Seismic Wave Attenuation In Eastern North America
DOWNLOAD
Download Seismic Wave Attenuation In Eastern North America PDF/ePub or read online books in Mobi eBooks. Click Download or Read Online button to get Seismic Wave Attenuation In Eastern North America book now. This website allows unlimited access to, at the time of writing, more than 1.5 million titles, including hundreds of thousands of titles in various foreign languages. If the content not found or just blank you must refresh this page
Seismic Wave Attenuation In Eastern North America
DOWNLOAD
Author : I. N. Gupta
language : en
Publisher:
Release Date : 1989
Seismic Wave Attenuation In Eastern North America written by I. N. Gupta and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with Earth movements categories.
Seismic Wave Attenuation In Eastern North America Project 2556 9
DOWNLOAD
Author : Geotech Teledyne
language : en
Publisher:
Release Date : 1989
Seismic Wave Attenuation In Eastern North America Project 2556 9 written by Geotech Teledyne and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1989 with categories.
Seismic Wave Attenuation
DOWNLOAD
Author : M. N. Toksöz
language : en
Publisher:
Release Date : 1981
Seismic Wave Attenuation written by M. N. Toksöz and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1981 with Geophysics categories.
"We have undertaken the editing of this volume to help the broad-range research effort gain a better understanding of attenuation and its applications to seismic exploration problems... We have emphasized the material most relevant to exploration geophysics. As a result, most of the papers compiled here deal with sedimentary rocks, the effects of fluids, and the pressure ranges encountered in shalow crustal layers."--Preface.
Ground Motion Attenuation And Earthquake Source Scaling In Eastern North America
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 1992
Ground Motion Attenuation And Earthquake Source Scaling In Eastern North America written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with Earth movements categories.
An Investigation Of Seismic Wave Propagation In The Eastern United States
DOWNLOAD
Author : David E. Willis
language : en
Publisher:
Release Date : 1968
An Investigation Of Seismic Wave Propagation In The Eastern United States written by David E. Willis and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1968 with Seismic waves categories.
The paper describes the travel-time anomalies and attenuation losses of seismic compressional waves generated by a series of underwater explosions in the eastern United States. The efficient tamping of the shots fired in water provided a seismic source that could be detected at much larger ranges than could be accomplished by equivalent sized shots fired underground. A number of mobile field recording stations equipped with three-component matched short period seismometers and magnetic tape recorders were used to record 273 individual shots. A total of 1,295 recordings were obtained along a reversed profile extending from International Falls, Minnesota to the Atlantic Coast. The underwater shots were fired in Lake Superior and the Atlantic Ocean. Precise travel times were obtained by recording radio time signals at all of the recording stations. An analysis of the travel-times of the seismic waves disclosed that the earth's crust varies in thickness from 28.1 km near the Atlantic Coast in North Carolina to 50.4 km near the Keweenaw Peninsula in upper Michigan. The crust in North Carolina was found to be comprised of a single layer with a compressional wave velocity of 6.0 km/sec. A two-layer crust with compressional wave velocities of 6.2 and 7.7 km/sec was disclosed in upper Michigan. Travel time residuals across the Appalachian Mts. would indicate a mountain root system similar to that found under the Rocky Mts. The Lake Superior area was found to be more efficient in the coupling of energy into seismic waves by the underwater shots than in the Atlantic Ocean. (Author).
An Investigation Of Seismic Wave Propagation In Eastern North America
DOWNLOAD
Author : P. W. Pomeroy
language : en
Publisher:
Release Date : 1978
An Investigation Of Seismic Wave Propagation In Eastern North America written by P. W. Pomeroy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1978 with categories.
Seismic waves propagated and recorded at regional distances in eastern North America are being studies for possible use in discriminating between explosion and earthquake sources. This report deals with (a) the propagation characteristics of the regional seismic wave designated L sub g and (b) an evaluation of the usefulness of a particular ocean bottom seismograph system as an aid in discrimination of seismic sources at regional distances. Results of the study of the propagation characteristics of L sub g, with predominant frequencies of 1-3 hertz, is consistently the largest amplitude portion of the short period signal from the Eastern North American events studied. Analysis of the group velocity for each event studied shows a clustering of measurements in the 3.47 km/sec range for the earthquakes studied and a significantly lower 3.24 km/sec mean for measurements from the SALMON explosion. This lower value is believed to be the result of propagation path or source effects. When group velocity information was divided into two regions, E (h)--high group velocity (4.0-3.4 km/sec) energy--and E(l)--low group velocity (3.4-2.8 km/sec) energy, the ratios of these areas showed a discrimination between SALMON ((E(h)/E(l) .5) and the earthquakes ((E(h)/E(l).5). Phase velocity measurements made using records from Cumberland Plateau Seismic Observatory have a mean of 4.18 km/sec. Analysis of a second event also yields measurements in the 4.0-4.4 km/sec range.
