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1.
Harry H. Yeh 《Natural Hazards》1991,4(2-3):209-220
Nearshore behaviors of tsunamis, specifically those formed as a single uniform bore, are investigated experimentally in a laboratory environment. The transition process from tsunami bore to runup is described by the momentum exchange process between the bore and the small wedge-shaped water body along the shore: the bore front itself does not reach the shoreline directly, but the large bore mass pushes the small, initially quiescent water in front of it. The fluid motions near the runup water line appear to be complex. The complex flow pattern must be caused by irregularities involved in the driving bore and turbulence advected into the runup flow. Those experimental results suggest that the tsunami actions at the shoreline involve significant mean kinetic energy together with violent turbulence. Even though the behaviors of bore motion were found to be different from those predicted by the shallow-water wave theory, the maximum runup height appears to be predictable by the theory if the value of the initial runup velocity is modified (reduced). Besides the friction effect, this reduction of the initial runup velocity must be related to the transition process as well as the highly interacting three-dimensional runup motion. 相似文献
2.
Distribution Functions of Tsunami Wave Heights 总被引：1，自引：1，他引：1
The problem of describing the distribution functions of tsunami wave heights is discussed. Data on runup heights obtained in field surveys of several tsunamis for the last decade are used to calculate the empirical distribution functions. It is shown that the log-normal distribution describes the observed data well. This means that the irregular topography and coastline are major factors which influence the height distribution. The power distribution related with the geometric decay of the propagated wave is a good approximation for one event (Sulawesi, January 1, 1996) only. Results of a numerical simulation of the tsunami event in the Japan (East) Sea on July 12, 1993 are presented. It is shown that the computed wave height distribution, obtained by using the runup correction in the framework of nonlinear shallow-water theory, is in good agreement with the observed height distribution. Simulations are used to study the transformation of the distribution function on different distances from the source. 相似文献
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4.
K. V. S. R. Prasad S. V. V. Arun Kumar Ch. Venkata Ramu P. Sreenivas 《Natural Hazards》2009,49(2):347-360
The nearshore parameters, viz., wave runup, wave setup, and wave energy have been estimated during storm and normal conditions
of SW monsoon (June–September) and NE monsoon (November–February) by empirical parameterization along Visakhapatnam coast.
These results were compared with the field observations during three storms of SW monsoon season in the year 2007. The higher
nearshore wave energies were observed at R.K. Beach, Jodugullapalem beach, and Sagarnagar beach during both the seasons. During
storm events, the higher wave energies associated with higher wave runups cause severe erosion along the wave convergence
zones. The storm wave runups (SWRUs) were higher at R.K. Beach, Palm beach, Jodugullapalem beach, and Sagarnagar Beach. The
yearly low wave energy was observed at Lawson’s Bay with lowest wave runup, considered as safest zone. R.K. Beach, Palm beach,
and Jodugullapalem beach are identified as vulnerable zones of wave attack. It is noteworthy that in addition to wave energies,
wave runups and wave setups also play a vital role in endangering the coast. 相似文献
5.
STEIN BONDEVIK JOHN INGE SVENDSEN GEIR JOHNSEN JAN MANGERUD PETER EMIL KALAND 《Boreas: An International Journal of Quaternary Research》1997,26(1):29-53
The statigraphy in 25 coastal lakes shows that most of the Norwegian coastline was impacted by a large tsunami about 7200 14 C BP. The methodology has been to core a staircase of lake basins above the contemporary sea level in several areas and to map the tsunami deposit to its maximum elevation. The tsunami was identified in the sedimentary record as an erosional unconformity overlain by graded or massive sand with shell fragments, followed by redeposited organic detritus. The greatest recorded runup along the coast (10–11 m above high tide) is found in areas most proximal to the Storegga slide scar on the Norwegian continental slope (Sunnmøre). To the north and south, runup is less, about 6–7 m at Bjugn (250 km north of Sunnmøre) and about 3–5 m in Austrheim (200 km to the south of Sunnmerre). This runup pattern supports the suggestion that the tsunami was generated by the Second Storegga Slide. The recorded runup heights are consistent within and between the investigated areas, and imply that the tsunami wave was not significantly influenced by the local topography, suggesting a very long wave length. The mapped runup estimates are in good agreement with a numerical model of the tsunami generated by the Second Storegga slide, and indicate that the slide was a single major event rather than a set of smaller slides. 相似文献
6.
