• Title/Summary/Keyword: seismic wave propagation

Search Result 111, Processing Time 0.024 seconds

Torsional wave in an inhomogeneous prestressed elastic layer overlying an inhomogeneous elastic half-space under the effect of rigid boundary

  • Kakar, Rajneesh
    • Earthquakes and Structures
    • /
    • v.9 no.4
    • /
    • pp.753-766
    • /
    • 2015
  • An investigation has been carried out for the propagation of torsional surface waves in an inhomogeneous prestressed layer over an inhomogeneous half space when the upper boundary plane is assumed to be rigid. The inhomogeneity in density, initial stress (tensile and compressional) and rigidity are taken as an arbitrary function of depth, where as for the elastic half space, the inhomogeneity in density and rigidity is hyperbolic function of depth. In the absence of heterogeneities of medium, the results obtained are in agreement with the same results obtained by other relevant researchers. Numerically, it is observed that the velocity of torsional wave changes remarkably with the presence of inhomogeneity parameter of the layer. Curves are compared with the corresponding curve of standard classical elastic case. The results may be useful to understand the nature of seismic wave propagation in geophysical applications.

Seismic Response Analysis of Dam-Reservoir System Using Hybrid Method (Hybrid 방법에 의한 댐-호소수 계 지진응답해석)

  • 김재관
    • Proceedings of the Earthquake Engineering Society of Korea Conference
    • /
    • 1998.04a
    • /
    • pp.163-170
    • /
    • 1998
  • The influence of the dam-reservoir interaction on the seismic response of dams is studied. The impounded water is assumed to be inviscid and compressible ideal fluid. Material damping is introduce to simulate the energy loss of wave propagation in the water. The irregular region of the impounded water adjacent to the dam is modeled by boundary element method. The regular region extending to infinity is modeled by the transmitting boundary. The dam body is assumed to behave elastically and modeled by finite element method. The coupled equation of motion is obtained by substructure method.

  • PDF

Investigation of Concrete Flaw Using Seismic First Arrival (탄성파 초동주시를 이용한 콘크리트 구조물의 결함 탐지)

  • 서백수;장선웅;김석현;서정희
    • Tunnel and Underground Space
    • /
    • v.11 no.2
    • /
    • pp.120-121
    • /
    • 2001
  • The purpose of this study is to investigate concrete flaw using seismic first arrival and various inversion method. Seismic wave propagation was calculated using finite element method in theoretical modelling and tomogram was made using various inversion methods in theoretical and experimental modelling. Five steps of seismic first arrival were selected from FEM results and these data were used to calculate seismic velocity section. According to the results, exact seismic first arrival picking method was proposed and experimental modelling was conducted.

  • PDF

Waveform inversion of shallow seismic refraction data using hybrid heuristic search method (하이브리드 발견적 탐색기법을 이용한 천부 굴절법 자료의 파형역산)

  • Takekoshi, Mika;Yamanaka, Hiroaki
    • Geophysics and Geophysical Exploration
    • /
    • v.12 no.1
    • /
    • pp.99-104
    • /
    • 2009
  • We propose a waveform inversion method for SH-wave data obtained in a shallow seismic refraction survey, to determine a 2D inhomogeneous S-wave profile of shallow soils. In this method, a 2.5D equation is used to simulate SH-wave propagation in 2D media. The equation is solved with the staggered grid finite-difference approximation to the 4th-order in space and 2nd-order in time, to compute a synthetic wave. The misfit, defined using differences between calculated and observed waveforms, is minimised with a hybrid heuristic search method. We parameterise a 2D subsurface structural model with blocks with different depth boundaries, and S-wave velocities in each block. Numerical experiments were conducted using synthetic SH-wave data with white noise for a model having a blind layer and irregular interfaces. We could reconstruct a structure including a blind layer with reasonable computation time from surface seismic refraction data.

Estimation of Wave Parameters for Probabilistic Tsunami Hazard Analysis Considering the Fault Sources in the Western Part of Japan (일본 서부 단층 지진원을 고려한 확률론적 지진해일 재해도 분석의 파고 변수 도출)

  • Rhee, Hyun-Me;Kim, Min Kyu;Sheen, Dong-Hoon;Choi, In-Kil
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.18 no.3
    • /
    • pp.151-160
    • /
    • 2014
  • Probabilistic tsunami hazard analysis (PTHA) is based on the approach of probabilistic seismic hazard analysis (PSHA) which is performed using various seismotectonic models and ground-motion prediction equations. The major difference between PTHA and PSHA is that PTHA requires the wave parameters of tsunami. The wave parameters can be estimated from tsunami propagation analysis. Therefore, a tsunami simulation analysis was conducted for the purpose of evaluating the wave parameters required for the PTHA of Uljin nuclear power plant (NPP) site. The tsunamigenic fault sources in the western part of Japan were chosen for the analysis. The wave heights for 80 rupture scenarios were numerically simulated. The synthetic tsunami waveforms were obtained around the Uljin NPP site. The results show that the wave heights are closely related with the location of the fault sources and the associated potential earthquake magnitudes. These wave parameters can be used as input data for the future PTHA study of the Uljin NPP site.

Time Domain Seismic Waveform Inversion based on Gauss Newton method (시간영역에서 가우스뉴튼법을 이용한 탄성파 파형역산)

  • Sheen, Dong-Hoon;Baag, Chang-Eob
    • 한국지구물리탐사학회:학술대회논문집
    • /
    • 2006.06a
    • /
    • pp.131-135
    • /
    • 2006
  • A seismic waveform inversion for prestack seismic data based on the Gauss-Newton method is presented. The Gauss-Newton method for seismic waveform inversion was proposed in the 80s but has rarely been studied. Extensive computational and memory requirements have been principal difficulties. To overcome this, we used different sizes of grids in the inversion stage from those of grids in the wave propagation simulation, temporal windowing of the simulation and approximation of virtual sources for calculating partial derivatives, and implemented this algorithm on parallel supercomputers. We show that the Gauss-Newton method has high resolving power and convergence rate, and demonstrate potential applications to real seismic data.

