1998年1～3月的全球地震动态

１９９８年第一季度,全球地震活动仍为高水平。南极洲附近巴勒尼群岛地区发生８级地震。伊朗东南部克尔曼省发生强烈地震。全球海岭地震带发生５次地震。全球地震轮回已进入新阶段。     

Research on the correlation between North China earthquake and global regional strong earthquakes

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全球巨大地震活动性分析

通过分析全球巨大地震活动周期、活跃时段和活动空间分布特征,探讨未来全球发生巨大地震的活跃时段和主体区域.结果表明:① 全球地震活动存在着置信度远超过95%的50年左右显著活动周期,此外还存在80——100年左右显著性不强的活动周期;② 通过对全球地震MSge;8.3时间序列图和MSge;8.0应变能时间序列图分析,得到活跃期10——14年,平静期39——41年,2004年后又进入了巨大地震的强活跃期,可能会一直持续到2018年;③ 强活跃时段内发生的MSge;8.5巨大地震存在着一定的相关性,太平洋板块北边界（美国阿拉斯加附近区域——阿留申群岛——千岛群岛）是发生8.5级以上地震最关注的地区,其次是太平洋板块的南美洲边界(尤其是秘鲁及其周边区域),应对这两个地区进行重点关注和监测．本文从地震活动性角度研究巨大地震的强活跃期问题,并推测全球发生8.5级以上地震的活跃时段和主体地区,而对于其机理问题值得进一步深入研究．      

三维复杂速度模型中地震的快速精确定位

讨论了全局选择震源初始位置下的矩阵反演求取全局解的问题．与流行的全局优化搜寻直接定位方法相比,该反演算法是一种行之有效的定位方法,具有定位精度高、计算时间少以及对噪声数据不敏感等特点．其突出的优点是在不增加计算难度和计算时间的前提下,用矩阵反演的方法确保得到全局最小值解,可适应于地震早期预警,海啸早期预警,以及大震速报等实际工作．      

基于应变率场的全球地震活动特征模拟探索

本文提出利用全球应变率资料模拟全球地震活动特征的基本思想, 并作了初步探索。 利用GSRM的全球应变率场结果, 初步设计了模拟全球地震活动时空分布特征的细胞自动机模型。 该模型把地球考虑为一个自组织的整体系统, 制定了细胞自动机的演化规则, 获得了模拟的人工地震目录。 初步的模拟结果基本反映了全球地震活动的主要分布特征, 体现了全球构造活动强弱的主要格局, 初步达到了利用GPS等实测资料计算的应变率作为细胞自动机网格状态及其改变量来模拟复杂的全球地震活动特征的实验目的。     

Towards constraining the magnitude of global agricultural sediment and soil organic carbon fluxes

Reliable quantitative data on the extent and rates of soil erosion are needed to understand the global significance of soil‐erosion induced carbon exchange and to underpin the development of science‐based mitigation strategies, but large uncertainties remain. Existing estimates of agricultural soil and soil organic carbon (SOC) erosion are very divergent and span two orders of magnitude. The main objective of this study was to test the assumptions underlying existing assessments and to reduce the uncertainty associated with global estimates of agricultural soil and SOC erosion. We parameterized a simplified erosion model driven by coarse global databases using an empirical database that covers the conterminous USA. The good agreement between our model results and empirical estimates indicate that the approach presented here captures the essence of agricultural erosion at the scales of continents and that it may be used to predict the significance of erosion for the global carbon cycle and its impact on soil functions. We obtained a global soil erosion rate of 10.5 Mg ha^‐1 y^‐1 for cropland and 1.7 Mg ha^‐1 y^‐1 for pastures. This corresponds to SOC erosion rates of 193 kg C ha^‐1 y^‐1 for cropland and 40.4 kg C ha^‐1 y^‐1 for eroding pastures and results in a global flux of 20.5 (±10.3) Pg y^‐1 of soil and 403.5 (±201.8) Tg C y^‐1. Although it is difficult to accurately assess the uncertainty associated with our estimates of global agricultural erosion, mainly due to the lack of model testing in (sub‐)tropical regions, our estimates are significantly lower than former assessments based on the extrapolation of plot experiments or global application of erosion models. Our approach has the potential to quantify the rate and spatial signature of the erosion‐induced disturbance at continental and global scales: by linking our model with a global soil profile database, we estimated soil profile modifications induced by agriculture. This showed that erosion‐induced changes in topsoil SOC content are significant at a global scale (an average SOC loss of 22% in 50 years) and agricultural soils should therefore be considered as dynamic systems that can change rapidly. Copyright © 2011 John Wiley & Sons, Ltd.     

