Geophysical Abstracts 152 January-March 1953

SEISMOLOGY 35
velocity linearly increasing with depth; velocity an exponential function of
depth; velocity a linear function of the distance from the observation point to
shot point. Travel-time curves can be constructed on ordinary coordinate paper,
(as Zlotnik's curves) or transformed to bilogarithmic scale, the method fol­
lowed by Bugaylo. The advantages of the latter method are greater precision
and ease of construction. Sample charts are included in the study. S. T. V.
14294. Yepinat'yeva, A. M. O nekotorykh seysmicheskikh volnakh s bol'shimi
vremenami prikhoda [On some seismic waves with late times of
arrival]: Akad. Nauk SSSR Izv., Ser. geofiz. no. 6, p. 21-38,1952.
In seismic reflection surveys, quite often waves are recorded with exceedingly
late times of arrival. If such waves are interpreted as simple reflections, the
reflecting boundaries should be at depths of 200 km or more, which is im­
probable. The author analyses dynamic characteristics of these waves, pri­
marily' the variation of amplitudes with distance, using as a criterion the ex­
pression At (where A=amplitude and £=time of arrival). If this product in­
creases or remains constant over a short distance, thfe it can be concluded that
the waves are not simple reflections. As an additional criterion the function
log At, constructed for different values of distance, can be also very useful. Only
strong waves which can be clearly traced over long distances should be con­
sidered. In absence of such waves of stable character, not much reliance is to
be placed on the seismic reflection method. S. T. V.
14295. de Caleya, Juan, Gloss, Hans, and Durbaum, Hansjiirgen. Zur Beriick-
sichtigung der Brechung in de Reflexionsseismik [The recognition of
refraction in seismic reflection surveying] : Erdol u. Kohle, jahrg. 5,
heft 12, p. 765-768, 1952.
A new graphoanalytic method of analyzing seismic reflection data is presented
that takes into account the variation of seismic velocity and is applicable to
inclined strata. The method is discussed first for the case of two formations
with different seismic velocities and later extended to any number of layers. It
is illustrated by an example of a profile composed of four layers with different
velocities in each. S. T. V.
14296. Mota, Lindonor. Corregao dos tempos em refracjio sismica [Weathering
corrections in seismic refraction]: Univ. Brasil Escola da Minas Rev.,
ano 16, no. 5, p. 35-38, 1951.
Calculation of weathering corrections for cases of one or raore inclined
refracting layers is described. M. C. R.
14297. Bediz, P. I. Interpretation of seismic data on locating reefs in Alberta:
World Oil, v. 136, no. 2, p. 86-90,1953.
Specialized instrumental, shooting, and interpretive techniques are required
to locate reefs in the Alberta Devonian formations, which usually give poor
reflections characterized by phasing and splitting, abnormal step-out, and the
appearance and disappearance of reflections. Pre-Devonian faulting, the lack of
Devonian reflections in areas of other good reflections, and isopach maps for
time differences between Cretaceous horizons and the top of the Devonian may
all indicate reefs. However, similar conditions can be caused by other sources
such as the Paleozoic unconformity. D. F. B.