Lu Sun 《国际地质力学数值与分析法杂志》2003,27(1):69-84
A closed‐form deflection response of a beam rest is presented in this paper using the integral transform method. The theory of linear partial differential equations is used to represent the deflection of beam subjected to a moving harmonic line load in integration form. The solution is finally carried out using the inverse Fourier transform. To evaluate the integration analytically, poles of the integrand are identified with the help of algebraic equation theory. Residue theorem is then utilized to represent the integration as a contour integral in the complex plane. Closed‐form deflections and numerical results are provided for different combinations of load frequency and velocity. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
7.
基于有限体积方法和结构化网格,建立了海底滑坡引起的波浪传播数值模型。模型控制方程为考虑了海床随时间变化的二维浅水方程。采用中心迎风格式计算控制体界面数值通量,采用线性重构技术、局部海床高程处理技术和全隐式离散底摩阻项,保证了格式的和谐性、守恒性和水深非负性,有效处理了海岸动边界问题。时间积分采用具有强稳定性质的二阶龙格-库塔方法（ssp RK）。针对滑坡体兴波经典算例开展数值模拟,将计算结果与解析解、实验结果及其他模型计算结果进行比较和分析。结果表明,对于所考虑的计算工况,模型能较合理地模拟滑坡兴波的产生、传播和爬高过程。 相似文献
8.
Probabilistic Analysis of Tsunami Hazards* 总被引：2，自引：1，他引：2
Determining the likelihood of a disaster is a key component of any comprehensive hazard assessment. This is particularly true
for tsunamis, even though most tsunami hazard assessments have in the past relied on scenario or deterministic type models.
We discuss probabilistic tsunami hazard analysis (PTHA) from the standpoint of integrating computational methods with empirical
analysis of past tsunami runup. PTHA is derived from probabilistic seismic hazard analysis (PSHA), with the main difference
being that PTHA must account for far-field sources. The computational methods rely on numerical tsunami propagation models
rather than empirical attenuation relationships as in PSHA in determining ground motions. Because a number of source parameters
affect local tsunami runup height, PTHA can become complex and computationally intensive. Empirical analysis can function
in one of two ways, depending on the length and completeness of the tsunami catalog. For site-specific studies where there
is sufficient tsunami runup data available, hazard curves can primarily be derived from empirical analysis, with computational
methods used to highlight deficiencies in the tsunami catalog. For region-wide analyses and sites where there are little to
no tsunami data, a computationally based method such as Monte Carlo simulation is the primary method to establish tsunami
hazards. Two case studies that describe how computational and empirical methods can be integrated are presented for Acapulco,
Mexico (site-specific) and the U.S. Pacific Northwest coastline (region-wide analysis).
* The U.S. Government’s right to retain a non-exclusive, royalty-free license in and to any copyright is acknowledged. 相似文献
9.
Spectral simulation of multivariable stationary random functions using covariance fourier transforms 总被引：1，自引：0，他引：1
A coregionalization simulation consists of the generation of realizations of a group of spatially related random variables. The Fourier integral method is presented, modified to carry out such a multivariable simulation. This method allows the simulation of realizations with any specified symmetrical covariance matrix and it is not limited to the classic linear model of coregionalization. The results of gaussian nonconditinal simulations from a case study modeling the spatial characteristics of a layer of coal are given. 相似文献
10.
Tsunami runup and drawdown can cause liquefaction failure of coastal fine sand slopes due to the generation of high excess
pore pressure and the reduction of the effective over burden pressure during the drawdown. The region immediately seaward
of the initial shoreline is the most susceptible to tsunami-induced liquefaction failure because the water level drops significantly
below the still water level during the set down phase of the drawdown. The objective of this work is to develop and validate
a numerical model to assess the potential for tsunami-induced liquefaction failure of coastal sandy slopes. The transient
pressure distribution acting on the slope due to wave runup and drawdown is computed by solving for the hybrid Boussinesq—nonlinear
shallow water equations using a finite volume method. The subsurface pore water pressure and deformation fields are solved
simultaneously using a finite element method. Two different soil constitutive models have been examined: a linear elastic
model and a non-associative Mohr–Coulomb model. The numerical methods are validated by comparing the results with analytical
models, and with experimental measurements from a large-scale laboratory study of breaking solitary waves over a planar fine
sand beach. Good comparisons were observed from both the analytical and experimental validation studies. Numerical case studies
are shown for a full-scale simulation of a 10-m solitary wave over a 1:15 and 1:5 sloped fine sand beach. The results show
that the soil near the bed surface, particularly along the seepage face, is at risk to liquefaction failure. The depth of
the seepage face increases and the width of the seepage face decreases with increasing bed slope. The rate of bed surface
loading and unloading due to wave runup and drawdown, respectively, also increases with increasing bed slope. Consequently,
the case with the steeper slope is more susceptible to liquefaction failure due to the higher hydraulic gradient. The analysis
also suggests that the results are strongly influenced by the soil permeability and relative compressibility between the pore
fluid and solid skeleton, and that a coupled solid/fluid formulation is needed for the soil solver. Finally, the results show
the drawdown pore pressure response is strongly influenced by nonlinear material behavior for the full-scale simulation. 相似文献
11.
