美国地震学会通报(BSSA)2008年四川汶川地震专集介绍

四川汶川MW7．9地震发生在2008年5月12日北京时间14时28分（国际协调时问6时28分）。地震的突然来袭令人措手不及,因为这个位于青藏高原边缘的地区并没有被列为地震高危险区。地震造成了巨大破坏：400多万居民无家可归,伤亡人数超过8万,并有重大的经济损失。这次地震是中国近几个世纪以来最大的地震灾难之一,     

Comparative Study on Two Methods for Measuring Wave Velocity Change of Crustal Medium Based on Large Volume Airgun Excitation Data

This paper proposes the application of dynamic programming method to calculate the relative change of wave velocities and compares its similarities and differences with the cross-correlation delay estimation method based on interference. The results show that:①the trend of wave velocities obtained by cross-correlation method and dynamic programming method are consistent. Besides,it is considered that the calculated result using cross-correlation delay method is reliable.② Compared with the cross-correlation delay method,the calculated result of the dynamic programming method has a magnifying effect and is more sensitive to small disturbances.③ Under ideal conditions,the wave velocity change trend calculated by P-wave and S-wave phase should be consistent. In addition,the cross-correlation delay method is used to calculate the wave velocity change.Under appropriate conditions,the process of recovering from the suspected wave velocity before the M_L1. 1 earthquake near the airgun source can be observed.     

Thermoluminescence Dating of Colluvial Deposits and Its Application to Chronological Study of Paleoearthquakes

On the basis of studies of lithofacies features of colluvial deposits, applicability of thermoluminescence dating of the colluvial deposits at different lithofacies positions, and reliability of the dating result, the thermoluminescent ages of colluvial deposit from different types of faults were determined. From the above, the ages of paleoseismic events and their recurrence intervals on the related fault were deduced.     

Experimental Studies on Elasticities of Forsterite-Enstatite Composites:Towards an Understanding of the Rules of Mixture

Which rule of mixture is the best for predicting the overall elastic properties of polyphase rocks based on the elastic properties and volume fractions of their constituents? In order to address this question, we sintered forsterite-enstatite polycrystalline aggregates with a varied forsterite volume fraction (0, 0.2, 0.4, 0.5, 0.6, 0.8, and 1.0). Elastic properties (shear, bulk, and Young's moduli) of these synthesized composites were measured as a function of pressure up to 3.0 GPa in a liquid-medium piston-cylinder apparatus using a high-precision ultrasonic interferometric technique. The experimental data can be much better described by the shear-lag model than by the commonly used simple models such as Voigt, Ruess and Hill averages, Hashin-Shtrikman bounds, Ravichandran bounds, Halpin-Tsai equations, and Paul's calculations. We attributed this to the fact that the elastic interaction and stress transfer between phases are neglected in all the models except for the shear-lag model. In particular, t     

Modeling N2O Emissions from Agricultural Fields in Southeast China

DNDC, a rainfall-driven and process-oriented model of soil carbon and nitrogen biogeochemistry, is applied to simulate the nitrous oxide emissions from agricultural ecosystem in Southeast China. We simulated the soil N₂O emission during a whole rice-wheat rotation cycle (from Nov. 1, 1996 to Oct. 31, 1997) under three different conditions, which are A) no fertilizer, B) both chemical fertilizer and manure and, C) chemical fertilizer only. The processes of N₂O emission were discussed in detail by comparing the model outputs with the results from field measurement. The comparison shows that the model is good at simulating most of the N₂O emission pulses and trends. Although the simulated N₂O emission fluxes are generally less than the measured ones, the model outputs during the dryland period, especially during the wheat reviving and maturing stages in spring, are much better than those during the paddy field period. Some sensitive experiments were made by simulating the N₂O emissions in spring, when there is a smallest gap between the simulated fluxes and the measured ones. Meanwhile, the effects of some important regulating factors, such as the rainfall, N deposition by rainfall, temperature, tillage, nitrogen fertilizer and manure application on N₂O emission during this period were analyzed. From the analysis, we draw a conclusion that soil moisture and fertilization are the most important regulating factors while the N₂O emission is sensitive to some other factors, such as temperature, manure, tillage and the wet deposition of atmospheric nitrate.     