Seismic Wave Propagation And Scattering In The Heterogenous Earth
DOWNLOAD
Author : Haruo Sato
language : en
Publisher: Springer Science & Business Media
Release Date : 2008-12-17
Seismic Wave Propagation And Scattering In The Heterogenous Earth written by Haruo Sato and has been published by Springer Science & Business Media this book supported file pdf, txt, epub, kindle and other format this book has been release on 2008-12-17 with Science categories.
Seismic waves – generated both by natural earthquakes and by man-made sources – have produced an enormous amount of information about the Earth's interior. In classical seismology, the Earth is modeled as a sequence of uniform horizontal layers (or sperical shells) having different elastic properties and one determines these properties from travel times and dispersion of seismic waves. The Earth, however, is not made of horizontally uniform layers, and classic seismic methods can take large-scale inhomogeneities into account. Smaller-scale irregularities, on the other hand, require other methods. Observations of continuous wave trains that follow classic direct S waves, known as coda waves, have shown that there are heterogeneities of random size scattered randomly throughout the layers of the classic seismic model. This book focuses on recent developments in the area of seismic wave propagation and scattering through the randomly heterogeneous structure of the Earth, with emphasis on the lithosphere. The presentation combines information from many sources to present a coherent introduction to the theory of scattering in acoustic and elastic materials and includes analyses of observations using the theoretical methods developed.
Seismic Attenuation Studies In The Middle East And Southern Asia
DOWNLOAD
Author :
language : en
Publisher:
Release Date : 1996
Seismic Attenuation Studies In The Middle East And Southern Asia written by and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1996 with categories.
Previous research has indicated that the Middle East and southern Asia are characterized by high attenuation that may be caused by high intrinsic absorption, scattering by complex velocity structure, or both. We are trying to model these attenuative properties by measuring the attenuation of Lg coda waves as well as fundamental-mode surface waves in that region. Determinations of Lg coda Q there have allowed us to complete our map of Lg coda Q for all of Eurasia. Initial determinations of fundamental-mode Rayleigh and Love wave attenuation, using a two-station method indicate that attenuation for those waves, especially at short periods, is very high. This suggests that Q in the upper crust is very low, a result that is consistent with our Lg coda Q results. A new code has been developed for measuring dispersion and polarization properties of surface waves. Initial tests with code indicate that surface wave propagation in the Middle East is often complex and marked by lateral refraction and mode conversion along the paths of propagation.
The Seismic Attenuation Structure Of The East Pacific Rise
DOWNLOAD
Author : William Sam Douglas Wilcock
language : en
Publisher:
Release Date : 1992
The Seismic Attenuation Structure Of The East Pacific Rise written by William Sam Douglas Wilcock and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1992 with East Pacific Rise categories.
