Flat mantle reflectors in Eastern China: possible evidence of lithospheric thinning

Recent 24 s deep seismic reflection records revealed five flat reflectors in the lithospheric mantle in Eastern China. With increasing depth, they are named M1 to M5 and can be seen on both field single-shot and stacked records. Reflector M1 corresponds to the Moho discontinuity, whereas M5 may be the reflection from the bottom of the current lithosphere, which is about 78 km deep according to geothermal measurements. The other three reflectors seem peculiar and might result from interactions between the lithosphere and deeper mantle. Based on lithological and geochemical data, it is suggested that the lithosphere has been thinned from about 150 km to about 60 km in the Late Mesozoic, and then has been thickened to about 78 km during the Cenozoic. The thinning process produced a granulite layer in the old lower crust caused by magmatic underplating, whereas an eclogite layer formed beneath owing to the subduction of the Paleo-Tethys and Yangtze Craton during the Permian and Early Mesozoic. Reflector M2 at about 12 s two-way traveltime (TWT) might result from the Paleozoic Moho, which represents the boundary between the previous granulite and eclogite facies. Reflector M3 at about 14 s might correspond to the bottom of the eclogite layer, beneath which the old lithospheric mantle remained. The old and the newly developed mantle may have different compositions, resulting in reflector M4. The multi-layered mantle reflectors demonstrate a mantle structure that possibly correlates with the lithospheric thinning process that occurred in Eastern China during the Late Mesozoic. The discovery of multi-layered mantle reflectors in the studied areas indicates a high heterogeneity of the upper mantle. Reflection seismology with improved technology, together with velocity and resistivity imaging and rock-physics measurements, can provide more details of the heterogeneity and related dynamic processes that occurred in the lithospheric mantle.     

Confirmation of an Early Cretaceous age for the Qihulin Formation in eastern Heilongjiang Province, China: constraints from a new discovery of radiolarians

The coal-bearing, alternating marine and non-marine Longzhaogou Group in eastern Heilongjiang, northeastern China, has long been considered as Jurassic, or mainly Jurassic, in age. However, recent studies have demonstrated that the ammonites and dinoflagellate cysts are of Early Cretaceous age. This has now been confirmed by new radiolarian evidence. The radiolarian fauna recovered from the upper Qihulin Formation of the Longzhaogou Group consists of nine poorly preserved species referable to nine genera. Novixitus is a Cretaceous genus, and the specimens of Archaeodictyomitra sp. and Xitus sp. recovered resemble A. vulgaris Pessagno and X. spicularius (Aliev), respectively.     

使用Intel编译器优化中尺度模式MM5在奔腾4上的运行

本文介绍了一种在奔腾4处理器微机上Linux操作系统下的优化编译方法。作者通过查询、试验发现：使用Intel编译器优化中尺度模式MM5，能够使得MM5在奔腾4上的运行速度提高1．4～1．5倍。利用Intel编译器优化后的MM5模式，进行了三个月资料的计算，模式运行稳定。给出了一个使用Intel编译器和通常使用的PGI编译器分别编译的计算实例，对比表明：使用Intel编译器明显提高了运算速度，两种编译方法预报的降水场和形势场没有太大差异。     

华北汛期降水异常与100hPa高度场异常的关系

利用华北17站1951～2000年的逐月降水资料,与前期的100 hPa高度场(1958～1997年)求相关,找到了100 hPa高度场影响华北地区汛期降水的关键影响区为25°～35°N,85°～105°E,对应的关键影响时段为前一年3～5月.然后用SVD方法证实了前一年春季正是与华北汛期降水相关最显著的时段;而所选关键区正是处于一种范围更大的100 hPa高度场空间分布型的关键部位,而华北地区是关键区影响中国东部降水的最显著的区域之一.     

江西省夏季干旱特征分析

根据1951～2000年江西省降雨量、降雨日数、降雨变率等资料,统计和分析江西省夏季干旱期间降雨量、降雨日数、降雨变率等变化与地理分布客观特征.文章还对江西干旱标准、干旱指数与伏、秋干旱时空分布客观特征等进行分析.分析结果为江西人工增雨抗旱作业提供依据.     

长治市防雹作业新体系

本文根据长治市多年冰雹发生情况，经过分析统计，找出了冰雹多发源地、雹云发晨方向、路径和影响范围，提出了合理布局，联防作业，建立现代化作业指挥系统的防雹新思路。     

中国气象应用网格

“中国气象应用网格”是国家“863”项目“高性能计算机及其核心软件重大专项”的应用课题之一，发展基于网格技术的数值天气预报软件及其支持软件，观测资料和数值预报气象数据的海量处理技术，实现网格应用对海量气象数据集的无程访问。建成后的中国气象应用网格将是一个创新性的     

内蒙古色尔腾山山前断裂带乌加河段古地震活动

通过对色尔腾山山前断裂带乌加河段断层地貌研究，并结合前人对断裂带断裂活动性的工作，分析得到乌加河活动断裂段晚更新世晚期(距今1.445～2.234万年)以来平均垂直位移速率是0.48～0.75 mm/a，全新世早中期以来(距今5 570～8 830年)平均垂直位移速率是0.56～ 0.88 mm/a．利用5个探槽中揭露的古地震现象，结合前人对该断裂带古地震的研究结果，分析确定出2.7万年以来，色尔腾山山前断裂乌加河段共揭露出5次古地震事件，重复间隔约为4 300～4 400年．距今8 000～9 000年之间可能为一个古地震丛，而距今1～2万年之间可能遗漏了两次古地震事件．对比断层陡坎的高度与探槽中揭示出古地震事件的位移和，以及由断层平均位移速率和一次事件的位移得到古地震的重复间隔，得到阿拉盖兔探槽中缺失了3次古地震事件，整个活动断裂段上可能缺失了两次古地震事件．      

2001年11月14日昆仑山口西8.1级地震前地震活动性异常及其思考s

2001年11月14日在昆仑山口西发生了8.1级地震，震中位置为90.9E、36.2N．分析表明，8.1级地震前一些主要地震活动性异常都出现了，例如空区、条带、增强、平静和震群等，且与7级大震比较，这些前兆图象的演变具有类似的过程，所不同的是8.1级地震的前兆地震活动图象涉及的区域范围更大、地震震级更高，这为特大地震的前兆识别和预报提供了依据．最后回顾了对这次大震的粗略预测，并讨论了有关大震预测的某些问题．      

前驱地震波的试验研究及波谱分析

研究了含预置裂纹的有机玻璃试样在加载实验过程中，大破裂之前出现的长周期、小振幅低频事件，并与大地震前可能出现的同类现象（即前驱地震波）进行了对比研究，根据波形记录和频谱分析得出：前驱地震波是地壳介质的长周期波动，是一种客观存在的前兆特征，具有短临前兆意义。