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COMPARISON OF METHODS TO DETERMINE Q IN SHALLOW MARINE SEDIMENTS FROM VERTICAL REFLECTION SEISMOGRAMS *
Author(s) -
JANNSEN D.,
VOSS J.,
THEILEN F.
Publication year - 1985
Publication title -
geophysical prospecting
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.735
H-Index - 79
eISSN - 1365-2478
pISSN - 0016-8025
DOI - 10.1111/j.1365-2478.1985.tb00762.x
Subject(s) - seismogram , geology , wavelet , reflection (computer programming) , computation , mineralogy , dispersion (optics) , optics , seismology , algorithm , physics , mathematics , computer science , artificial intelligence , programming language
A bstract Four methods for the determination of Q in marine sediments are compared: two traditional methods, i.e. the risetime and the spectral ratio method, and two newly established ones, the spectrum modeling and the wavelet modeling method. In the latter one Q and the reflection time T are determined simultaneously, which gives a much better accuracy for T than reading it from the seismogram. The risetime and the spectral ratio methods are used for obtaining Q directly from the data. The principle of the modeling methods is to calculate the effect of absorption and dispersion on a reference wavelet or its spectrum for various values of Q, and the best fit between the observed and the calculated data leads to the optimum result. Numerical tests on synthetic data show that a precision of more than 25% for data containing noise or superposed arrivals can hardly be achieved; in any case, wavelet modeling is the superior method. Application to data from a vertical reflection profile in the Baltic Sea yields Q in the range of 15–100 for different layers, which is to be expected in the sedimentary environment of this area. The computations were performed in the Computer Center of Kiel University. The authors thank R. Meissner for his comments on the manuscript.