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大理岩的波速各向异性测量 总被引：4，自引：0，他引：4
利用 GC- 1 0 0型工程多波参数分析仪 ,对山东莱州大理岩进行了波速各向异性的实验室观测。实验采用两组岩样 ,一组为带有先天的优势定向排列裂缝的岩样 ,另一组为带有优势层理走向的完整岩石。在未加载的状态下 ,发现两组岩样都有明显的波速方位各向异性。对于带有先天的优势定向排列裂缝的岩样 ,甚至可以在无加载状态下观测到剪切波的分裂现象 相似文献
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YRY-4型钻孔应变仪观测的P波剪应变 总被引：2，自引：0，他引：2
传统地震仪观测的是一个点的位移随时间的变化, 而应变仪观测的是位移的空间导数随时间的变化。 在四川姑咱台用YRY-4型四分量钻孔应变仪进行的每秒100次采样观测实验, 记录到三次地方震。 在这样高的采样率下, YRY-4型四分量应变仪观测数据保持了令人满意的自洽和足够高的信度。 观测表明, P波的应变不仅有面应变成分, 而且有剪应变成分。 这为澄清P波的性质, 给出了直接的观测证据。 根据弹性波理论, P波无旋转, 可以有体应变和剪应变成分。 相似文献
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传统地震资料处理将多次波视为干扰波进行压制,而多次波是有效波在地层中来回传播的反馈,因此它携带了地层反射系数信息。本文从多次波成因出发,推导出反射系数公式(反射系数等于一阶多次波与一次反射波的反褶积)。理论模型实验证明了该方法的正确性。对实际海洋单道地震资料进行处理,求取的反射系数与有效波基本吻合,但由于资料信噪比、子波及反褶积算法等局限性,该技术有待进一步研究。 相似文献
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Wave measurement and modeling in Chesapeake Bay 总被引：4，自引：0，他引：4
Three recently measured wind and wave data sets in the northern part of Chesapeake Bay (CB) are presented. Two of the three data sets were collected in late 1995. The third one was collected in July of 1998. The analyzed wind and wave data show that waves were dominated by locally generated, fetch limited young wind seas. Significant wave heights were highly correlated to the local driving wind speeds and the response time of the waves to the winds was about 1 h. We also tested two very different numerical wave models, Simulation of WAves Nearshore (SWAN) and Great Lakes Environmental Research Laboratory (GLERL), to hind-cast the wave conditions against the data sets. Time series model–data comparisons made using SWAN and GLERL showed that both models behaved well in response to a suddenly changing wind. In general, both SWAN and GLERL over-predicted significant wave height; SWAN over-predicted more than GLERL did. SWAN had a larger scatter index and a smaller correlation coefficient for wave height than GLERL had. In addition, both models slightly under-predicted the peak period with a fairly large scatter and low correlation coefficient. SWAN predicted mean wave direction better than GLERL did. Directional wave spectral comparisons between SWAN predictions and the data support these statistical comparisons. The GLERL model was much more computationally efficient for wind wave forecasts in CB. SWAN and GLERL predicted different wave height field distributions for the same winds in deeper water areas of the Bay where data were not available, however. These differences are as yet unresolved. 相似文献
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利用横波分裂分析获取地下介质的各向异性参数,已成为研究壳幔介质变形特征最为有效的方法之一。本文首先介绍横波分裂理论方程的推导过程;然后阐述目前几种较为常用的拾取横波分裂参数的方法;最后总结近年来横波分裂分析方法的发展现状及其在地壳介质各向异性研究方面取得的成果。我们认为尽管横波分裂分析方法被广泛应用于地壳介质各向异性研究,但是它也存在一些固有的局限性,期望未来能发展一种更为可靠、有效的方法以及数据处理流程来准确拾取横波分裂参数。 相似文献
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Paul D. Komar 《地球表面变化过程与地形》1998,23(5):415-428
The Lone Tree landslide is located on the coast north of San Francisco, California, and is unusual in that it is positioned within the San Andreas fault zone. Its material ranges from mud through to boulders, which makes the slide particularly susceptible to mass movement. Movement of its western half increased following the Loma Prieta earthquake in 1989, closing an important highway for over a year, at which time a large cut-and-fill operation was undertaken to remove the upper portion of the slide so it would create no future disruption. Material cut from the upper slide was dumped below the highway, with the debris extending into the ocean. This created an artificial debris fill that is equivalent to a massive natural landslide, and a unique opportunity to monitor its erosion. Rainfall quickly eroded a series of rills into the face of the artificially created landslide, but