的振幅、 振幅比和相位差。 结果表明: 水温潮汐现象是一类较普遍的地球物理现象, 其机制与水位潮汐相关, 可用水动力学模式解释; 水温潮汐变化特征还受太阳辐射热、 含水层和地温的影响, 自流井水温记录潮汐现象的能力高于非自流井、 东部地区水温测点记录潮汐现象的能力高于西部, 与太阳辐射热的影响有关, 在含水层附近的水温测点, 其潮汐动态比其他井段显著, 在受地温影响较大的井段, 水温的潮汐变化幅度与水温梯度成正比; 水温的应力-应变灵敏度量级为0.01～10℃/10^-6m·s^-2。     

基于GRACE Follow-On卫星重力梯度法精确反演地球重力场

由于GRACE Follow-On双星系统等效于基线长为星间距离的一维水平重力梯度仪,因此本文基于GRACE Follow-On卫星重力梯度法开展了精确和快速反演下一代地球重力场的可行性论证研究. 研究结果表明：第一,基于GRACE Follow-On卫星重力梯度法（GFO-SGGM）,利用卫星轨道参数（轨道高度250 km、星间距离50 km、轨道倾角89°、轨道离心率0.001）、关键载荷测量精度（星间距离10^-6 m、星间速度10^-7 m·s^-1、星间加速度10^-10 m·s^-2、轨道位置10^-3 m、轨道速度10^-6 m·s^-1、非保守力10^-11 m·s^-2）、观测时间30天和采样间隔10 s反演了120阶地球重力场,在120阶处累计大地水准面精度为9.331×10^-4 m. 第二,在120阶内,利用将来GRACE Follow-On双星反演地球重力场精度较现有GRACE双星平均提高61倍,因此GRACE Follow-On卫星重力梯度法是进一步提高地球重力场反演精度的优选方法. 第三,下一代GRACE Follow-On计划较当前GRACE计划的优点如下：轨道高度更低（200~300 km）、载荷精度更高（10^-7 ~10^-9 m·s^-1）和星间距离更短（50~100 km）.