Dependence of theP-wave amplitude spectrum on focal depth
- 32 Downloads
Four spectral parameters, each of which reflects a certain spectral characteristic, are computed for 67 power spectra of earthquakes. The analyzed signals used in this work are theP-phases recorded by short-period, vertical-component seismographs.
In correlating the values of the spectral parameters with the respective focal depths, a qualitative ‘spectrum-depth’ relation is obtained. The most outstanding feature of the relationship thus computed, is a pronounced anomaly in the depth-range of 50–250 km. This is found to correlate rather well with the location of the low-velocity layer which many seismologists have shown to exist in the earth's upper mantle. With the aid of results obtained from experimental work on rock blasts, it is argued that the anomalous zone has more viscous character than the overlying and underlying media.
KeywordsPower Spectrum Experimental Work Spectral Characteristic Analyze Signal Spectral Parameter
Unable to display preview. Download preview PDF.
- T. Asada andK. Takano,Attenuation of short period P-waves in the mantle, J. Phys. Earth11 (1963), 25.Google Scholar
- M. Båth,Some consequences of the existence of low-velocity layers, Ann. Geofis.9 (1956), 441.Google Scholar
- M. Båth,Lateral inhomogeneities of the upper mantle, Tectonophysics,2 (1965), 483.Google Scholar
- J. Dorman, M. Ewing andJ. Oliver,Study of shear-velocity distribution in the upper mantle by mantle Rayleigh waves, Bull. Seism. Soc. Am.50 (1960), 87.Google Scholar
- M. A. Enayatollah,Travel times of P-waves for the Swedish-Finnish seismograph network, Pure and Appl. Geophys.94 (1972), 101.Google Scholar
- M. A. Enayatollah,Continental-array measurements of P-wave velocities in the mantle, Pure and Appl. Geophys.94 (1972), 136.Google Scholar
- B. Gutenberg,Attenuation of seismic waves in the earth's mantle, Bull. Seism. Soc. Am.48 (1958), 269.Google Scholar
- N. V. Kondorskaya, L. N. Pavlov, A. N. Pustovitenko andS. L. Solov'ev,Some results of a study of the longitudinal-wave spectra from earthquakes in the Far East, Izv. Acad. Sci. USSR, Phys. Solid Earth No. 1 (1967), 36 (Engl. ed.).Google Scholar
- B. Mohammadioun,Structure du manteau supérieur et spectres d'énergie des ondes longitudinales, C.R. Acad. Sc. Paris.,261 (1965), 4472.Google Scholar
- E. A. Robinson,Multichannel Time Series Analysis with Digital Computer Programs (Holden-Day, Inc., San Francisco, 1967).Google Scholar
- S. L. Solov'ev andA. N. Pustovitenko,On the possible reduction in period of longitudinal waves as the depth of the earthquake focus increases, Izv. Acad. Sci. USSR, Geophys. Ser., No. 6 (1964), 508 (Engl. ed.)Google Scholar
- M. Tsujiura,Frequency analysis of seismic waves (1), Bull. Earthq. Res. Inst. (Tokyo)44 (1966), 873.Google Scholar
- M. Tsujiura,Frequency analysis of seismic waves (2), Bull. Earthq. Res. Inst. (Tokyo)45 (1967), 973.Google Scholar
- M. Tsujiura,Regional variation of P-wave spectrum (1), Bull. Earthq. Res. Inst. (Tokyo)47 (1969), 613.Google Scholar