全球植被与大气之间碳通量的模式估计

用大气植被相互作用模式(AⅥM)模拟了全球陆地植被的净初级生产力(NPP)。AⅥM由相互耦合的两部分组成：物理过程，包括陆地表面水分和能量在土壤、植被与大气之间的传输；以及生理生态过程，如：光合、呼吸、干物质分配、凋落和物候等。全球的植被分为13类，土壤按质地分为6类。用EMDI提供的全球1637个包括不同植被类型的NPP观测点数据对模型进行了检验。NPP模拟的结果表明：全球陆地植被的平均NPP为405.13 g C m-2yr-1，不同植被类型的平均NPP变化范围在99.58 g C m-2yr-l(苔原)到996.2 g C m-2yr-l(热带雨林)之间。全球年总NPP为60.72 Gt C yr-l，其中最大的部分为热带雨林，15.84 Gt C yr-1，占全球的26.09％。最大的碳汇是在北半球的温带。模式模拟的NPP在全球的空间和季节分布是合理的。     

集合方法在月动力预报信息提取中的应用

本工作将集合方法应用于提取月动力预报有用信息。利用中国气象局国家气候中心Ｔ６３Ｌ１６全球谱模式的５００百帕高度场月集合预报产品（集合成员数为８个，初始场的选取采用滞后方法（ＬＡＦ），即相邻两天的００００，０６００，１２００和１８００ＧＭＴ的初始化资料），就１９９７年１月至５月共１５次预报，分析了集合预报成员间的离散度与预报评分（距平相关系数和均方根误差）的关系，研究了用集合各成员预报离散度作为各个成员逐日预报的权重对月预报效果的影响。结果表明集合预报成员的离散度与预报评分有显著的相关，是有效预报长度Ｎ的一个很好估计；用离散度作为权重平均的月预报高度距平相关系数明显高于算术平均和线性权重，此外个例分析表明月平均环流及其异常的预报得到明显的提高。     

与EAWM相关的海陆气相互作用及亚洲夏季风

基于观测资料分析，本文讨论了与东亚冬季风（EAWM）异常活动相联系的海－陆－气系统的特征，指出它往往是随后亚洲夏季风异常的一个信号。我们分析并确定了一类重要的海气耦合模态，即EAWM。它所包含的海－气双向相互作用，使该模态的SSTA分布得以发展和持续。特别是在西太平洋和南海等关键地区，SSTA异常将从冬季维持到夏季。在强冬季风年，青藏高原积雪冬季在其东部出现负距平区，春季则延伸到高原西北部。SSTA及高原积雪分布，共同构成调制亚洲季风环流的重要因子，它将有助于1）随后南海季风和季风降水的增强；2）梅雨期西太平洋副高偏北，长江流域少雨；3）夏季我国东北和日本多雨；4）阿拉伯海和印度东北多雨，而印度西南部及孟加拉湾少雨。总之，强EAWM及相联的海气相互作用，一定程度上，预示着亚洲夏季风的活动特征。     

RESPONSE OF TROPICAL ATMOSPHERIC CIRCULATION TO THE OCEAN-LAND SURFACE HEATING——AN ANALYTICAL SIMULATION

A linear steady model is constructed to investigate the response of the tropical atmosphere to diabaticheating.The basic equations are similar to those used by Gill(1980),but the long-wave approximationis removed and periodic boundary conditions are taken in longitude.According to the features of theunderlying surface temperature(including oceans and land),the heat sources(sinks)are given.Using thisanalytical model,we have simulated the climatological fields of wind and air pressure in the lower layersof the tropical and subtropical atmosphere in summer(June—August)and winter(December—February).The main features of observations are depicted in simulated fields.     

CHARACTERISTICS OF THE SURFACE AND ATMOSPHERIC HEATING FIELDS OVER QINGHAI-XIZANG PLATEAU FOR THE PERIOD FROM AUGUST 1982 TO JULY 1983

The surface and atmospheric heating fields over the Qinghai-Xizang Plateau are computed by using theobservational data of solar radiation during 1982—1983.The mian results are as follows:The central andnorthern parts of the Plateau act as heat sinks in winter from November to January.Both eastern and south-ern parts of the Plateau are of heat sources.In summer,the main part of the Plateau acts as a strong heatsource,and the center of the heating field is in the southeastern Plateau.However the main part of thePlateau acts as a heat sink for the atmospheric heating fields from October to March.The maximum intensityof the atmospheric heat sink over the central Plateau appears in December and January.From April toSeptember,the main part of the Plateau acts as a heat source for the atmospheric heating fields.