1998年7～9月的全球地震动态

１９９８年第三季度,全球地震活动仍为中等水平,新几内亚北部近海和厄瓜多尔近海各发生一次７级以上地震,亚速尔群岛发生一次６级以上的地震,全球中等以上地震活动无异常现象。     

地下流体长趋势异常变化与强震预测的初步研究

以华北、川滇、青藏东北缘、新疆及邻区等重点地区的地下流体观测点为基础,选择水位、水氡、水温、汞等长期观测资料,进行了历史强震震例的地下流体长趋势资料处理、干扰排除和异常提取的方法和技术的研究,初步建立了分区的强地震地下流体长期预测指标并探讨其异同。     

1994年7─9月的全球地震动态

１９９４年第三季度，全球地震活动仍维持中等水平，西南太平洋的瓦努阿图群岛发生７．４级地震。美国加州北部海域发生７．０级地震。日本海西北部发生大深震，可以同日本海沟地震配合，对华北地震趋势作出估计。继台湾东部沿海两次７级地震之后，中国台湾海峡发生一次强震。     

1995年10—12月的全球地震动态

１９９５年第四季度。全球地震活动仍保持显著的高水平，地域分布比较广泛，活动强度与第二、第三季度相近。这显示１９９５年高水平活动的年份。美洲在智利地震之后发生墨西哥地震。     

1994年10—12月的全球地震动态

１９９４年第四季度，全球地震在维持了一年多的中等水平以后，出现了高水平的活动。全球地震如１９９３年，继续以西北太平洋地震带为中心，千岛群岛和日本本州以东接连发生海沟浅源大地震。１９９３－１９９４两年，全球最大地震发生在西北太平洋地区。菲律宾海周边地区发生强烈地震多次，日本南部近海海槽区发生大地震的形势更加迫近。中国大陆东半部地震活动有增强的迹象，１９９５年，中国华北地震活动将有新发展。本季度美洲地     

全球变化与植被

本文讨论了全球变化与植被的相互依赖与制约关系，以黄土高原为例，研究了古气候与植被之间的关系以及青藏高原隆升对黄河流域生态环境的改造，分析了人类活动对被的破坏给黄土高原生态系统的影响，提出了植被差异与变迁是引起气候快速和区域变化的主要原因。     

1994年1—3月的全球地震动态

1994年第一季度，全球地震活动仍为中等水平，三个月内共发生三次7级以上浅源地震。秘鲁－玻利维亚边界发生大深震。美国加州又发生强烈地震。大洋岛弧地震带本季度地震活跃。伊朗发生三次6级地震。     

1994年全球地震活动综述

１９９４年全球地震活动属于高水平，有４次大深震和４次浅源大地震。全球全年共发生６级以上地震１３４次，超过１９９３年。全球地震活动中心仍在太平洋西北边缘地震带。１０月４日的千岛群岛地震是最大的浅源地震；６月９日的玻利维亚地震是最大的深源地震。１９９４年全球地震活动开始转折，揭开强烈活动期的序幕。各大地震带的Ａ（ｂ）值几乎按同一比例上升，显示全球地震整体性增强。全球地震Ａ（ｂ）值在６月和１０月有两次高     

近60年全球大气环流经向模态的气候变化

本文根据1948～2004年NCEP/NCAR 1000 hPa、500 hPa、100 hPa高度场逐月再分析资料,分析了近60年全球大气环流经向模态的气候变化. 结果表明：近60年来第一模态从低层到高层都表现出高纬与低纬地区之间明显的反向变化关系,且随时间有明显的增强趋势. 第一模态位相发生了相反的改变,低纬地区由负距平演变为正距平,高纬地区由正距平演变为负距平. 1000 hPa和500 hPa高度场上的南半球比北半球变化激烈,而100 hPa高度场上的北半球比南半球变化激烈. 第二模态在1000 hPa高度场上,主要表现为南极涛动（AAO）和北极涛动(AO),且两涛动在年际、年代际尺度上表现出明显的负相关关系;在100 hPa高度场上,主要表现为南北半球高纬度地区之间的反向变化;500 hPa高度场是1000 hPa和100 hPa的一个过渡层次,主要表现出明显的南极涛动(AAO). 第二模态可能是南北半球中高纬环流相互作用的桥梁.     

