Body and Surface Wave Modeling of Observed Seismic Events PDF Download

Author: Robert W. Clayton
Publisher:
ISBN:
Category :
Languages : en
Pages : 134

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Author: David G. Harkrider
Publisher:
ISBN:
Category : Earthquake simulators
Languages : en
Pages : 106

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Book Description
Contents: Time functions for nuclear explosions; A comparison of generalized ray and normal mode seismograms; Modeling earthquakes with generalized ray theory; Theoretical fault and block conversion of explosion P waves into SH and SV waves; Publications.

Author: Robert W. Clayton
Publisher:
ISBN:
Category :
Languages : en
Pages : 120

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Book Description
We first present a scheme for generating synthetic point source seismograms for shear dislocation sources using line source (2-D) theory. It is based on expanding the complete three dimensional solution of the wave equation expressed in cylindrical coordinates in an asymptotic form which provides for the separation of motions into SH and P-SV systems. We calculate the equations of motion with the aid of the Cagniard-deHoop technique and derive closed-form expressions appropriate for finite-difference source excitation. The effects of a thinning or thickening of the crustal layer on the propagation of Lg mode sum seismograms are also examined. The thinning or thickening of the crustal layer is used as a simple model of ocean to continent or continent to ocean transitions. The transition model calculations show that passage through a region of thinning crustal thickness (the model for a continent to ocean transition) increases the amplitude and coda length of the Lg wave at the surface, and allows much of the modal energy trapped in the crust, which forms the Lg phase, to escape into the subcrustal layers as body waves or other downgoing phases. The magnitude of both these effects increases as the length of the transition increases or the slope of the layer boundaries decrease.

Author: Robert W. Clayton
Publisher:
ISBN:
Category :
Languages : en
Pages : 162

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The main topics are: 1) the effects of lateral structure, in particular, complicated sedimentary basins on the propagation and amplication of seismic strong motion; and 2) the effects of ocean continent transition zones on L sub g waves. 1) 2-D finite difference techniques are used to model the seismic strong motions observed for the 1971 San Fernando earthquake. The finite difference seismograms show strong effects due to lateral variation in sediment thickness in the San Fernando valley and the Los Angeles basin. Using basin structure derived mostly from well logs and teleseismically determined source parameters, two dimensional SH and P-SV finite difference calculations reproduce the amplitude and duration of the strong motion velocities recorded across the Los Angeles and San Fernando basins for the period range 2-10 secs. The edges of basins nearest the seismic source show ground motion amplification up to a factor of three over the case without the basin, and tend to convert direct shear waves into Love and Rayleigh waves that travel within the basin. 2) The methods for Representation Theorem coupling of finite element or finite difference calculations and propagator matrix method calculations to produce a hybrid method for propagation of SH mode sum seismograms across paths that contain regions of non plane-layered structure are explained and developed.

Author: Robert W. Clayton
Publisher:
ISBN:
Category :
Languages : en
Pages : 142

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The research can be divided into two main topics; coupling line source calculations in 2-D lateral variations of near source structure to analytic teleseismic body wave codes, and the effects of ocean continent transition zones on L sub g waves. A new method is presented for interfacing numerical and integral techniques which allows greater flexibility in seismic modeling. Specifically, numerical calculations in laterally varying structure are interfaced with analytic methods that enable propagation to great distances. Such modeling is important in studying situations containing localized complex regions not easily handled by analytic means. The effects of the length of the intermediate path between the continent ocean and ocean continent transition regions is investigated. First the results of two FE calculations with different intermediate path lengths are presented and compared. These examples are contrasted with the path length used in the previous report. Then the RT integration method is discussed and explained. First analytic expressions for the stress components of double couple and line sources are derived, then the expressions for displacement and stress line source Green's functions are determined. These expressions are used to illustrate the validity and determine the accuracy of the RT coupling method.

Author: D. G. Harkrider
Publisher:
ISBN:
Category : Earthquake simulators
Languages : en
Pages : 113

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Contents: A Generalized Reflection - Transmission Coefficient Matrix and Discrete Wavenumber Method for Synthetic Seismograms; Body Wave Amplitude and Travel Time Correlations across North America; and Evidence of Tectonic Release from Underground Nuclear Explosions in Long-period P-waves.

Author:
Publisher:
ISBN:
Category : Military research
Languages : en
Pages : 452

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Author: Anatoli L. Levshin
Publisher: Springer Science & Business Media
ISBN: 9783764365516
Category : Science
Languages : en
Pages : 260

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Book Description
On September 1996, the United Nations General Assembly adopted the Comprehensive Nuclear-Test-Ban Treaty (CTBT), prohibiting nuclear explosions worldwide, in all environments. The treaty calls for a global verification system, including a network of 321 monitoring stations distributed around the globe, a data communications network, an international data center (IDC), and on-site inspections to verify compliance. Seismic methods play the lead role in monitoring the CTBT. This volume concentrates on the measurement and use of surface waves in monitoring the CTBT. Surface waves have three principal applications in CTBT monitoring: to help discriminate nuclear explosions from other sources of seismic energy, to provide mathematical characterizations of the seismic energy that emanates from seismic sources, and to be used as data in inversion for the seismic velocity structure of the crust and uppermost mantle for locating small seismic events regionally. The papers in this volume fall into two general categories: the development and/or application of methods to summarize information in surface waves, and the use of these summaries to advance the art of surface-wave identification, measurement, and source characterization. These papers cut across essentially all of the major applications of surface waves to monitoring the CTBT. This volume therefore provides a general introduction to the state of research in this area and should be useful as a guide for further exploration.

Author: Bruce Bolt
Publisher: Elsevier
ISBN: 0323155952
Category : Science
Languages : en
Pages : 321

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Book Description
Methods in Computational Physics, Volume 11: Seismology: Surface Waves and Earth Oscillations is a five-chapter text that deals with the computational analysis of surface waves and the eigenvibrations of the Earth. Chapter 1 describes the advances in the numerical modeling of geological structures where the appropriate partial differential equations with boundary conditions for heterogeneous materials are solved using an intricate finite difference scheme. Chapter 2 presents the computer techniques of processing seismograms to obtain information on the dispersion of seismic surface waves, while Chapter 3 explains the fast algorithms for computation of eigenvalues in surface wave and terrestrial eigenvibration problems. Chapter 4 presents a competing method, much used in structural engineering and soil mechanics. Chapter 5 is devoted to the propagation of surface waves in layered media, which indicate that density and elasticity vary only in the vertical direction. This chapter also provides the fundamentals and numerical aspects of the theory of seismic surface waves. This book is an invaluable source for seismologists, earthquake engineers, and graduate students.

Author:
Publisher:
ISBN:
Category : Aeronautics
Languages : en
Pages : 880

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Book Description
Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.