12.
The storm impact scale of Sallenger (J Coast Res 890–895, 2000) was tested on a partially engineered beach. This scale is supposed to provide a convenient tool for coastal managers to categorize the storm impact at the shore. It is based on the relation between the elevation of storm wave runup and the elevation of a critical geomorphic or man-made structures in the present study. Two different approaches were tested to estimate the elevation of extreme storm wave runup: (1) a parametric model based on offshore wave conditions and local beach slope and (2) the XBeach process-based model that solves implicitly the runup. The study shows comparisons between impact regimes computed with the two methods and those derived from video observations acquired during 2 weeks while the site was battered by three consecutive storms. Storms scenario including wave conditions with higher return periods and different tidal range were also investigated. The advantages and disadvantages of the two methods used to compute extreme water level are then compared, and guidelines for the development of early warning system are drawn. 相似文献
13.
Abnormal tsunami amplification and runup in narrow bays is studied with respect to the Samoa tsunami of 29 September 2009. The data of the tide gauge in Pago Pago harbour are used to calculate wave runup in the city of Pago Pago (Tutuila, American Samoa) for two approximations of the bottom topography: a plane beach and a narrow bay. Theoretical estimates of tsunami runup are compared with field survey data for the 2009 Samoa tsunami. It is shown that both formulations result in equally good estimates of runup, having approximately the same difference with the field measurements. However, the narrow bay model presents more wave amplification and, consequently, runup, which is the main observation of the field survey. The differences in estimated shoreline velocity, travel time and wave breaking regime, calculated in the framework of these two approximations, are also discussed. It is concluded that wave runup in narrow bays should be calculated by the corresponding formulas, which should be taken into account by tsunami early warning systems. 相似文献
14.
DAN MATSUMOTO HAJIME NARUSE SHIGEHIRO FUJINO APICHART SURPHAWAJRUKSAKUL THANAWAT JARUPONGSAKUL NORIHIKO SAKAKURA MASAFUMI MURAYAMA 《Sedimentology》2008,55(6):1559-1570
This study reveals the three‐dimensional morphology and syn‐sedimentary formation processes of a deformation structure termed ‘truncated flame structures’ which is found in a terrestrial tsunami deposit in southern Thailand that formed during the 2004 Indian Ocean Tsunami. The structure was found at the boundary between a lower fine‐grained layer and an upper coarse‐grained layer that are related to two runup events. In order to confirm the morphology of the structure, the authors excavated two trenches and an opencast pit. When viewed in a cross‐section oriented parallel to the direction of the runup current, the deformed boundary has an irregularly bulging profile, similar to that observed in flame structures. The protruding structures are inclined towards the downstream direction of the runup current, and are truncated horizontally along their upper surface by parallel laminations in the overlying layer. When viewed in a cross‐section oriented perpendicular to the current direction, it appears that parts of the upper layer descend into the lower layer as lobate masses. In places, these masses are completely detached from the main part of the upper layer, forming circular or elliptical shapes. The contact between the lower layer and the main part of the upper layer is a planar truncation surface. Opencast excavation of the contact surface revealed that the deformed structures have flat, sinuous horseshoe crests that open in a downstream direction. It is possible for the runup current to generate shear stress such that it deforms the boundary into a truncated flame structure. Moreover, the observations made in this study indicate the syn‐sedimentary development of the structure: deformation and truncation occurred simultaneously in association with the runup current that formed the upper layer. Truncated flame structures can be used as a criterion in identifying the syn‐sedimentary deformation of substrate: the structures are indicative of unidirectional flow with sufficiently high shear velocity to deform unconsolidated substrate. As in the present case, the truncated flame structures may be characteristic of tsunami events that involve strong unidirectional currents on land due to the extraordinarily long wave period of tsunamis, rather than other events such as storm surges or flooding. 相似文献
15.
