1999年山西大同Ms 5.6地震的震源断层

大同震区先后在 1989、1991和 1999年发生MS >5地震 ,利用大同遥测地震台网的记录资料进行比较精确的地震序列震源定位 ,结合宏观烈度分布和震源机制解资料 ,详细地分析对比了 3次子序列的异同。结果显示 ,1999年MS5 .6地震的震源断层是走向NWW、长 16km、宽12km、埋深 5km以下、倾角近直立的左旋走滑断层。而前 2个子序列是NNE为主的右旋走滑断层活动所致 ,表明地震破裂方向发生了变化。这种 2个以上方向先后出现、并且强弱有别的地震破裂是普遍存在的 ,表明震源环境的复杂程度与地震序列的类型有关。虽然震区存在NE向的大王村断裂和NW向的团堡断裂 ,但目前没有证据说明震源断层和 2条构造断层连通。 3次子序列的震源断层都是走滑断层 ,也和 2条构造正断层有别。 1999年的子序列可能属于新破裂。     

昆仑山口西8.1级地震在四川地区的前兆异常效应

对昆仑口西8.1级地震发生前后四川地区地震前兆监测台网的测值曲线进行了系统的清理，发现存在有明显的孕震效应和震时效应，异常效应的幅度很大，容易鉴别，这对人类认识特大地震的影响场很有意义。     

2-D crustal structure of Changbaishan-Tianchi volcanic region determined by seismic traveltime inversion

IntroductionTrial-and-error forward modeling of wide-angle seismic reflection/refraction traveltimes for 2-D velocity structure is extremely time-consuming, even for experienced data interpreters. For wide-angle seismic reflection/refraction experiments that consist of numerous shots along a single line, it is quite difficult through repeated trial-and-error forward modeling to construct a 2-D model that fits the data within acceptable limits (Cerveny, et al, 1977; ZHANG, et al, 200 . In ad…     

Study and review on crust-mantle velocity structure in Bohai Bay and its vicinity

Introduction Bohai Bay, along with its adjacent areas, is one of the seismically active areas in North China. Understanding its crust/upper-mantle structural characteristics and lateral heterogeneity of the medium in this area is of great significance to the study of seismogenic environment, thus improvimg the level of earthquake prediction. For years, scientists have studied the area by gravity and magnetic methods (FENG, et al, 1989), geothermal field (WU, et al, 1988; TIAN, ZHANG, 19…     

介休井水位异常的调查与分析

从井孔周围地下水开采量变化、大气降雨补给量变化、农田灌溉用水量变化、矿井塌方、涌水、排水和地震活动等影响因素入手 ,对 1999年至 2 0 0 0年间介休井水位的 2次突降原因进行了调查。通过初步分析 ,表明介休井水位阶降型异常具有一定的震兆性质 ,其水位的缓慢上升与突然阶降意味着介休地区断裂活动在加速。其地震预测的意义是未来一段时间山西地震带内有发生MS≥ 5 0级地震可能     

Remote sensing analysis of desert vegetation and its landscape changes: The case in middle reaches of Tarim River Basin,Xinjiang, China

Based on remote sensing information sources including B/W aerial photos of 1983, pseudo-color aerial photos of 1992 and JERS-1/OPS VNIR image of 1996, vegetation types of Yingbazha, in the middle reaches of the Tarim River Basin in Xinjiang, China are mapped using ARC/INFO and related software. The changes in vegetation areas and distribution conditions are analyzed. As a result of natural and human influences, vegetation changes have temporal and spatial characteristics. According to the principles of landscape ecology and geographical information science, the landscape changes are indicated. Moreover, the remote sensing and GIS techniques are integrated to study vegetation and its landscape.     

Damage and recovery of the Gurbantunggut Desert vegetation following engineering activities

The fragile ecological environment of the Gurbantunggut Desert is damaged/disturbed by human activities relating to the development of oil-gas resources and the constructions of desert road and great engineering in the Jungger Basin. It was mainly represented: soil compaction, vegetation cleaning, burial of vegetation, oil polluting, and soil disturbance. With investigation and experiment, we found that when the way and intensity of engineering activities disturbing the eco-environment does not make its ecological stability disintegrated, the desert vegetation has a capacity of natural recovery. To speed and strengthen the process of vegetation recovery efficient assistant measurements, including stabilizing mobile sands promptly and sowing seeds of shrub and herb plants in good time will be needed.     

2001年四川省雅江-康定6.0级地震烈度考察及发震构造背景雏议

2001年2月23日四川省发生的6.0级地震，其宏观震中位于雅江县与康定县之间的高山峡谷地带．极震区烈度可达Ⅷ 度，Ⅷ 度区、Ⅶ 度区和Ⅵ 度区面积分别为180km2，1472 km2和3998 km2，等震线分布总体形态呈椭圆形，长轴近南北向．震区建筑物普遍受损，极震区山地灾害较为严重．初步分析认为，此次地震的发生与理塘断裂和玉农希断裂的长期活动有关，主干断裂活动造成的地壳应力调整和集中，最终在块体内部的次级断裂上释放而产生地震．      

用应变积累释放模型研究中国大陆地块分区地震活动

依据活动地块假说及活动边界的划分，对中国大陆地震活动进行分区．在此基础上，应用应变积累释放模型，通过地震应变积累释放的计算，研究了中国大陆各活动地块分区的地震活动性，初步探讨了各地块的地震活动阶段划分．此外，还对应变积累释放模型的应用前提条件进行了必要的讨论，并对模型结果中可能出现的问题给予一定分析．      

Efficient methods for solving water flow in variably saturated soils under prescribed flux infiltration

The non-linear solvers in numerical solutions of water flow in variably saturated soils are prone to convergence difficulties. Many aspects can give rise to such difficulties and in this paper we address the gravity term and the prescribed-flux boundary in the Picard iteration. The problem of the gravity term in the Picard iteration is iteration-to-iteration oscillation as the gravity term is treated, by analogy with the time-step advance technique, ‘explicitly’ in the iteration. The proposed method for the gravity term is an improvement of the ‘implicit’ approach of Zhang and Ewen [Water Resour. Res. 36 (2000) 2777] by extending it to heterogeneous soil and approximating the inter-nodal hydraulic conductivity in the diffusive term and the gravity term with the same scheme. The prescribed-flux boundary in traditional methods also gives rise to iteration-to-iteration oscillation because there is no feedback to the flux in the solution at the new iteration. To reduce such oscillation, a new method is proposed to provide such a feedback to the flux. Comparison with traditional Picard and Newton iteration methods for a wide range of problems show that a combination of these two proposed methods greatly improves the stability and consequently the computational efficiency, making the use of small time step and/or under-relaxation solely for convergence unnecessary.