HR: 10:30h
AN: S52A-01    [Abstracts]
TI: Sub-Basalt Imaging Using Long-Offset Seismic Data
AU: * Goloshubin, G
EM: ggoloshubin@uh.edu
AF: University of Houston, 504 Science and Research Bldg 1, Houston, TX 77204-5006 United States
AB: Basalt layers usually have a complex structure with thin layers and large velocity and density differences. They may be inhomogeneous in all directions and may display a positive velocity gradient. Such complex structures create quasi-anisotropy, high- frequency scattering, low-frequency absorption, and refraction. In general, it is not difficult to map the top of a basalt layer because it is a strong reflector. But multiples from the sea bottom and top of the basalt generally mask sub-basalt reflected waves. Multiple attenuation methods do not always provide the low-level of remnants of multiples in case of near-offset data. Sub-basalt reflected and refracted waves at far-offsets are free from the problems of multiples. In addition, reflected waves at far-offsets have high amplitudes because the reflection coefficient of the waves approaches unity, and the strong influence of basalt inhomogeneity is reduced. The long-offset (0-16 km) seismic data were used for sub-basalt imaging at 3-5 km depth. A three step methodology was utilized to construct the image of sub-basalt sediments: 1) getting of the image and velocity model of the low-velocity sediments above basalt (including its top) by processing of the reflected waves at near-offset (0-6 km); 2) construction of the basalt layer model by reflected waves observed at far-offset (6-16 km) with high apparent velocity (about 5 km/s); 3) recognition of the sub-basalt sediments and construction of the sub-basalt seismic image based on first two steps. Besides methodology the results of the sub-basalt imaging using long-offset data are discussed.
DE: 8000 STRUCTURAL GEOLOGY (New field, replaces single entry 8165)
DE: 8180 Tomography
SC: Seismology [S]
MN: 2005 Joint Assembly