Geophysical Abstracts 152 January-March 1953

30 GEOPHYSICAL ABSTRACTS 152, JANUARY-MARCH 1953
point source can be approximated by an explosion at a sufficient depth. Proof
is presented that for distances r, greater than the length X of the wave, the
amplitude of seismic wave can be represented by the formula A=Ao/r. Travel-
time curves in the vicinity of the point source, for r\ they can be assumed to be rectilinear. These fundamental relations derived
for amplitudes and travel-time curves of waves caused by harmonic source, can
be extended to waves produced by impulses, generating quasi-sinusoidal
vibrations. Author's summary, 8. T. V.
14275. Kosminskaya, I. P. Interferentsiya seysmicheskikh voln, vyzyvayemykh
garmonicheskim istochnikom [Interference of seismic waves from a
harmonic source]: Akad. Nauk SSSR Izv., Ser. geofiz. no. 4, p. 33-54,
1952.
The interference of two seismic waves, sufficiently distant from the source of
vibrations to be considered as plane, is discussed and formulas are given for the
resulting amplitudes and for the phase of the composite wave. The derived
formulas are then extended to the case of several waves, and a graphoanalytic
method is suggested for construction of the resulting amplitudes and travel-time
curves.
By analysis of different shapes of the travel-time curves and of the curves of
amplitudes of composite waves, examples can be shown of the dominant wave
that has a greater or smaller velocity than the others. In certain cases this
procedure makes it possible to find individual components from the seismograms.
Master charts are suggested for such analysis. Indices are also established
which show when a recorded seismic wave is a composite one, resulting from the
interference of several simple waves. S. T. V.
INSTBUMENTS AND METHODS OF OBSERVATION
14276. Borisevich, Ye. S. Registriruyushchiye pribory dlya seysmicheskikh
stantsiy [Recording apparatus for seismic stations]: Akad. Nauk SSSR
Geofiz. Inst. Trudy no. 14 (141), p. 53-58,1952.
This is general discussion of good recording equipment. The most important
feature is said to be uniform rotation of the drum; variation in the length of the
minute must be not greater than 0.3 percent. It is important to have both
mechanical and optical recording. Precautions in installation and rules to be
followed in the maintenance of the apparatus are given. Most of the article is
devoted to a description and criticism of recording apparatus of Russian
origin. 8. T. V.
14277. Bwing, Maurice, and Press, Frank. Further study of atmospheric pres­
sure fluctuations recorded on seismographs: Am. Geophys. Union Trans.,
v. 34, no. 1, p. 95-100,1953.
The predominant background disturbance on a long-period vertical seismograph
is removed by providing compensation for atmospheric pressure fluctuations. A
seismically-compensated, long-period microbarovariograph for study of pressure
oscillations in the range 20-2000 sec is described. Comparison of records from
the pressure-compensated seismograph and the seismically-compensated micro­
barovariograph indicates that no significant ground motion is caused by direct
coupling of atmospheric pressure fluctuations to the earth. Sample records are
shown. Authors' Abstract