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02h0020827 20101216110657.0 cr un||||||||| 101021s2000 xx ||||f|||d||||||||eng | 0612538389(ebk.) : CNY371.35 (UnM)AAINQ53838 UnM UnM NGL a380 ; a631 Nedimovic, Mladen R. Seismic reflection imaging in crystalline terrains [electronic resource] / Mladen R. Nedimovic. 2000. 185 p. : digital, PDF file. Source: Dissertation Abstracts International, Volume: 61-11, Section: B, page: 5768. ; Adviser: Gordon F. West. Thesis (Ph.D) -- University of Toronto (Canada), 2000. Seismic refection surveying is a well proven geophysical method for delineating in detail the deep structure of sedimentary basins. Recently, it has also been applied in igneous and metamorphic (crystalline) rock environments. For cost and access reasons most of the data collected in crystalline terrains has been acquired by 2D crooked line profiling. But where the survey geometry is significantly irregular and the geologic structures have cross-profile dip, standard 2D imaging procedures severely underperform.;My research has focused on finding remedies for the above problems by exploring and developing processing methods which usefully exploit the 3D character of crooked line data, or by finding methods of imaging that are more tolerant to the errors.;To these ends I have designed the following data manipulation processes: (1) 3D prestack migration of 2D crooked lane data. Despite obvious data limitations, bands of reflectivity recorded in crooked line data are preserved and positioned to their true subsurface locations. (2) Optimum cross dip analysis/stack. This algorithm first analyzes cross-profile dip of the imaged reflectors and then collapses recorded bands of reflectivity into single events. (3) Amplitude stack. This is a simple procedure used as a measure of last resort when 1 and 2 fail to yield 3D structural information.;From tests on synthetic data and two field data sets from the Archean Superior Province, I have found that: (1) When 2D crooked line geometry forms a 3D swath of data wider than a significant fraction of the Fresnel Zone radius at the depth of interest. 3D prestack migration will focus events in space well enough for interpretation. The process is, however, computationally cumbersome; (2) Although the cross dip stack does not output a 3D volume like prestack migration, and it retains only the stronger of overlapping reflective responses, it does provide most of the same interpretative information; (3) Amplitude stacks are surprisingly effective in imaging general structural trends.;In general, it is often possible to recover the 3D geometry of the structure imaged by a 2D crooked line survey. Seismic prospecting. ; Metamorphic rocks. ; Crystalline rocks. aWest, Gordon F. aCN bNGL http://proquest.calis.edu.cn/umi/detail_usmark.jsp?searchword=isbn%3D0612538389&singlesearch=no&channelid=%CF%B8%C0%C0&record=1 NGL Bs686 rCNY371.35 ; h1 xhbs1003
