关于改进的Encke方法中参考轨道的选择和校正

对于改进的Ｅｎｃｋｅ方法，选择适当的参考轨道是一个关键．然而，对于人造地球卫星长弧轨道计算，目前所给出的几种参考轨道均需要逐段校正，这将给定轨问题带来附加的复杂性．本文将仔细探讨如何选择参考轨道和减少校正次数．     

利用历史有感地震目录（M≥3（1／2））研究华北地区地震活动性特征

对新编的华北地区历史有感地震目录（３（１／２）≤Ｍ＜４（１／２））的精度和可信度进行了讨论。认为该地震目录从１４８４年后的记载率较高，它的发震时间、震中位置和震级的精度基本可以满足研究历史地震活动性的需要。它与中国地震目录（Ｍ≥４（３／４））比较，补充了相当数量的３（１／２）≤Ｍ≤４（１／２）的地震。利用历史有感地震目录分析了华北北部部分６级以上的历史地震，结果表明，这些地震在强震发生前具有明显的空区、条带、地震活动性增强、平静等前兆特征，同时，也显示了某些强＊发生前的前震活动和主震之后起伏的强余震活动     

The characteristics of Asian dust events in Northeast Asia during the springtime from 1993 to 2004

The characteristics of Asian dust events that occurred in Northeast Asia during the springtime from 1993 to 2004 are investigated using 3-hourly SYNOP reports (World Meteorological Organization). Occurrences of blowing sand and dust storm are low in 1997 and 1999, but have increased rapidly since 2000. The maximum occurrence was recorded in 2002. Wind velocity of 6.5 m s^− 1 as a threshold wind velocity is not so exactly consistent with the occurrence of blowing sand. However, wind velocity of 14 m s^− 1 as a strong wind causing dust storm had similar tendency to those of dust storm and Dust Storm Index.Source regions of Asian dust are divided into three regions (A: dry arid, B: semi-arid, and C: cultivated), based upon the occurrence of blowing sand and dust storm. Eight meteorological stations are selected in three regions, which have frequent occurrences of blowing sand. Source regions of Asian dust that affect the Korean peninsula are gradually extending eastward. Positive anomalies of NDVI occurred in 1994, 1995, and 1998 when temperature was high and precipitation was heavy. However, the frequent occurrence of the dust phenomena is not always consistent with lots of vegetation, high temperature, and much precipitation in this study.     

Effect of spatial variation characteristics on contouring of design storm depth

The ordinary kriging method, a geostatistical interpolation technique, was applied for developing contour maps of design storm depth in northern Taiwan using intensity–duration–frequency (IDF) data. Results of variogram modelling on design storm depths indicate that the design storms can be categorized into two distinct storm types: (i) storms of short duration and high spatial variation and (ii) storms of long duration and less spatial variation. For storms of the first category, the influence range of rainfall depth decreases when the recurrence interval increases, owing to the increasing degree of their spatial independence. However, for storms of the second category, the influence range of rainfall depth does not change significantly and has an average of approximately 72 km. For very extreme events, such as events of short duration and long recurrence interval, we do not recommend usage of the established design storm contours, because most of the interstation distances exceed the influence ranges. Our study concludes that the influence range of the design storm depth is dependent on the design duration and recurrence interval and is a key factor in developing design storm contours. Copyright © 2003 John Wiley & Sons, Ltd.     

南海北缘北东东向构造活动性研究

从地形地貌特征、重磁地球物理场、深部构造与断裂构造以及地震活动、震源机制等多方面论述北东东向构造是南海北缘的主要活动构造。对于长期以来认为新华夏系北东向构造是该区主要活动构造的观点来说，这是一种新的学术思想。     

康古尔塔格缝合带的变形机制

北天山东段康古尔塔格带是晚古生代塔里木板块和准噶尔板块碰撞的结果。它是一条复杂的、强烈的高应变带．并具有独特的变形机制、应变序列以及构造变形。本文运用构造－地层研究方法对该碰撞带的构造特征加以分析和研究。     

Inversion of multimode surface wave data: evidence for sub-lithospheric anisotropy

Summary. Multiparameter inversions of multimode dispersion data are performed for two large regions: the Pacific Ocean and North America. Anisotropy is taken into account by considering transversely isotropic structures with a vertical axis of symmetry. Two fundamental questions are studied in detail: (1) how to make the inverted models consistent when using different sets of parameters, (2) what is the significance of transversely isotropic inversion for the actual Earth's structure? It is proved that full consistency of the inverted models can be achieved by properly taking into account some a priori informations on the model and it is shown that the use of transversely isotropic models with vertical axis of symmetry does not cause severe limitations when interpreting the data. The models we have obtained are discussed in the light of these investigations. Considering an olivine-rich upper mantle, we make a tentative interpretation of these models in terms of preferred orientation of the a -axis of the crystals in one fixed horizontal direction.     

Long-chain alkenones and U37′ variability along a south–north transect in the Western Pacific Ocean

In this paper, we present 50 surface water samples collected during the IMAGES III cruise (June–July 1997) along a transect from New Zealand to the China Sea (42°S–178°E, 21°N–120°E) covering a temperature range from 13.3 to 30.4 °C. A very worthwhile aspect of this study is a coupling of both biomarker (alkenone) and coccolithophorid counting. We show that the U₃₇^k′–temperature relationship is very similar to the Prahl et al. [Geochim. Cosmochim. Acta 52 (1988) 2203] culture calibration and to the global core top calibration of Müller et al. [Geochim. Cosmochim. Acta 62 (1998) 1757]. However, in the warmest surface waters of the Western Pacific ocean (>26.4 °C) where Gephyrocapsa oceanica is likely the most widespread species, the associated U₃₇^k′ has a constant value of 1.0. The consequence is that above this temperature threshold, U₃₇^k′ cannot be used as an accurate paleothermometer.     

Contribution of storms to groundwater recharge in the semi‐arid region of Karnataka,India

This paper describes the application of environmental isotopes and injected tracer techniques in estimating the contribution of storms as well as annual precipitation to groundwater recharge and its circulation, in the semi‐arid region of Bagepalli, Kolar district, Karnataka. Environmental isotopes ²H, ¹⁸O and ³H were used to study the effect of storms on the hydrological system, and an isotope balance was used to compute the contribution of a storm component to the groundwater. Some of the groundwater samples collected during the post‐storm periods were highly depleted in stable isotope content with higher deuterium excess relative to groundwater from the pre‐storm periods. Significant variation in deuterium excess in groundwater from the same area, collected in two different periods, indicates the different origin of air masses. The estimated recharge component of a storm event of 600 mm to the groundwater was found to be in the range of 117–165 mm. There was no significant variation in environmental tritium content of post‐storm and pre‐storm groundwater, indicating the fast circulation of groundwater in the system. After completion of the environmental isotope work, an injected radiotracer ³H technique was applied to estimate the direct recharge of total precipitation to the groundwater. The estimated recharge to the groundwater is 33 mm of the 550 mm annual precipitation during 1992. Copyright © 2003 John Wiley & Sons, Ltd.