目前隧道及大型地下工程往往在裂隙岩体中开挖,而裂隙与地下空间的距离及裂隙的扩展条件,制约着隧道及地下工程的稳定性。应用能考虑孔洞和裂纹问题的新型边界积分方程与无网格加辽金法结合,建立一种新型的边界无单元法。在该方法中基本的未知量是由边界上的面力和边界上位移密度函数构成的复变量边界函数 。文中应用的边界积分公式和Muskhelishvili的积分公式直接相关。将无网格构造方法引入新型的边界积分方程,建立了新型的边界无单元法。应用该方法详细分析了含隧道和裂纹间相互关系等问题,其数值结果与解析结果吻合很好,说明该方法的正确性和可行性。 相似文献
16.
By using the numerical method to model the ter-rain effect on the magnetotelluric field,few resultshave been obtained. The finite element method(FEM) was used by Chouteau and Bouchard (1988)and Wannamaker et al .(1986) ,andthe boundary el-ement method (BEM) was used by Xu and Zhou(1997) and Xu (1995) to model 2Dtopographyinflu-ences on magnetotelluric surveys . The BEM methodwas also used to model the 3Dtopographic effect onmagnetotelluric deep sounding (Xu et al .,1997 ;Xu,1995) .In t… 相似文献
17.
三维地形大地电磁场的边界元模拟方法 总被引：1，自引：0，他引：1
提出了一种用边界元法计算大地电磁场三维地形影响的数值模拟方法.首先用矢量积分理论和电磁场边界条件, 将上半空间(空气)和下半空间(地下介质)两个区域电磁场边值问题变为仅对地形界面的两个矢量面积分方程, 其中一个计算磁场, 称磁场方程; 另一个计算电场, 称电场方程.然后将对地形界面的积分剖分为一系列的三角单元积分.在三角单元积分中, 假设单元中电磁场为水平均匀大地空间电磁场与地形影响的迭加, 并假设地形影响为常项, 这样既保证了计算精度又使得计算方法简便.通过分解和计算, 每一个矢量面积分方程分解为对应3个坐标方向的3个常量线性方程, 这些线性方程组成了对角占优的线性方程组, 可用SSOR方法求解.文中给出了2个三维地形上大地电磁视电阻率曲线的计算结果. 相似文献
18.
In this paper, the frequency domain dynamic response of a pile embedded in a porous medium subjected to SH seismic waves is investigated. The surrounding porous medium of the pile is described by Biot’s poro-elastic theory, while the pile embedded in the porous medium is treated as a beam and described by a beam vibration theory. Using the Hankel transformation method, the fundamental solution for a half-space porous medium subjected to a horizontal circular patch load is established. According to the fictitious pile methodology, the second kind of Fredholm integral equation for the pile is established in terms of the obtained fundamental solution and free wave field. The solution of the integral equation yields the dynamic response of the pile to plane SH waves. Numerical results indicate that the parameters of the porous medium, the pile and incident waves have considerable influences on the dynamic response of the pile and the porous medium. 相似文献
19.
运用对偶积分方程来求解层状横观各向同性地基与墙下条形基础的共同作用问题。从直角坐标平面应变问题控制方程出发,通过傅里叶（Fourier）变换和层间连续性条件,可以得到层状横观各向同性地基的传递矩阵解。基于该传递矩阵解,并利用条形基础与地基接触的混合边值条件,推导出一组关于基础挠度和地基反力的对偶积分方程。考虑墙下条形基础受到竖向集中荷载的情况,利用弹性薄板理论先求解出条形基础挠度;随后应用雅可比（Jacobi）正交多项式和级数展开的方法,将对偶积分方程转化为线性代数方程组进行求解。编制了相应的计算程序,其计算结果与有限元软件ABAQUS的结果基本吻合,从而验证了所提理论的正确性。算例分析表明,板土相对刚度与地基成层性对地基反力、地表沉降和沿z轴竖向正应力有很大的影响。 相似文献
20.
P. C. Hsieh 《国际地质力学数值与分析法杂志》2006,30(12):1201-1212
In many instances soils can be assumed to behave like viscoelastic materials during loading/unloading cycles, and this study is aimed at setting up a viscoelastic model to investigate the dynamic response of a porous soil layer of finite thickness under the effect of periodically linear water waves. The waves and homogeneous water are described by potential theory and the porous material is described by a viscoelastic model, which is modified from Biot's poroelastic theory (1956). The distributions of pore water pressures and effective stresses of various soils such as silt, sand, and gravel are demonstrated by employing the proposed viscoelastic model. The discrepancies of the dynamic response between the simulations of viscoelastic model and elastic model are found to be strongly dependent on the wave frequency. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献