Velocity structure of uppermost mantle beneath North China from Pn tomography and its implications   总被引：1，自引：0，他引：1  

汪素云  许忠淮  裴顺平 《中国科学D辑(英文版)》2003,46(Z2)

20301 Pn arrival time data are collected from the seismological bulletins of both national and regional seismic networks. Pn travel time residuals are tomographically inverted for the Pn velocity structure of uppermost mantle beneath North China. The result indicates that the average Pn velocity in North China is 7.92 km/s, and the velocity varies laterally from ?0.21 to +0.29 km/s around the average. The approximately NNE trending high and low velocity regions arrange alternatively west-eastward. From west to east we can see high velocity in the middle Ordos region, the Shanxi graben low, the Jizhong depression high, the west Shandong uplift and Bohai Sea low, and the high velocity region to the east of the Tanlu fault. In the southern boundary zone of the North China block, except for the high velocity in the Qingling Mountains region, the velocity is generally lower than the average. Obvious velocity anisotropy is seen in the Datong Cenozoic volcanic region, with the fast velocity direction in NNE-SSW. Notable velocity anisotropy is also seen around the Bay of Bohai Sea, and the fast velocity directions seem to show a rotation pattern, possibly indicating a flow-like deformation in the uppermost mantle there. The Pn velocity variations show a reversed correlation with the Earth's heat flow. The low Pn velocity regions generally show high heat flow, e.g., the Shanxi graben and Bohai Sea region. While the high Pn velocity regions usually manifest low heat flow, e.g., the region of Jizhong depression. This indicates that the Pn velocity variation in the study region is mainly aroused by the regional temperature difference in the uppermost mantle. Strong earthquakes in the crust tend to occur in the region with the abnormal low Pn velocity, or in the transition zone between high and low Pn velocity regions. The earthquakes in the low velocity region are shallower, while that in the transition zone are deeper.  相似文献   

上地幔顶部折射波走时层析成像研究综述   总被引：2，自引：0，他引：2  

裴顺平  许忠淮  汪素云 《地球物理学进展》2003,18(1):59-64

简要介绍了上地幔顶部折射波走时层析成像研究的发展历程，详细介绍了上地幔项部折射波走时层析成像研究的各种方法并分析了其优缺点，介绍了国内外有关上地幔顶部折射波的研究工作和成果，阐述了上地幔顶部速度结构与构造活动的关系及其地球动力学意义。  相似文献   

考虑震源破裂方向的地震动衰减模型          下载免费PDF全文

刘汉兴  汪素云 《地震学报》1989,11(1):24-37

本文基于Haskell的3源辐射谱模型,加上介质非弹性吸收项,几何扩散项和自由面放大效应,推演出峰值加速度和均方根加速度表达式。据此,建议一种考虑震源破裂方向的地震动衰减模型。用Morgan Hill和Imperial Valley两地震的峰值加速度资料,单震级统计分析结果表明,文中建议的地震动衰减模型是合理的。与Joyner和Boore所用的衰减模型相比较,剩余标准差可减少0.1——0.2。本文所考虑的震源破裂的地震动衰减模型,可分别用于不同断层类型的地震,如单侧和双侧走滑型地震及倾滑型地震,分别建立地震动衰减关系,进行地震危险性分析。文章最后给出了美国西部考虑震源破裂方向的地震动峰值加速度和均方根加速度的衰减关系。   相似文献   

鲁南地区地震动参数的衰减关系   总被引：5，自引：0，他引：5  

汪素云  武宦英 《中国地震》1988,(3)

本文选用了华北平原地区十个地震的39条等震线数据,拟合出鲁南地区烈度衰减的经验公式: I=2.429+1.499M-1.3911n(R+11) 根据上式,并参照美国西部烈度和基岩加速度衰减关系,按胡聿贤等建议的方法,估算得鲁南地区基岩加速度衰减公式: Ina=6.623 + 0.529M-1.4681n(R+11) 式中a为加速度,单位厘米/秒~2,M为震级,R为距离,单位公里。  相似文献   

A NUMERICAL STUDY OF SHORT-RANGE CLIMATIC OSCILLATION WITH VARIOUS TIME SCALES FORCED BY EL NINO DURING THE NORTHERN SUMMER          下载免费PDF全文

Ni Yunqi  Lin Wuyin 《Acta Meteorologica Sinica》1990,4(3):305-324

The normal mode method is adopted to decompose the differences between simulations with SST(seasurface temperature)anomahes over centra-eastern Pacific and normal SST by use of a nine-layer global spec-tral model in order to investigate short-range climatic oscillation with various time scales forced by ElNino during the northern summer.Investigation shows that El Nino may have the following influence onatmosphere on various space-time scales.Extra-long wave components of Rossby mode forced by convectiveanomaly over equatorial western Pacific resulting from El Nino produce climatic oscillation on monthly(sea-sonal)time scale in middle-high latitudes of Southern and Northern Hemispheres;extra-long wave componentsof Kelvin mode forced by SST anomalies propagate along the equator,resulting in 30—60 day oscillation oftropical and subtropical atmosphere;and its long waves move eastward with westerly,resulting in quasi-biweekoscillation.  相似文献   

DIAGNOSTIC STUDY FOR INTRASEASONAL OSCILLATION OF THE MIDDLE-HIGH LATITUDES IN A LOW RESOLUTION GLOBAL SPECTRAL MODEL     

Zhang Qin  Ni Yunqi  Lin Wuyin  Wang Zhaomin  D. D. Houghton 《Acta Meteorologica Sinica》1991,5(4):411-425

