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Attenuation estimation in thin transitional layers with gradational velocity change
Author(s) -
Tian Gang,
Cheng Suo,
Shi Zhanjie,
Wang Kai
Publication year - 2008
Publication title -
near surface geophysics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.639
H-Index - 39
eISSN - 1873-0604
pISSN - 1569-4445
DOI - 10.3997/1873-0604.2007039
Subject(s) - stratum , seismogram , geology , attenuation , reflection (computer programming) , anelastic attenuation factor , amplitude , filter (signal processing) , seismology , economic geology , seismic wave , love wave , geophysics , wave propagation , mineralogy , optics , geotechnical engineering , longitudinal wave , mechanical wave , physics , tectonics , metamorphic petrology , computer science , computer vision , programming language
In a desert area, unconsolidated sediment can seriously attenuate the high frequency components of seismic data. In order to evaluate the attenuation of a seismic wave in the medium, we firstly analysed the primary seismic wave from up‐hole survey data acquired from the Takelamagan desert of north‐west China and then performed numerical simulations. The up‐hole results showed that there is a stratum in which the velocity increases gradually when the depth increases and where amplitudes and frequency components are attenuated and are decreased seriously by the waves being reflected or passing through the stratum. We regard the stratum as a linear transition layer. Based on the linear transition theory and the velocity structures obtained from up‐hole data, the one‐dimensional numerical simulation method was used to calculate seismograms of transmission waves and reflection waves. By analysing these two records, it was found that both amplitudes and frequency components attenuated greatly due to the existing linear transition layer. This can be interpreted as scattering or multiples since the reflection and the transmission actions usually occurred in this kind of stratum more than once. This is a significant factor for the amplitudes and frequency components attenuation of a partially saturated layer in a desert area. The filter character of the transition stratum can be described as a low‐pass filter for reflection waves and as a high‐pass filter for transmission waves.