Wpływ stromych kontaktów warstw na realność obrazów sejsmicznych
Abstract
INFLUENCE OF STEEP CONTACTS OF BEDS UPON THE REALITY OF SEISMICAL PICTURES
Summary
Negligence of great changes Ln distribution of seismical mean velocities may lead to wrong interpretation of geological structure. In this connection a real example has been discussed of mean velocities in cross sections of SW-NE direction, through the deep bore holes Jaksmanice and Kańczuga, near Przemyśl, in which velocity loggings were made. The zone of changings is 4-6 km wide, and is connected with the overfold of the flysch deposits on the Piedmont area. In the flysch deposits greater values may be observed. Repeated depth calculations of reflection seismical materials have shown that the apparent "time" elevations disappear, thus the substratum surface takes a consequent monoclinal dip towards SW.
The problem presented above is general, and of particular importance especially due to the fact that an opinion prevailed as to an uplifting tendency of seismical boundaries towards SW. However, as it results from the materials mentioned before, the seismical results may be charged with an error caused by application of a wrong velocity distribution. The problem here considered is important where vertical velocity gradients may occur. Thus, all deep bore holes should be used for velocity measurements particularly there, where beds can occur, characterized by great differences in elastic properties.
Summary
Negligence of great changes Ln distribution of seismical mean velocities may lead to wrong interpretation of geological structure. In this connection a real example has been discussed of mean velocities in cross sections of SW-NE direction, through the deep bore holes Jaksmanice and Kańczuga, near Przemyśl, in which velocity loggings were made. The zone of changings is 4-6 km wide, and is connected with the overfold of the flysch deposits on the Piedmont area. In the flysch deposits greater values may be observed. Repeated depth calculations of reflection seismical materials have shown that the apparent "time" elevations disappear, thus the substratum surface takes a consequent monoclinal dip towards SW.
The problem presented above is general, and of particular importance especially due to the fact that an opinion prevailed as to an uplifting tendency of seismical boundaries towards SW. However, as it results from the materials mentioned before, the seismical results may be charged with an error caused by application of a wrong velocity distribution. The problem here considered is important where vertical velocity gradients may occur. Thus, all deep bore holes should be used for velocity measurements particularly there, where beds can occur, characterized by great differences in elastic properties.