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Index Geophysics

Amplitude study of the Pg phase


Title (Dublin Core)

en-US Amplitude study of the Pg phase

Description (Dublin Core)

en-US The amplitude of the Pg phase, as recorded in explosion seismology studies, is analyzed with the aid of synthetic seismograms. Parameters such as source frequency, low-velocity cover above the crust (sediments or weathered layer), low-velocity layers within the upper crust, velocity gradients, thickness of the gradient zone, attenuation and Poisson's ratio strongly influence the amplitude-distance pattern of the Pg phase. A systematic study clearly shows that different models of the continental upper crust display distinct amplitude-distance characteristics. These models could not be distinguished by travel-time interpretation alone. In the presence of gradient zones the amplitude-distance curve shows different patterns depending on the source frequency. The higher the frequency, the more pronounced are the relative maxima in the amplitudes. The presence of a low-velocity cover at the surface accentuates the character of the amplitude-distance curves even if the cover is thin (a few hundred meters). Moreover, a low-velocity cover produces P to S conversions and multiples following the Pg which obscure possible secondary crustal phases. The thickness of the velocity gradient zone influences the amplitude decay and the width of the relative maxima. Low-velocity layers within the upper crust cause a faster drop-off of the amplitudes than would be expected from ray theory. Detailed Pg amplitude studies are thus useful in improving the knowledge of the physical properties of the upper continental crust. The application of the derived criteria to two sets of real data allow us to determine fine details of the velocity-depth function which are of great importance for the understanding of the Earth's crust.

Creator (Dublin Core)

Banda, E.
Deichmann, N.
Braile, L.W.
Ansorge, J.

Subject (Dublin Core)

en-US Explosion seismology
en-US Upper continental crust
en-US Seismic amplitude
en-US Source frequency
en-US Low-velocity layer
en-US Velocity gradient
en-US Seismology

Publisher (Dublin Core)

en-US Journal of Geophysics

Date (Dublin Core)


Type (Dublin Core)

en-US Peer-reviewed Article

Format (Dublin Core)


Identifier (Dublin Core)

Source (Dublin Core)

en-US Journal of Geophysics; Vol 51 No 1 (1982): Journal of Geophysics; 153-164

Language (Dublin Core)


Relation (Dublin Core)