  • PDF

Application of ADE-PML Boundary Condition to SEM using Variational Formulation of Velocity-Stress 3D Wave Equation (속도-응력 변분식을 이용한 3차원 SEM 탄성파 수치 모사에 대한 ADE-PML경계조건의 적용)

  • Cho, Chang-Soo;Son, Min-Kyung
    • Geophysics and Geophysical Exploration
    • /
    • v.15 no.2
    • /
    • pp.57-65
    • /
    • 2012
  • Various numerical methods in simulation of seismic wave propagation have been developed. Recently an innovative numerical method called as the Spectral Element Method (SEM) has been developed and used in wave propagation in 3-D elastic media. The SEM that easily implements the free surface of topography combines the flexibility of a finite element method with the accuracy of a spectral method. It is generally used a weak formulation of the equation of motion which are solved on a mesh of hexahedral elements based on the Gauss-Lobatto-Legendre integration rule. Variational formulations of velocity-stress motion are newly modified in order to implement ADE-PML (Auxiliary Differential Equation of Perfectly Matched Layer) in wave propagation in 3-D elastic media, because a general weak formulation has a difficulty in adapting CFS (Complex Frequency Shifted) PML (Perfectly Matched Layer). SEM of Velocity-Stress motion having ADE-PML that is very efficient in absorbing waves reflected from finite boundary is verified with simulation of 1-D and 3-D wave propagation.

Prediction of Strong Ground Motion in Moderate-Seismicity Regions Using Deterministic Earthquake Scenarios

  • Kang, Tae-Seob
    • Journal of the Earthquake Engineering Society of Korea
    • /
    • v.11 no.4
    • /
    • pp.25-31
    • /
    • 2007
  • For areas such as the Korean Peninsula, which have moderate seismic activity but no available records of strong ground motion, synthetic seismograms can be used to evaluate ground motion without waiting for a strong earthquake. Such seismograms represent the estimated ground motions expected from a set of possible earthquake scenarios. Local site effects are especially important in assessing the seismic hazard and possible ground motion scenarios for a specific fault. The earthquake source and rupture dynamics can be described as a two-step process of rupture initiation and front propagation controlled by a frictional sliding mechanism. The seismic wavefield propagates through heterogeneous geological media and finally undergoes near-surface modulations such as amplification or deamplification. This is a complex system in which various scales of physical phenomena are integrated. A unified approach incorporates multi-scale problems of dynamic rupture, radiated wave propagation, and site effects into an all-in-one model using a three-dimensional, fourth-order, staggered-grid, finite-difference method. The method explains strong ground motions as products of complex systems that can be modified according to a variety of fine-scale rupture scenarios and friction models. A series of such deterministic earthquake scenarios can shed light on the kind of damage that would result and where it would be located.

Seismic microzonation of Kolkata

  • Shiuly, Amit;Sahu, R.B.;Mandal, Saroj
    • Geomechanics and Engineering
    • /
    • v.9 no.2
    • /
    • pp.125-144
    • /
    • 2015
  • This paper presents the probabilistic seismic microzonation of densely populated Kolkata city, situated on the world's largest delta island with very soft alluvial soil deposit. At first probabilistic seismic hazard analysis of Kolkata city was carried out at bedrock level and then ground motion amplification due to sedimentary deposit was computed using one dimensional (1D) wave propagation analysis SHAKE2000. Different maps like fundamental frequency, amplification at fundamental frequency, peak ground acceleration (PGA), peak ground velocity (PGV), peak ground displacement (PGD), maximum response spectral acceleration at different time period bands are developed for variety of end users, structural and geotechnical engineers, land use planners, emergency managers and awareness of general public. The probabilistically predicted PGA at bedrock level is 0.12 g for 50% exceedance in 50 years and maximum PGA at surface level it varies from 0.095 g to 0.18 g for same probability of exceedance. The scenario of simulated ground motion revealed that Kolkata city is very much prone to damage during earthquake.

Influence of ground motion spatial variations and local soil conditions on the seismic responses of buried segmented pipelines

  • Bi, Kaiming;Hao, Hong
    • Structural Engineering and Mechanics
    • /
    • v.44 no.5
    • /
    • pp.663-680
    • /
    • 2012
  • Previous major earthquakes revealed that most damage of the buried segmented pipelines occurs at the joints of the pipelines. It has been proven that the differential motions between the pipe segments are one of the primary reasons that results in the damage (Zerva et al. 1986, O'Roueke and Liu 1999). This paper studies the combined influences of ground motion spatial variations and local soil conditions on the seismic responses of buried segmented pipelines. The heterogeneous soil deposits surrounding the pipelines are assumed resting on an elastic half-space (base rock). The spatially varying base rock motions are modelled by the filtered Tajimi-Kanai power spectral density function and an empirical coherency loss function. Local site amplification effect is derived based on the one-dimensional wave propagation theory by assuming the base rock motions consist of out-of-plane SH wave or combined in-plane P and SV waves propagating into the site with an assumed incident angle. The differential axial and lateral displacements between the pipeline segments are stochastically formulated in the frequency domain. The influences of ground motion spatial variations, local soil conditions, wave incident angle and stiffness of the joint are investigated in detail. Numerical results show that ground motion spatial variations and local soil conditions can significantly influence the differential displacements between the pipeline segments.