Comparison of two great Chile tsunamis in 1960 and 2010 using numerical simulation

Great differences in hazard and losses were shown from two tsunamis, both generated in Chile, one in 1960 and the other in 2010. Numerical simulation was applied to the tsunami analysis. The fault dislocation of the seafloor was assumed to equal to the initial tsunami wave field, which can be calculated by the formula of fault dislocation in the elastic isotropic half-space. The linear long wave theory was used as the tsunami hydrodynamic model, and the finite difference method and leap-frog scheme were selected for solving the equations. The accuracy of the simulated results was verified by the observed data in five tide gauges. By means of two scenario tsunamis, the analytical results show that the earthquake magnitude, bathymetry in rupture zone and rapid release of warning information in 2010 tsunami are the main explanations of the aforementioned great difference.     

海啸在冲绳海槽和东海浅水大陆架地形上产生和传播的数值模拟

运用数值模拟的方法对在冲绳海槽产生9.0级地震,并引发海啸的过程和海啸波在东海浅水大陆架地形上的传播过程进行研究.模拟的结果表明,数值模拟产生的波浪符合海啸波的特点,东海浅水大陆架适合海啸波的传播.     

Comparison of laboratory-scale solute transport visualization experiments with numerical simulation using cross-bedded sandstone

Using a slab of Massillon Sandstone, laboratory-scale solute tracer experiments were carried out to test numerical simulations using the Advection–Dispersion Equation (ADE). While studies of a similar nature exist, our work differs in that we combine: (1) experimentation in naturally complex geologic media, (2) X-ray absorption imaging to visualize and quantify two-dimensional solute transport, (3) high resolution transport property characterization, with (4) numerical simulation. The simulations use permeability, porosity, and solute concentration measured to sub-centimeter resolution. While bulk breakthrough curve characteristics were adequately matched, large discrepancies exist between the experimental and simulated solute concentration fields. Investigation of potential experimental errors suggests that the failure to fit solute concentration fields may lie in loss of intricate connectivity within the cross-bedded sandstone occurring at scales finer than our property characterization measurements (i.e., sub-centimeter).     

1960年智利Mw9.5级大震的讨论

讨论了1960年智利‰9．5级地震的位置特点和发生年份特点。将此震与2004年印度尼西亚Mw9．0级地震作了对比,发现有类似之处,即它们的位置皆位于深海沟端部相对变浅的地段。另外,其附近早期的大震活动与这两次9级以上大震的发生年份有韵律性相关。     

2010年智利地震海啸数值模拟及其对我国沿海的影响分析

2010年2月27日06时34分(北京时间14时34分),在智利中南部近岸(36.1°S, 72.6°W)发生Mw8.8级地震,并引发了泛太平洋范围的海啸,太平洋沿岸多个国家的验潮站和海啸监测浮标均监测到了强震引发的海啸;海啸波传播25 h后到达我国沿海.本文利用海啸数值模型对此次地震海啸进行了数值模拟.重点模拟了我国沿海及智利周边区域海啸波的传播特征,结果与观测数据拟合良好.通过对数值模拟结果的分析,定量阐述了智利海啸对我国沿海地区的影响,给出了此次海啸对我国沿海各海区的危险性分布.     

Comparison of the 2010 Chile and 2011 Japan Tsunamis in the Far Field

In this study we analyze water level data from coastal tide gauges and deep-ocean tsunameters to explore the far-field characteristics of two major trans-Pacific tsunamis, the 2010 Chile and the 2011 Japan (Tohoku-oki) events. We focused our attention on data recorded in California (14 stations) and New Zealand (31 stations) as well as on tsunameters situated along the tsunami path and proximal to the study sites. Our analysis considers statistical analyses of the time series to determine arrival times of the tsunami as well as the timing of the largest waves and the highest absolute sea levels. Fourier and wavelet analysis were used to describe the spectral content of the tsunami signal. These characteristics were then compared between the two events to highlight similarities and differences between the signals as a function of the receiving environment and the tsunami source. This study provides a comprehensive analysis of far-field tsunami characteristics in the Pacific Ocean, which has not experienced a major tsunami in nearly 50 years. As such, it systematically describes the tsunami response characteristics of modern maritime infrastructure in New Zealand and California and will be of value for future tsunami hazard assessments in both countries.     

