Shallow 3D seismic-reflection imaging

journal_title：Geophysics
Contributor：Cedric Schmelzbach ; Heinrich Horstmeyer ; Christopher Juhlin
Publisher：Society of Exploration Geophysicists
Date：2007-
Format：text/html
Language：en
Identifier：10.1190/1.2787336
journal_abbrev：Geophysics
issn：0016-8033
volume：72
issue：6
firstpage：B149
section：CASE HISTORIES

摘要

A limited 3D seismic-reflection data set was used to map fracture zones in crystalline rock for a nuclear waste disposal site study. Seismic-reflection data simultaneously recorded along two roughly perpendicular profiles (1850 and $\text{[math]}$ long) and with a $\text{[math]}$ receiver array centered at the intersection of the lines sampled a $\text{[math]}$ area in three dimensions. High levels of source-generated noise required a processing sequence involving surface-consistent deconvolution, which effectively increased the strength of reflected signals, and a linear $\text{[math]}$ filtering scheme to suppress any remaining direct $\text{[math]}$ -wave energy. A flexible-binning scheme significantly balanced and increased the CMP fold, but the offset and azimuth distributions remain irregular; a wide azimuth range and offsets $\text{[math]}$ are concentrated in the center of the survey area although long offsets $\text{[math]}$ are only found at the edges of the site. Three-dimensional dip moveout and 3D poststack migration were necessary to image events with conflicting dips up to about 40°. Despite the irregular acquisition geometry and the high level of source-generated noise, we obtained images rich in structural detail. Seven continuous to semicontinuous reflection events were traced through the final data volume to a maximum depth of around $\text{[math]}$ . Previous 2D seismic-reflection studies and borehole data indicate that fracture zones are the most likely cause of the reflections.