1994年4－6月的全球地震动态

１９９４年第二季度，全球地震活动仍维持中等水平。爪哇岛以南爪哇海沟内发生以７．２级地震为主的强震序列。南美洲接连发生深震，６月９日玻利维亚北部发生大深震，有感范围极大。大洋岛弧带地震频数占全球半数以上，本季度最大地震也发生在此。亚欧带继续维持中等水平的活动，亚欧带西段地震活动的发展需要继续监视和跟踪。     

Improved method to derive equivalent current systems from global MHD simulations

Derivation of equivalent current systems(ECS)from a global magnetospheric magnetohydrodynamics(MHD)model is very useful in studying magnetosphere-ionosphere coupling,ground induction effects,and space weather forecast.In this study we introduce an improved method to derive the ECS from a global MHD model,which takes account of the obliqueness of the magnetic field lines.By comparing the ECS derived from this improved method and the previous method,we find that the main characteristics of the ECS derived from the two methods are generally consistent with each other,but the eastward-westward component of the geomagnetic perturbation calculated from the ECS derived from the improved method is much stronger than that from the previous method.We then compare the geomagnetic perturbation as a function of the interplanetary magnetic field(IMF)clock angle calculated from the ECS derived from both methods with the observations.The comparison indicates that the improved method can improve the performance of the simulation.Furthermore,it is found that the incomplete counterbalance of the geomagnetic effect produced by the ionospheric poloidal current and field-aligned current(FAC)contributes to most of the eastward-westward component of geomagnetic perturbation.     

张北6.2级地震前的电磁前兆信号的特征

通过对张北6.2级地震前辽中台接收的电磁信号研究分析，总结出这次距辽中台600km、6级地震前的电磁前兆信号，具有弱－强－弱－平静后发震的总变化过程。异常信息具有异常时间长、信号强、异常范围大的特征。     

Research on global change scientific satellites

Global change now poses a severe threat to the survival and development of mankind.Large-scale,real-time,highly accurate Earth observation from space has become a key technology used to observe global change.China is one of the most influential countries affecting and being affected by global change,yet it has no scientific satellite for global change research so far.Developing global change scientific satellites not only would meet an important demand of China,but also would be a valuable contribution to the world.By analyzing the mechanisms of space-based observation of variables sensitive to global change,this paper explores the concept of global change scientific satellites,and proposes a series of global change scientific satellites to establish a scientific observation system for global environmental change monitoring from space.     

Fast and accurate earthquake location within complex medium using a hybrid globallocal inversion approach

A novel hybrid approach for earthquake location is proposed which uses a combined coarse global search and fine local inversion with a minimum search routine, plus an examination of the root mean squares (RMS) error distribution. The method exploits the advantages of network ray tracing and robust formulation of the Fréchet derivatives to simultaneously update all possible initial source parameters around most local minima (including the global minimum) in the solution space, and finally to determine the likely global solution. Several synthetic examples involving a 3-D complex velocity model and a challenging source-receiver layout are used to demonstrate the capability of the newly-developed method. This new global-local hybrid solution technique not only incorporates the significant benefits of our recently published hypocenter determination procedure for multiple earthquake parameters, but also offers the attractive features of global optimal searching in the RMS travel time error distribution. Unlike the traditional global search method, for example, the Monte Carlo approach, where millions of tests have to be done to find the final global solution, the new method only conducts a matrix inversion type local search but does it multiple times simultaneously throughout the model volume to seek a global solution. The search is aided by inspection of the RMS error distribution. Benchmark tests against two popular approaches, the direct grid search method and the oct-tree important sampling method, indicate that the hybrid global-local inversion yields comparable location accuracy and is not sensitive to modest level of noise data, but more importantly it offers two-order of magnitude speed-up in computational effort. Such an improvement, combined with high accuracy, make it a promising hypocenter determination scheme in earthquake early warning, tsunami early warning, rapid hazard assessment and emergency response after strong earthquake occurrence.