Wpływy upadów w sejsmice refrakcyjnej
Abstract
INFLUENCE OF DIPS IN THE REFRACTION SEISMIC
Summary
When interpreting the polystratal system as a simple two-stratal one we make some mistakes in estimation of dip and of velocity of the refractor studied (in the Polish geophysical literature instead of "refractor" the term "refracting surface" as preferred), due to omission of influence of the overlying strata.
In the case of three-stratal system (V0, V1, V2) the analysis of which is discussed in this paper, when omitting the dip φ of the upper refractor, we obtain for the lower refractor a dip ψc and a velocity Vc, different from true dip ψ and velocity V2 in the three-stratal system.
For dips normally found during the refraction works, the relation of these dips amounts:
(ψc-φ)/(ψ-φ) = (tg i02)/(tg i12) = k
where
sin i02 = V0/V2
sin i12 = V1/V2
This relation, as may be seen, represents a stable value for given system.
Similar mistake made when interpreting the velocities, may be expressed in a relation
Vc/V2 = cos (ψc-φ) : cos (ψ-φ)
The above presented equations or their graphical expressions are useful in changes of one system into second system and allow to avoid the troublesome interpretations or nomograms used during interpretations of polystratal systems.
Summary
When interpreting the polystratal system as a simple two-stratal one we make some mistakes in estimation of dip and of velocity of the refractor studied (in the Polish geophysical literature instead of "refractor" the term "refracting surface" as preferred), due to omission of influence of the overlying strata.
In the case of three-stratal system (V0, V1, V2) the analysis of which is discussed in this paper, when omitting the dip φ of the upper refractor, we obtain for the lower refractor a dip ψc and a velocity Vc, different from true dip ψ and velocity V2 in the three-stratal system.
For dips normally found during the refraction works, the relation of these dips amounts:
(ψc-φ)/(ψ-φ) = (tg i02)/(tg i12) = k
where
sin i02 = V0/V2
sin i12 = V1/V2
This relation, as may be seen, represents a stable value for given system.
Similar mistake made when interpreting the velocities, may be expressed in a relation
Vc/V2 = cos (ψc-φ) : cos (ψ-φ)
The above presented equations or their graphical expressions are useful in changes of one system into second system and allow to avoid the troublesome interpretations or nomograms used during interpretations of polystratal systems.