In this paper, five-year simulated data from a low-resolution global spectral model with triangular trunca-lion at wavenumber 10 are analyzed in order to study dynamical features and propagation characteristics ofintraseasonal oxillations over the mid-latitudes and the tropical atmosphere. The simulations show that thereis the 30-50 day periodic oscillation in the low-resolution spectral model without non-seasonal external forcing,and spatial scale of the intraseasonal oscihations is of the globe .Further analysis finds that propagation charac-ters of intraseasonal oscillations over the mid-latitudes and the tropics are different. The 30-50 day oscillationover the tropics exhibits structure of the velocity potential wave with wavenumber 1 in the latitudinal and thecharacter of the traveling wave eastward at speed of 8 longitudes/day. However, the 30-50 day oscillationsin mid-latitude atmosphere exhibit phase and amplitude oscillation of the standing planetary waves and theyare related to transform of teleconnection patterns over the mid-latitudes. The energy is not only transferredbetween the tropics and the middle-high latitudes, but also between different regions over the tropics. Based on the analysis of 5-year band pass filtered data from a 5-layer global spectral model of Jow-ordetwith truncated wavenumber l0,investigation is done of the source of intraseasonal oscillations in the extratropicalmodel atmosphere and its mechanism. Results show that (1) the convective heat transferred eastward alongthe equator serves as the source of the intraseasonal oxillation both in the tropical and the extratropical atmos--phere; (2) the velocity-potential wave of a zonal structure of wavenumber 1 gives rise to oxillation in divergentand convergent wind fields of a dipole-form as seen from the equatorial Indian Ocean to the western Pacificduring its eastward propagation, thus indicating the oscillation in the dipole-form heat soure:e/sink pattertl; (3)the tropical heat-source oscillation is responsible for the variation in phase and intensity of the extratropicalstationary wave train, and the interaction between the oscillating low-frequency inertial gravity and stationaryRossby modes that are probably mechanisms for the oscillations ip the middle-high latitudes.  相似文献   

华北强震断层面解和震源深度特征   总被引：17，自引：1，他引：17       下载免费PDF全文

汪素云 Ni  J 《地球物理学报》1991,34(1):42-54

本文利用远震P波及SH波和区域地震P_(nl)波波形反演方法,测定了华北9次强震的断层面解、震源深度及地震矩.结合其他作者测定的7次地震的结果,分析了华北16次强震断层面解及华北地震震源深度特征.结果表明,华北多数强震为走滑型地震,也有个别正断层型及逆断层型地震;16次地震多数发生在地壳中部10-25km深度范围内.  相似文献   

中国大陆内部走滑型发震构造的构造应力场特征   总被引：10，自引：0，他引：10       下载免费PDF全文

环文林  汪素云 《地震学报》1994,16(4):455-462

本文是笔者等中国大陆内部走滑型发震构造研究的系列论文之一。本文的第一部分根据大地震调查结果和最新的震源机制研究结果的大量数据, 讨论了中国及邻区大陆内部的发震构造。结果表明, 我国及邻区大陆内部不论在数量上、强度上、分布面积上, 占绝对优势的是走滑型地震, 进而强调了走滑型发震构造研究在地震危险性分析中的重要意义。第二部分讨论了走滑型发震构造的构造应力场特征, 以及根据各种性质断层面解的应力特征编制的中国及邻区大陆内部走滑型发震断层、正断层、逆断层的分布概况。   相似文献   

THE EFFECTS OF SEA SURFACE TEMPERATURE OVER THE EQUATORIAL WESTERN PACIFIC AND THE INDIAN OCEAN ON THE ASIAN SUMMER MONSOON   总被引：1，自引：0，他引：1  

Ni Yunqi  Qian Yongfu  Lin Yuanbi 《Acta Meteorologica Sinica》1989,3(3):375-394

In this paper,the p-σ five layer primitive equation model segmented by mountains and physical parameterizations including short wave radiation; long wave radiation; large-scale and convective condensation;heat and moisture transport from surface to the first model level is used.The horizonial resolution is 5° lat.×5° long.with the integration region from 25°S to 55°N and from 5°W eastward to 175°W.The model was spun up with perpetual June boundary conditions and forcing starting with June zonal mean heights and geostrophic wind field.In order to investigate the effects of SST (sea surface tempefuture) over the equatorial Western Pacific and the Indian Ocean on the Asian summer monsoon,four sets of numerical experments with positive anomalies over the equatorial Western Pacific,and positive and negative anomalies over the Western Indian Ocean,and zonal mean SST (the control case) are performed.The experimental results show that the South Asian low in the lower troposphere and the anticyclone over the South Asia in the uppet troposphere intensified when positive SST anomalies over the equatorial Western Pacific is included.A statistical test method for simulations is proposed.Finally,the influence mechanism of the SST anomalies over the equatorial oceans is discussed.It is worth stressing that the effects of the SST over the equatorial oceans on the Asian summer monsoon can arise as a result of interaction of SST anomalies,atmospheric flow field and heat sources and sinks in the atmosphere.  相似文献   

黄海、东海及邻区的地震构造应力场   总被引：7，自引：1，他引：7  

汪素云  许忠淮  葛民 《中国地震》1987,(3)

本文利用P波初动方向数据,测定了东海、黄海及邻区18个中、小地震的断层面解,结合其他作者所作的周围地区有关的震源机制解以及本文作者以前所作的小震综合断层面解,采用平面应力问题的有限元数值模拟方法,推断了该地区的构造应力场方向。结果表明本区应力场方向是大陆应力轨迹线向板块边界的自然延伸。  相似文献