USE OF RECORD CHARACTER IN INTERPRETING 
RESULTS AND ITS EFFECT ON DEPTH CAL- 
CULATION IN REFRACTION WORK! 
T. L. ALLEN? 
San Antonio, Texas 
ABSTRACT 
In seismograph exploration, the author nas encountered ac ustic horizons which do 
not transmit seismic energy readily. The first impulse on the seismogram has a short 
period with small amplitude, and requires considerable energy to make it apparent at 
long distances. This horizon is underlain by one of slightly higher velocity which trans- 
mits the energy readily and has a distinctly different wave form. On account of the 
difficulty of energy transmission, the horizon which has the small “forerunner” wave 
might be interpreted as a lens and not a continuous horizon. By making use of the 
character of the wave form on the seismograms, the two horizons may be definitely 
identified, and the one which is a poor conductor of energy definitely proved to be a 
continuous acoustic horizon. 
INTRODUCTION 
This paper covers a short discussion of a problem encountered in 
refraction work done in Venezuela during 1931. The work was done 
by the International Petroleum Engineering Corporation of New 
York, using electrical seismographs and radio equipment built by the 
Petty Geophysical Engineering Company of San Antonio, Texas. The 
writer was in charge of the party in the field. 
The problem to be considered involved an interpretation of re- 
sults in an area where an acoustic horizon transmitted the seismic 
energy poorly. Referring to profile A, Plate 1, it is evident that there 
are four acoustic horizons involved, with velocity values of approxi- 
mately 2,000, 2,160, 2,580 and 6,510 meters/second, the first three 
being sedimentary, while the fast one represents the igneous base- 
ment. There were several other profiles shot in the same general area 
as profile A and all of them had the same general velocity values. 
Profiles B, C, and D were approximately 50 kilometers from profile 4, 
and the sedimentary horizons had become thinner in this distance. 
Several profiles were shot in the distance between the two areas, and 
' Published by permission of International Petroleum Engineering Corporation, 
80 Maiden Lane, New York, N. Y. Read before the Association at the Oklahoma City 
meeting, March 24, 1932. 
2 Field manager, Petty Geophysical Engineering Company. Introduce1 by. L. W. 
Blau. 
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