Studies of seismic propagation through oceanic crust have contributed enormously to our understanding of the generation and evolution of oceanic crust However, such work has largely been confined to the seismic velocity structure. In this thesis we present results from a study of seismic attenuation using a data set collected for three-dimensional tomographic imaging of a fast-spreading ridge. The experiment location at 9°30'N on the East Pacific Rise is the site of a strong mid-crustal seismic reflector which has been inferred to be the roof of a small axial magma chamber at about 1.6 km depth. A spectral method is used to estimate t*, a measure of the integrated attenuation along a wave path. Such a method asswnes that the dominant frequency-dependent component of propagation is intrinsic attenuation. A logarithmic parameterization is then used to invert t* measurements for Q-1 structure asswning that the velocity structure is given from earlier studies. To evaluate the method of Q tomography a full-waveform finitedifference technique which does not include attenuation is used to calculate solutions for seismic propagation through a two-dimensional velocity model. The results show a complex pattern of seismic propagation in the vicinity of the axial magma chamber. The first arrival always passes above the magma chamber. However, for paths of significant length that cross the rise axis the amplitude of this arrival is very small, and the first phase with significant amplitude is a diffraction below the magma chamber. High-amplitude Moho turning and PP arrivals may also be important secondary arrivals. Synthetic inversions show the importance of selecting time windows for power spectral estimation which are dominated by a single phase and of using wave paths which closely corresponds to that of the selected phase. A comparison of the finite difference solutions and the predictions of the a twodimensional, exact ray-tracing algorithm with record sections obtained during the tomography experiment significantly improves our understanding of seismic propagation across the East Pacific Rise. The results enable an objective choice of the position and length of the time window fort* estimation. Moreover, additional constraints are incorporated into an approximate three-dimensional ray-tracing algorithm used in the inversion so that the wave paths more closely correspond to those of the desired phase. The full data set to be inverted comprises about 3500 t* estimates and includes crustal paths which do not cross the rise axis, diffractions above and below the axial magma chamber, and Moho-turning phases. Wave paths for the Moho-turning phases cross the rise axis at a wide range of lower crustal depths. The Q-1 models resulting from two-dimensional and three-dimensional tomographic inversions show that the attenuation of seismic waves on the East Pacific Rise is dominated by two regions of low Q; one in the upper 1 km of crust, and one at depths greater than about 2 km below the rise axis. While the data do not resolve the details of vertical variations in near-surface Q-1, the results show a substantial variation in shallow attenuation within 0.05 My of the rise axis. On-axis, Q values averaged over the upper 1 km are about 100, while off-axis the average value rapidly decreases to about 30. Measurements of the seismic velocity suggest that the thickness of the surficial highporosity extrusive layer increases substantially off-axis. If such thickening is entirely responsible for the observed change in near-surface attenuation then Q within the extrusive layer must be much less than 20. Alternatively, in situ changes in porosity may also contribute to the observed increase in attenuation. Since significant tectonic activity is apparently restricted to locations well off-axis we suggest that such variations in porosity may result from hydrothermal activity. Regions of hydrothermal downwelling located off-axis will be subject to cooling and thermally-induced cracking while upwelling regions on-axis may be accompanied by rapid infilling of existing pores by hydrothermal deposits. Estimates of t* for all phases propagating below the magma chamber are markedly higher than those for other phases, resulting in Q-1 models which include a region of low Q extending from 2 to 7 km depth below the rise axis. The lowest Q values resolved are about 25-30 both immediately below the magma chamber and within the lower crust. While there is some evidence for a small decrease in attenuation with depth in the lower crust, axial Q values at depths ranging from less than 2.5 to 6 km are relatively constant, always lying below 50. Laboratory measurements at seismic frequencies suggest that Q values of 25-50 require only very small fractions of partial melt. The attenuation observations thus place constraints on the dimensions of the axial magma chamber and strongly suggest that the thickness of the region containing more than a few percent of partial melt is no more than 1 km.
A Comparison Of Teleseismic P Wave Amplitudes And Spectra Observed At Selected Basin And Range Sites And In Eastern North America Phase 1
DOWNLOAD
Author : Z. A. Der
language : en
Publisher:
Release Date : 1978
A Comparison Of Teleseismic P Wave Amplitudes And Spectra Observed At Selected Basin And Range Sites And In Eastern North America Phase 1 written by Z. A. Der and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1978 with categories.
Three Seismic Data Collection System (SDCS) stations were deployed at the Nevada Test Site (NTS) and two in the Eastern United States (EUS) to measure magnitude residuals and spectral differences between NTS and EUS stations. The deployment was intended to determine the degree of anelastic attenuation under NTS. At the Climax Stock (OB2NV) station, the teleseismic body-wave magnitudes are .17 magnitude units (m.u.) lower than at the EUS stations. The magnitudes at the two Pahute Mesa sites are about .2 m.u. higher than at OB2NV, a difference that can be accounted for by amplification of low velocity volcanics under Pahute Mesa. Thus local geology must be taken into account in order to evaluate the attenuation under a given site using amplitude data. This correction shows that with respect to corrected amplitude levels OB2NV is equivalent to Pahute Mesa stations. At all NTS sites the higher frequency content of P waves is significantly less than in the EUS. Available data suggests an attenuation effect of about .2 m.u. under NTS. Measurements at a few other Western United States (WUS) sites, including the site of the SHOAL explosion, yield similar figures. These results confirm that body-waves suffer considerable anelastic losses traversing the mantle under the WUS, including the NTS sites. (Author).