The landslides and tsunamis of the 30th of December 2002 in Stromboli analysed through numerical simulations

On the 30th of December 2002 two tsunamis were generated only 7 min apart in Stromboli, southern Tyrrhenian Sea, Italy. They represented the peak of a volcanic crisis that started 2 days before with a large emission of lava flows from a lateral vent that opened some hundreds of meters below the summit craters. Both tsunamis were produced by landslides that detached from the Sciara del Fuoco. This is a morphological scar and is the result of the last collapse of the northwestern flank of the volcanic edifice, that occurred less than 5 ka b.p. The first tsunami was due to a submarine mass movement that started very close to the coastline and that involved about 20×10⁶ m³ of material. The second tsunami was engendered by a subaerial landslide that detached at about 500 m above sea level and that involved a volume estimated at 4–9×10⁶ m³. The latter landslide can be seen as the retrogressive continuation of the first failure. The tsunamis were not perceived as distinct events by most people. They attacked all the coasts of Stromboli within a few minutes and arrived at the neighbouring island of Panarea, 20 km SSW of Stromboli, in less than 5 min. The tsunamis caused severe damage at Stromboli.In this work, the two tsunamis are studied by means of numerical simulations that use two distinct models, one for the landslides and one for the water waves. The motion of the sliding bodies is computed by means of a Lagrangian approach that partitions the mass into a set of blocks: we use both one-dimensional and two-dimensional schemes. The landslide model calculates the instantaneous rate of the vertical displacement of the sea surface caused by the motion of the underwater slide. This is included in the governing equations of the tsunami, which are solved by means of a finite-element (FE) technique. The tsunami is computed on two different grids formed by triangular elements, one covering the near-field around Stromboli and the other also including the island of Panarea.The simulations show that the main tsunamigenic potential of the slides is restricted to the first tens of seconds of their motion when they interact with the shallow-water coastal area, and that it diminishes drastically in deep water. The simulations explain how the tsunamis that are generated in the Sciara del Fuoco area, are able to attack the entire coastline of Stromboli with larger effects on the northern coast than on the southern. Strong refraction and bending of the tsunami fronts is due to the large near-shore bathymetric gradient, which is also responsible for the trapping of the waves and for the persistence of the oscillations. Further, the first tsunami produces large waves and runup heights comparable with the observations. The simulated second tsunami is only slightly smaller, though it was induced by a mass that is approximately one third of the first. The arrival of the first tsunami is negative, in accordance with most eyewitness reports. Conversely, the leading wave of the second tsunami is positive.     

Focal process of the great Chilean earthquake May 22, 1960

Long-period strain seismogram recorded at Pasadena is used to determine the focal process of the 1960 Chilean earthquake. Synthetic seismograms computed for various fault models are matched with the observed strain seismogram to determine the fault parameters. A low-angle (～ 10°) thrust model with rupture length of 800 km and rupture velocity of 3.5 km/sec is consistent with the observed Rayleigh/Love wave ratio and the radiation asymmetry. A seismic moment of 2.7 · 10³⁰ dyn · cm is obtained for the main shock. This value, together with the estimated fault area of 1.6 · 10⁵ km², gives an average dislocation of 24 m. The strain seismogram clearly shows unusually long-period (300–600 sec) wave arriving at the P time of a large foreshock which occurred about 15 minutes before the main shock, suggesting a large slow deformation in the epicentral area prior to the major failure. A simple dislocation model shows that a dislocation of 30 m, having a time constant of 300–600 sec, over a fault plane of 800 × 200 km² is required to explain this precursory displacement. The entire focal process may be envisaged in terms of a large-scale deformation which started rather gradually and eventually triggered the foreshocks and the “main” shock. This mechanism may explain the large premonitory deformations documented, but not recorded instrumentally, for several Japanese earthquakes. The moments of the main shock and the precursor add to 6 · 10³⁰ dyn · cm which is large enough to affect the earth's polar motion.     