the concentration of gravel and cobbles armoured these small channels, greatly reducing the rate of subsequent erosion. Waves cut away the toe, and the focus of this paper is on the development of a model to analyse the frequency of wave attack in terms of tide levels and wave conditions. A beach consisting of cobbles and boulders formed at the toe of the debris, offering partial protection and reducing the rate of continued erosion. In the short term, armouring of the rills and the development of a fronting beach have reduced the overall erosion of the debris and the transfer of sediment to the ocean. In the longer term, the formation of secondary slumps can be expected to renew the erosion. Eventually the morphology of the debris fill should approach the configuration of the natural landslide, an unmodified portion of which remains adjacent to the artificial fill. © 1998 John Wiley & Sons, Ltd. 相似文献
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利用目前工程上广泛应用的一维土层地震反应计算程序对成都平原某典型卵石场地剖面进行了计算,得到了不同输入地震强度下的加速度峰值随输入界面处剪切波速增大的变化规律。结果表明,无论是地表加速度峰值,还是地下5m处的加速度峰值,在相同的地震动输入强度下,均随着输入界面处剪切波速值的增大呈对数形式增大。且在小震输入下的增加速率最快,中震输入下的增加速率次之,大震输入下增加的速率最慢。当地震动输入界面处剪切波速值从500m/s增加至800m/s时,加速度峰值均增大20%以上,最大达到32%。统计得到的二者间的经验关系式,可作为本地区具有相似场地条件工程换算加速度峰值的经验公式,为工程抗震设计人员提供参考。 相似文献
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The lithospheric structure of the Sinai Peninsula is shown by means of nine shear velocity profiles for depths ranging from
zero to 50 km, determined from the Rayleigh wave analysis. The traces of 30 earthquakes, which occurred from 1992 to 1999
in and around the study area, have been used to obtain Rayleigh wave dispersion. These earthquakes were registered by a broadband
station located in Egypt (KEG station). The dispersion curves were obtained for periods between 3 and 40 s, by digital filtering
with a combination of MFT and TVF filtering techniques. After that, all seismic events were grouped in source zones to obtain
a dispersion curve for each source-station path. These dispersion curves were inverted according to generalized inversion
theory, to obtain shear wave velocity models for each source-station path, which is the main goal of this study. The shear
velocity structure obtained for the Sinai Peninsula is shown through the shear velocity distributions with depth. These results
agree well with the geology and other geophysical results, previously obtained from seismic and gravity data. The obtained
velocity models suggest the existence of lateral and vertical heterogeneity. The shear velocity increases generally with depth
for all paths analyzed in the study area. Nevertheless, in some paths a small low velocity channel in the upper or lower crust
occurs. Along these profiles, it is found that the crustal structure of the Sinai Peninsula consists of three principal layers:
upper crust with a sedimentary layer and lower crust. The upper crust has a sedimentary cover of 2 km thick with an average
S-velocity of 2.53 km/s. This upper crust has a variable thickness ranging from 12 to 18 km, with S-wave velocity ranging
from 3.24 to 3.69 km/s. The Moho discontinuity is located at a depth of 30 km, which is reflected by a sharp increase in the
S-velocity values that jump from 3.70–4.12 to 4.33–4.61 km/s. 相似文献
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基于饱和两相介质弹性波动方程分析SV波在饱和土体自由表面的反射问题,引入波动方程的势函数解答,求解出二维问题中SV波入射情况下饱和土体自由场的位移、速度、加速度和应力响应。在饱和土体自由场响应解析解基础上,建立SV波入射下饱和土体自由场静、动力有限元模型。建模中考虑了如下几方面因素:(1)在不同分析步,对土体单元赋予不同材料本构。通过*model change命令进行单元生死设定,从而实现在初始应力场平衡的静力状态下采用DuncanChang本构模型,而地震波动输入时采用Davidenkov动力本构模型;(2)采用多孔介质黏弹性人工边界条件,在人工边界上分别施加固相和液相介质的弹簧和阻尼来模拟饱和土体中能量的传播;(3)将地震波转化为作用在人工边界上的等效地震荷载,施加到人工边界节点上;(4)土体单元采用4结点平面应变孔压单元(CPE4P)。有限元计算与解析解比较结果表明:SV波在垂直入射和掠入射时,竖向位移响应为零;在45°左右入射时,水平位移响应最大;60°左右入射时,竖向位移响应最大。这些结论与解析解吻合较好,本文模型为建立土-结构动力相互作用模型打下良好的基础。 相似文献