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Quantitative zerst
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A scheme recently proposed by the authors for constructing Earth models which fit a given finite set of gross Earth data is applied to the problem of constructing a P-velocity structure which, within experimental error, fits the observed travel times in the range Δ = 25°(5°)95°. Three such models are obtained, all of which fit the observed travel times with residuals less than 0.06s, whereas 0.5s is the estimated standard error of the observations. The models differ mainly in the outer 700 km of the mantle.
Describes how seismological progress has led to the contemporary understanding of earthquake origins, and discusses in detail the major contributions to modern theory. There is an initial compilation of quantitative views of earthquake origins and the main part considers the fault-origin model of earthquakes, with detailed examinations of basic concepts (with examples). This is followed by a discussion of physical, rockmechanical and tectonic problems of earthquake occurrence. The final chapter explains how the previous subjects discussed can be brought together to explore the problems of earthquake prediction and control. The text is considered suitable for university students in seismology and solid-earth sciences, and for engineers and construction workers. -from Publisher
In order to evaluate defects in AE-testing there are three basic problems:
Firstly, we have to know relationships between the signal parameters from the AE-sources of different fracture mechanical processes. In the area of NDT the most important are plastic deformation and crack propagation. In some applications also friction noises from cracks are of interest. In general, these relationships are dependent upon the material and have to be found out in laboratory by test specimens. The results of such measurements show that the physical signal parameters, peak amplitude, energy, signal duration (related to a fixed distance from the peak amplitude), amplitude spectrum, are important in view of an interpretation of AE sources /1,2/.
In this paper some of the authors' recent research into acoustic emission (AE) is described. In searching for the source mechanisms of AE, the aim of waveform analysis may be to separate the effects of the propagation media and the transducers from the detected AE waveforms, and the determine the kinetic and kinematic characteristics of sources. Therefore, deconvolution techniques in both the time domain and the frequency domain are developed. They have been applied to investigate two basic types of sources, namely, a point force and a tensile crack. Results show that the authors' original notions concerning the source mechanisms of AE, which can be mathematically described by the dislocation model, are acceptable. The applicability of elastodynamics and the dislocation theory for studying the relation between the source mechanisms and wave motions of AE is also verified.
Handmade particleboard, representing a wide range of density and resin levels, was tested for internal bond (IB) while monitored for acoustic emission (AE) events. The 175-kHz AE sensor was mounted directly to the loading block attached to the specimen. Previous work has established a clear relationship between nominal AE events and IB for production industrial board, which was reaffirmed for the handmade boards. In addition, the total events to failure correlated to resin level, implying proportionality of events to number of bonds failing. A semilogarithmic relationship of events to load correlated well with IB, particularly at higher failure levels. Boards with IB above 800 kPa appeared to have a bimodal peak amplitude distribution, indicating wood as well as resin failure.