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Seismic attributes analysis is applied to INDEPTH II seismic profiles to develop a better understanding of the deep crustal structure and geodynamics of the Lhasa Terrane in the central Tibet area. Analyses indicate that the frequency anomalies are obtained over the range in between 0-30 Hz. Some area of the analyzed traces of the seismic profiles have shown dominated frequency anomaly approximately 10 Hz with little amount of other frequencies. The variation of frequency anomaly is shown to be the indication of theMoho depth of the area. EstimatedMoho depths are found very irregular and varying from20 kmto more than 136 km. The crust is thinner in southern, northern and eastern parts of the area while it is thicker in the western part having asymmetric nature in the central part. This variation might be the result of the complicated tectonic process of the Indian and Eurasian plates. Vertically downward pocket like frequency distributions and similar type frequency distributions at near and far depth are also observed in one of the analyzed sections. It might be indication of uprised asthenospheric matter which exchanged with lithosphere in subduction zones related to the multiple crustal uprising.

Group velocity dispersion has been computed for Chittagong earthquake of magnitude 5.6 that occurred on July 26, 2003 at 23:18:17 UTC, by graphical method. A model, taking subsurface layer parameters, is also constructed to compute the group velocity dispersion by modified Haskell matrix method. Group velocity dispersion by graphical method is then interpreted from model parameters. Sensitivity and the statistical errors of the model are studied and presented in this research. Interpreted crustal structure of the Chittagong area showed that there are four major subsurface layers of thickness 1.5 km, 5.0 km, 6.0 km and 8.0 km. [ABSTRACT FROM AUTHOR]

The abundance of mafic as well as ultramafic rocks of the oceanic crust was estimated through seismic attribute analysis. The analyses of the seismic profiles were assessed for compatible seismic images. Geological constituents of the oceanic crust were then sought to be interpreted from the images. Thin inter-layered depositional overview and crustal geology of the ocean were obtained from the amplitude and frequency attributes images. The geologic constituents were identified in frequency attribute images with the variation of frequency 0-60 Hz. The estimated geological constituents of the mid-Atlantic oceanic crust are: gabbro, peridotite, dunite and less than 1% serpentine content, according to frequency anomalies observed in the frequency attribute images. [ABSTRACT FROM AUTHOR]

Frequency contents of a seismic trace, varying with time carry information about the properties of the subsurface reflectivity sequence. In this paper, frequency transition technique for the reflection sequence analysis of the seismic data has been presented. The technique is the extension of the frequency attributes representation of seismic data. Frequency attributes, separate display of the seismic time amplitude maps, are computed with complex trace analysis. Moderate and sharp frequency variations are found all over the traces with time. Sharp frequency variations and the time of appearance are termed as transition frequency and transition time respectively. Transition-factor (T-factor) has delineated for marking the sharp frequency variation in the time frequency plots. T-factor differentiates high, moderate and transition frequency variations. The technique is explained with examples and has been applied for studying the reflection sequences of the INDEPTH seismic data. The proposed seismic reflection analysis can be used to identify the strata by sequence stratifying the seismic data. [ABSTRACT FROM AUTHOR]