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Near-Surface Seismic Methods To Enhance Reflection Events In High Desert Region
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 21st EEGS Symposium on the Application of Geophysics to Engineering and Environmental Problems, Apr 2008, cp-177-00061
Abstract
Statics are a concern on most seismic surveys and the key to addressing the statics problem is accurate estimations of near-surface velocity variability. Near-surface variabilities in weathered or sub-weathered layers can cause trace-to-trace time irregularities that adversely affect the ultimate quality and therefore useability of a CMP stacked section. In some dry, unconsolidated geologies velocity analysis can present a significant problem due to considerable overburden thickness with lateral variability and relatively shallow target depths (500-700 m). In this study we explore different methods to enhance NMO corrections by focusing on defining a detailed velocity model for the “weathered” interval. These methods attempt to increase reflection coherency by selecting a velocity function that possess realistic NMO and interval values using unfiltered data. Data for this study was acquired in the high desert of northern Nevada. Vibroseis data were recorded across a 15-150 Hz sweep range using a 240 channel recording system. Attention to variability in the velocity model both laterally and in depth, results in a superior image of the subsurface.