GPS网可靠性强度分析

本文对GPS基线向量网的可靠性进行了探讨,提出了作为相关观测值的单个基线向量的可靠性指标和粗差检验方法,并通过对实测网和模拟网的计算与分析,得出了一些有关GPS基线向量网可靠性设计的建议和结论。     

On moisture flux across the sea surface

Available data on the water-vapor flux across the air-sea interface are processed to determine its coefficient. The results are found to be clearly divided into two regions; as the wind velocity increases the neutral transfer coefficient decreases at low winds, and increases at intermediate winds. The characteristics of aerodynamically smooth flows are demonstrated at low winds; the neutral transfer coefficient at intermediate winds increases linearly with the wind velocity, at nearly the same rate as the wind-stress coefficient. For various atmospheric conditions, the transfer coefficient varies systematically with the product between the wind velocity and the difference in humidities at the sea surface and at 10-m elevation. Readily applicable formulae are proposed for both low and intermediate winds.     

多剩磁成分的主成分法分离及其应用

岩石的多剩磁成分的分离是古地磁研究的重要环节之一.Kirschvink（1980）提出的主成分分析法（PCA）能有效地进行多剩磁成分的方向分离.作者认为,最大角偏差（MAD）值的选择应视各磁成分的剩磁谱组合特征而定,剩磁相似度的提出,可以帮助确定MAD值选取的最佳值.在主成分法分离的剩磁方向的基础上,作者提出了一种多剩磁成分的强度分离方法,籍此可以进一步研究各分离磁组分的剩磁谱特征及其成因,并将以上方法应用于新疆柯坪地区晚古生代地层的剩磁分离.     

湖州台的近震监测能力

本文根据湖州地震台DD-1地震仪记录的1980—1990年期间Δ<500km的近震资料和仪器放大倍率,利用理论计算Δ—Mmin曲线,b值检验3种方法,对湖州台的近震监测能力进行了估算和评价,得出了该台对目标监测区域内的有效监测震级。最后对区域地震台站的近震监测能力进行了讨论。     

北京地区夏季背景气溶胶的特征

本文通过对观测资料的统计分析和比较研究,初步揭示了北京地区夏季背景气溶胶的一些特征,其中包括元素浓度及其变化、富集因子和气溶胶来源等。     

PNA流型的年际变化及温、热带太平洋海温的作用

本文分析了PNA型环流的年际变化和影响因子,发现它存在两种优势周期振荡:一种是3—5年的振荡,另一种是10年左右的振荡.研究表明,前者与赤道太平洋海温的主要振荡周期相对应(同相关系),后者与北太平洋海温的主要振荡周期一致(反相关系).揭示了PNA型环流的变化与北太平洋海温比与赤道太平洋海温具有更密切的联系.并且由于北太平洋海温影响的频带与赤道太平洋海温的不同,它的作用有时与赤道太平洋海温的同相,有时则反相,使得ENSO与太平洋-北美地区大气环流和气候异常的关系变得复杂化.指出当考虑北太平洋海温的共同作用后     

晋陕豫交界区地震活动性分析

分析了晋陕豫交界区临汾、渭南地区的地震活动性,认为自1800年以来,运城地区地震活动明显增强,且有向韩城扩散的趋势     

The experimental study of acoustic emission during creep of rocks

Under normal temperature, the creep experiments with complete samples of Gabbro and Marble rocks are made under uniaxial compression. It is found that at the instantaneous creeping stage, AE activities increase with loading; at the steady creeping stage, large AE signals may appear at lower background of AE action, andm—value which shows the relationship between AE amplitude and frequency keeps stable on the low value or decreases; at the accelerate creeping stage, AE activities increase andm—value decreases quickly or decreases again after recovery. These experimental results are related to the quality of the samples. In this paper, AE activities during three stages of creeping process are connected with the seismic patterns (for exampleb—value, foreshocks). Finally, it is pointed out the possibility that the foreshock—mainshock—aftershock earthquake sequence has been formed by the mechanism of creep fracture of crustal rocks. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 104–112, 1991. This subject is sponsored by the Chinese Joint Seismological Science Foundation.     

Moment tensor inversion of some aftershocks of the April 18, 1985 Luquan earthquake of Yunnan Province, China

Based on the three component accelerograms, recorded at near-field distance by a temporary seismic network consisting of digital cassette tape recording accelerographs, the focal mechanisms of three aftershocks of the April 18, 1985, Luquan, Yunnan Province, China, earthquake ofM _S=6.1, are calculated using seismic moment tensor inversion technique. The phases of direct P, S and converted SP waves in the displacement seismograms, produced by twice integrations of the observed accelerograms, are identified via forward calculation using Green’s functions for homogeneous semi-infinite elastic medium, and used in the inversion. The results of inversion show that a better fit of synthetic to the observed seismograms of direct as well as converted phases can be achieved if appropriate weighting functions are used in solving the over definite linear equations. While these aftershocks are of different magnitudes (M _L=4.8, 3.2 and 3.5, respectively) and hypocentral locations, their focal mechanisms are very similar and consistent with that of the main shock. This feature demonstrates the intrinsic correlation between the occurrence of aftershocks and the seismogenic fault of main shock. Our experimentations show that using the near field accelerogram obtained from the digital seismic network with appropriate azimuthal coverage on the focal sphere, with the aid of even simple medium model, not only the shear dislocation source, but also the isotropic part and CLVD (compensated linear vector dipole) can be retrieved by the technique of moment tensor inversion. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 412–419, 1991. This work is supported by the Chinese Joint Seismological Sciences Foundation and the Western Yunnan Earthquake Prediction Test Site (WYEPTS), State Seismological Bureau.