Three‐dimensional (3-D) seismic reflection surveys have been the subject of much recent interest. However, use of the seismic refraction technique (Musgrave, 1967) in 3-D analyses should also be of considerable utility even though homogeneous layers separated by planar interfaces (not necessarily parallel or horizontal) must be assumed in most applications. A particular advantage of the refraction method is the straightforward determination of velocities.
Abstract : Seismic modeling techniques for one- and two-dimensional velocity models have been developed, tested and applied to analysis of observed seismic refraction and reflection data for the continental crust. The relfectivity method for one-dimensional models has proven to be an efficient and powerful method for interpretation of the amplitude and waveform of seismic record sections. The amplitude and waveform characteristics are shown to be important to interpretation of fine structure of velocity depth profiles. Applications to modeling of a variety of seismic phases are given. Two-dimensional modeling techniques utilizing ray-trace travel-time calculations and finite-difference synthetic seismogram calculations were developed. The ray-tracing methods are capable of accurate travel-time applications but require modification for amplitude analysis. The finite-difference method is a powerful technique capable of modeling seismic data for complex geologic structures for body and surface waves. Model studies for simple one- and two-dimensional velocity structures illustrate seismic wave propagation including complex amplitude and waveform characteristics due to model complexity. The principal limitation of the finite-difference technique is the large amount of computer time and storage required.
Reply| April 01, 1990 Reply to J. Vidale's “Comment on ‘A comparison of finite-difference and fourier method calculations of synthetic seismograms’” C. R. Daudt; C. R. Daudt Department of Earth and Atmospheric Sciences Purdue UniversityWest Lafayette, Indiana 47907 Search for other works by this author on: GSW Google Scholar L. W. Braile; L. W. Braile Department of Earth and Atmospheric Sciences Purdue UniversityWest Lafayette, Indiana 47907 Search for other works by this author on: GSW Google Scholar R. L. Nowack; R. L. Nowack Department of Earth and Atmospheric Sciences Purdue UniversityWest Lafayette, Indiana 47907 Search for other works by this author on: GSW Google Scholar C. S. Chiang C. S. Chiang Department of Earth and Atmospheric Sciences Purdue UniversityWest Lafayette, Indiana 47907 Search for other works by this author on: GSW Google Scholar Bulletin of the Seismological Society of America (1990) 80 (2): 496–497. https://doi.org/10.1785/BSSA0800020496 Article history received: 19 Oct 1989 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation C. R. Daudt, L. W. Braile, R. L. Nowack, C. S. Chiang; Reply to J. Vidale's “Comment on ‘A comparison of finite-difference and fourier method calculations of synthetic seismograms’”. Bulletin of the Seismological Society of America 1990;; 80 (2): 496–497. doi: https://doi.org/10.1785/BSSA0800020496 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyBulletin of the Seismological Society of America Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.
An integrated geophysical/geologic program is being conducted to evaluate the rift complex hypothesis as an explanation for the earthquake activity in the New Madrid Seismic Zone and its extensions, to refine our knowledge of the rift complex, and to investigate the possible northern extensions of the New Madrid Fault Zone, especially its possible connection to the Anna, Ohio seismogenic region. Drillhole basement lithologies are being investigated to aid in tectonic analysis and geophysical interpretation, particularly in the Anna, Ohio area. Gravity and magnetic modeling combined with limited seismic reflection studies in southwest Indiana are interpreted as confirming speculation that an arm of the New Madrid Rift Complex extends northeasterly into Indiana. The geologic and geophysical evidence confirm that the basement lithology in the Anna, Ohio area is highly variable reflecting a complex geologic history. The data indicate that as many as three major Late Precambrian tectonic features intersect within the basement of the Anna area suggesting that the seismicity may be related to basement zones of weakness.
This report, which includes a series of maps, is a compendium of the available information on several topics of importance in defining the geologic setting of crystalline rocks in the Lake Superior region (Minnesota, Wisconsin, and the Upper Peninsula of Michigan). Crystalline rocks are defined herein as bodies of medium; and coarse-grained igneous and high-grade metamorphic rocks. The study was undertaken to provide background information to assist in evaluating the suitability of such rocks for isolating high-level radioactive waste. Topics covered include geologic history of the region; patterns of earthquake occurrence, earthquake magnitudes and horizontal ground accelerations, crustal stress, regional fault domains, and Holocene faulting and vertical crustal movements; surface processes, anticipated climatic changes, and effects of renewed glaciation; landforms and surficial deposits; regional surface; and ground-water hydrology; and commercial potential of rock and mineral prospects of mines located within or near crystalline rock bodies. References, 117 figures, 36 tables.
Short-period (4 to 22 sec) Rayleigh waves generated by nuclear blasts at NTS and Rio Blanco were analyzed digitally to obtain group-velocity dispersion curves. These data were used to determine upper crustal structure for the eastern Basin and Range, northern Colorado Plateau, and Middle Rocky Mountains provinces. The crustal models obtained were in good agreement with refraction results. In the eastern Basin and Range, generally low S -wave velocities and an upper crustal low-velocity layer (LVL) were indicated, but there was no evidence for a LVL in the other provinces.
The cleaning and magnetic tape storage of spherical Earth processing programs are reported. These programs include: NVERTSM which inverts total or vector magnetic anomaly data on a distribution of point dipoles in spherical coordinates; SMFLD which utilizes output from NVERTSM to compute total or vector magnetic anomaly fields for a distribution of point dipoles in spherical coordinates; NVERTG; and GFLD. Abstracts are presented for papers dealing with the mapping and modeling of magnetic and gravity anomalies, and with the verification of crustal components in satellite data.
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