张量CSAMT有效观测区域模拟对比分析

根据标量CSAMT、垂直双偶极源CSAMT、三偶极源CSAMT等多分量响应式设计程序,通过数值模拟给出其十字型场源的X方向和Y方向电偶极子电磁场各分量的场值分布图,发现十字型观测区域中存在着分布零散且较广的弱区,有效观测区域较小,且对地形条件要求苛刻,不利于在山区等地形起伏复杂地区施工.在旋转三偶极装置的原理基础上提出了多偶极子源矢量合成测量方式,相比较十字型场源的施工方式而言,通过矢量合成多组的电偶极子,有利于实现全区无弱区观测,同时场源铺设简便对各种地形有着较强的适用性.研究结果为张量可控源进一步的测量工作提供技术依据.

     

考虑SSI效应的隔震结构体系振动台模型试验与数值模拟对比研究

基于考虑土-结构相互作用(SSI)效应的隔震结构体系振动台模型试验,以ABAQUS软件为计算平台,考虑土体的非线件特性,建立了将土体一桩基-隔震结构视为共同工作整体的三维有限元模型,对各种试验工况下的地震反应进行了数值模拟计算,并与试验结果进行了对比分析,结果表明:数值模拟和振动台模型试验结果基本一致,两者得到的SSI效应对隔震结构地震反应的影响体现出相似的规律性,印证了数值模型的正确性.     

Mercury dynamic simulation of Minamata Bay by using a three-dimensional numerical model

Ocean Dynamics - Residual mercury dynamic has been the research emphasis since mercury contamination was publicly recognized in Minamata Bay. Simulation of mercury distribution and transport...     

Two-dimensional numerical simulation of sediment transport using improved critical shear stress methods

Research on the critical shear stresses for erosion and deposition for cohesive sediment has attracted substantial attention from both engineering and theoretical viewpoints due to their importance in sediment transport theory.Previous studies have proposed a large number of empirical and semiempirical methods to estimate the critical erosion and deposition shear stress,but comparative analyses and validation of the existing methods are still lacking,leaving questions regarding the applicability...     

利用数值模拟方法研究宏观丹霞地貌坡地的演化过程

由于红层岩性、节理发育状态、年代、构造运动特征、气候以及区域地质地理条件等的不同,丹霞地貌的形态在区域上有很大差别,其成因机制十分复杂.从丹霞地貌演化机制的宏观意义着眼,考虑岩性、节理、构造抬升速率及降雨等因素,基于地貌演化理论,利用数值模拟方法定量地展现了丹霞地貌坡地在构造抬升及流水侵蚀这两个主要的内外力作用下的动力学演化过程.地貌演化的幼年期和壮年期,流域输沙能力相对较大,主要表现为流水对基岩的侵蚀过程;直至演化的老年期,流域输沙能力相对较小,大量的风化物淤积,坡度变缓.同时,对不同岩性和垂直节理深度的计算结果进行了对比分析,砾石质地相对坚硬,计算得到的高程较大,表明岩性硬度越高,较容易形成陡壁,而岩性较软,易形成丘陵.垂直节理深度不同,坡地峰值几乎相同,但浅垂直节理较深垂直节理的谷值大,表明流水沿垂直节理进行下切侵蚀的程度不同,对景观的形成有着重要影响.数值模拟结果在物理上是合理的,有利于进一步定性地认识到岩层岩性、节理、构造抬升及流水侵蚀对丹霞地貌坡地演化的作用.     

Parallel numerical simulation of two-phase flow model in porous media using distributed and shared memory architectures

A two-phase (water and oil) flow model in a homogeneous porous media is studied, considering immiscible and incompressible displacement. This model is numerically solved using the Finite Volume Method (FVM) and we compare four numerical schemes for the approximation of fluxes on the faces of the discrete volumes. We describe briefly how to obtain the mathematical and computational models applying axiomatic formulations and generic programming. Two strategies of parallelization are implemented in order to reduce the execution time. We study distributed (cluster of CPUs) and shared (Graphics Processing Units) memory architectures. A performance comparison of these two architectures is done along with an analysis of the four numerical schemes, for a water-flooding five-spot pattern model.     

数值模拟在地球动力学中的研究进展

本文主要针对有限单元法,对近10几年来数值模拟在地球动力学中的应用和发展作了回顾,分为构造应力场模拟;地幔热对流模拟;板块碰撞模拟;岩石圈流变学模拟;以及地震机制与预测模拟等部分.简单阐述了当前地球动力学数值模拟的发展趋势并论述了其面临的主要问题.     

