横向非均匀介质中弹性地震波传播的数值模拟     

张剑峰  李幼铭 《地震工程与工程振动》1995,15(3):21-31

应用混合变量弹性动力学方程和线性常微分方程组的矩阵指数解法，将层状介质中广泛应用的弹性波传播矩阵解法推广至横向非均匀介质，给出了一种可计算复杂地质体中弹性波传播的广义传播矩阵数值解法。该方法可模拟任意震源及所产生的各种体波、面波，数值结果表明具有很高的计算精度。  相似文献   

大气传播延迟改正在GAMIT软件中的应用   总被引：4，自引：1，他引：3       下载免费PDF全文

张清志 《沉积与特提斯地质》2001,21(2):23-30

卫星信号从GPS卫星发射到地面的过程中经过了以充满大气为介质的空间,电磁波在这种变化的介质中传播,其传播的方向、速度、强度都可能随时改变,本文简略地介绍了大气传播延迟的产生及其对GPS测量的影响,并就GAMIT软件对大气传播延迟的控制方法和所采用的改正模型做一简单介绍,并对减弱和消除大气传播延迟的方法和手段进行了讨论。  相似文献   

Run-up from impact tsunami     

D. G. Korycansky  Patrick J. Lynett 《Geophysical Journal International》2007,170(3):1076-1088

We report on calculations of the on-shore run-up of waves that might be generated by the impact of subkilometre asteroids into the deep ocean. The calculations were done with the COULWAVE code, which models the propagation and shore-interaction of non-linear moderate- to long-wavelength waves  ( kh < π)  using the extended Boussinesq approximation. We carried out run-up calculations for several different situations: (1) laboratory-scale monochromatic wave trains onto simple slopes; (2) 10–100 m monochromatic wave trains onto simple slopes; (3) 10–100 m monochromatic wave trains onto a compound slope representing a typical bathymetric profile of the Pacific coast of North America; (4) time-variable scaled trains generated by the collapse of an impact cavity in deep water onto simple slopes and (5) full-amplitude trains onto the Pacific coast profile. For the last case, we also investigated the effects of bottom friction on the run-up. For all cases, we compare our results with the so-called 'Irribaren scaling': The relative run-up   R / H ₀=ξ= s ( H ₀/ L ₀)^−1/2  , where the run-up is   R , H ₀  is the deep-water waveheight, L ₀ is the deep-water wavelength, s is the slope and ξ is a dimensionless quantity known as the Irribaren number. Our results suggest that Irribaren scaling breaks down for shallow slopes   s ≤ 0.01  when  ξ < 0.1 − 0.2  , below which   R / H ₀  is approximately constant. This regime corresponds to steep waves and very shallow slopes, which are the most relevant for impact tsunami, but also the most difficult to access experimentally.  相似文献   

Lamb's problem with the lattice model Mka3D     

C. Mariotti 《Geophysical Journal International》2007,171(2):857-864

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High-resolution structures of the Landers fault zone inferred from aftershock waveform data   总被引：2，自引：0，他引：2  

Hongyi Li  Lupei Zhu  Hongfeng Yang 《Geophysical Journal International》2007,171(3):1295-1307

High-frequency body waves recorded by a temporary seismic array across the surface rupture trace of the 1992 Landers, California, earthquake were used to determine fault-zone structures down to the seismogenic depth. We first developed a technique to use generalized ray theory to compute synthetic seismograms for arbitrarily oriented tabular low-velocity fault-zone models. We then generated synthetic waveform record sections of a linear array across a vertical fault zone. They show that both arrival times and waveforms of P and S waves vary systematically across the fault due to transmissions and reflections from boundaries of the low-velocity fault zone. The waveform characteristics and arrival-time patterns in the record sections allow us to locate the boundaries of the fault zone and to determine its P - and S -wave velocities independently as well as its depth extent. Therefore, the trade-off between the fault-zone width and velocities can be avoided. Applying the method to the Landers waveform data reveals a low-velocity zone with a width of 270–360 m and a 35–60 per cent reduction in P and S velocities relative to the host rock. The analysis suggests that the low-velocity zone extends to a depth of ∼7 km. The western boundary of the low-velocity zone coincides with the observed main surface rupture trace.  相似文献   

Analysis of kinematic seismic response of tapered piles   总被引：2，自引：0，他引：2  

Mahmoud Ghazavi 《Geotechnical and Geological Engineering》2007,25(1):37-44

In the present work, a two-phase analysis is used to assess the lateral movement of a tapered pile due to kinematic seismic loading resulted from earthquakes. First, the free-field horizontal displacement of the ground due to earthquake is estimated using available theory of wave propagation. Second, these estimated soil movements are imposed on the taper pile in a closed-form solution to compute the pile response. The governing differential equation for an arbitrary pile segment is obtained, which includes the free-field horizontal movement estimated from the first phase. The equation is solved explicitly to obtain the horizontal deflection. Parametric studies show that tapered piles tend to be more flexible than uniform piles of the same volume and length under earthquake loading, which is soundly interesting.  相似文献   

Gaussian beams in inhomogeneous media: A review     

Yu. A. Kravtsov  P. Berczynski 《Studia Geophysica et Geodaetica》2007,51(1):1-36

The paper outlines the most important results of the paraxial complex geometrical optics (CGO) in respect to Gaussian beams diffraction in the smooth inhomogeneous media and discusses interrelations between CGO and other asymptotic methods, which reduce the problem of Gaussian beam diffraction to the solution of ordinary differential equations, namely: (i) Babich’s method, which deals with the abridged parabolic equation and describes diffraction of the Gaussian beams; (ii) complex form of the dynamic ray tracing method, which generalizes paraxial ray approximation on Gaussian beams and (iii) paraxial WKB approximation by Pereverzev, which gives the results, quite close to those of Babich’s method. For Gaussian beams all the methods under consideration lead to the similar ordinary differential equations, which are complex-valued nonlinear Riccati equation and related system of complex-valued linear equations of paraxial ray approximation. It is pointed out that Babich’s method provides diffraction substantiation both for the paraxial CGO and for complex-valued dynamic ray tracing method. It is emphasized also that the latter two methods are conceptually equivalent to each other, operate with the equivalent equations and in fact are twins, though they differ by names. The paper illustrates abilities of the paraxial CGO method by two available analytical solutions: Gaussian beam diffraction in the homogeneous and in the lens-like media, and by the numerical example: Gaussian beam reflection from a plane-layered medium.  相似文献   

论防震减灾科普宣传与培训教育工作     

孙国学  孙晶岩 《山西地震》2007,(4):34-36,39

文章从如何做好防震减灾科普知识的宣传与培训教育工作,提高群众在地震发生时的自救、互救能力和抢险救灾能力等方面进行了论述,并提出了相应的想法和建议。对切实提高社会公众防灾减灾的能力、普及防震减灾知识有一定的参考价值。  相似文献   

Fault propagation and climatic control of sedimentation on the Ghoubbet Rift Floor: insights from the Tadjouraden cruise in the western Gulf of Aden     

L. Audin  I. Manighetti  P. Tapponnier  F. Métivier  E. Jacques  P. Huchon 《Geophysical Journal International》2001,144(2):391-413

A detailed geophysical survey of the Ghoubbet Al Kharab (Djibouti) clarifies the small-scale morphology of the last submerged rift segment of the propagating Aden ridge before it enters the Afar depression. The bathymetry reveals a system of antithetic normal faults striking N130°E, roughly aligned with those active along the Asal rift. The 3.5 kHz sub-bottom profiler shows how the faults cut distinct layers within the recent, up to 60 m thick, sediment cover on the floor of the basin. A large volcanic structure, in the centre of the basin, the 'Ghoubbet' volcano, separates two sedimentary flats. The organization of volcanism and the planform of faulting, with en echelon subrifts along the entire Asal–Ghoubbet rift, appear to confirm the westward propagation of this segment of the plate boundary. Faults throughout the rift have been active continuously for the last 8400 yr, but certain sediment layers show different offsets. The varying offsets of these layers, dated from cores previously retrieved in the southern basin, imply Holocene vertical slip rates of 0.3–1.4 mm yr⁻¹ and indicate a major decrease in sedimentation rate after about 6000 yr BP, and a redistribution of sediments in the deepest troughs during the period that preceded that change.  相似文献   

Wavefront healing: a banana–doughnut perspective     

S.&#;H. Hung  F. A. Dahlen  Guust Nolet 《Geophysical Journal International》2001,146(2):289-312

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