震后短期和长期形变模拟——以1960年智利Mw9.5地震为例

以1960年5月智利瓦尔迪维亚(Valdivia)Mw9.5地震为例分析震后不同时期的形变,实现了以Burgers体为粘弹介质模型来模拟震后粘弹松弛效应有限元数值模拟.计算结果表明,该粘弹介质模型可以模拟地震引起的瞬时同震弹性响应及震后粘弹松弛的短期和长期响应.由1960智利Mw9.5地震震后模拟的应变率显示以Burgers体为粘弹介质模型可以解决Maxwell体在模拟震后短期和长期形变不协调问题.     

起伏地形下各向异性的2D大地电磁无网格法数值模拟

作为一种基于节点的计算方法,无网格法具有构造高阶导数方便,自适应分析便利的优点,特别适合复杂地质构造的数值模拟.本文针对实际地球物理勘探中存在的起伏地形和各向异性的地电结构,提出用无网格法来模拟大地电磁响应,采用复合二次径向基函数构造了形函数,推导了大地电磁无网格法等价线性方程组,研究了系数矩阵的压缩存储方法以及大型稀疏复线性方程组快速求解算法,实现了起伏地形下各向异性的2D大地电磁高精度数值模拟.基于层状模型验证了算法的正确性,计算结果表明：无论是TM模式还是TE模式,计算相对误差均小于1%;通过对地垒和地堑模型的模拟,得出了起伏地形对视电阻率和相位的影响规律;对起伏地形下含有不同各向异性系数异常体的模型进行了数值模拟,为开展复杂地质结构的电磁场特征研究以及地形校正奠定了理论基础.随着计算科学的快速发展,无网格法必将成为新的高精度电磁场数值模拟方法.     

Substructure shake table test method using a controlled mass: formulation and numerical simulation

This study proposes a new substructure shake table test method that allows for experimental investigation of the lower portion of structures while the upper part is numerically analyzed. Compatibility conditions are derived to ensure that the dynamic characteristics of the substructured system are equivalent to the reference entire structure. This method utilizes controlled masses to incorporate interface forces from the computational substructure to the experimental substructure. A feasible implementation procedure for the interface force compatibility is developed using a series of conversions and signal processing. For validation of the capabilities and limitations of the proposed substructure method, numerical simulations are performed using detailed models including dynamics of the controlled mass systems. Results from the numerical simulations showed that the proposed substructure method produced comparable results to the reference entire simulations. The average error between top floor displacements produced by substructured and entire responses for earthquake inputs was 7.1%. Numerical studies showed that the substructure method has potential to serve as an alternative to shaking table tests of entire structures. Copyright © 2012 John Wiley & Sons, Ltd.     

Comparison of drought projections using two UK weather generators

Abstract

Possible changes in drought under future climate scenarios may pose unprecedented challenges for water resources, as well as other environmental and societal issues, and need assessment to quantify their associated risk. Two weather generators, based upon (a) the Neyman-Scott Rectangular Pulses (NSRP) model as implemented by the United Kingdom Climate Projections 09 (UKCP09) study, and (b) the generalized linear model (GLM) approach, are used to investigate potential variations in drought conditions for six catchments in the UK under climate projections. The results show that both weather generators provide rainfall simulations having satisfactory monthly statistics. However, the rainfall series from the UKCP09 weather generators lack inter-annual variability, whereas the GLM simulations, which include non-stationary global circulation model (GCM) outputs as driving variables, seem to have a more appropriate representation of the observed drought conditions. For drought projections in the 2080s, the UKCP09 simulations provide repetitive patterns without much temporal variation, similar to the results in the control period. This study suggests that for the drought index considered here (a 3-month drought severity index) the GLM approach appears to be a more appropriate model for drought study on inter-annual scales in comparison with the UKCP09 weather generator.

Editor D. Koutsoyiannis

Citation Chun, K.P., Wheater, H.S., and Onof, C., 2013. Comparison of drought projections using two UK weather generators. Hydrological Sciences Journal, 58 (2), 295–309.