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SEISMIC
EXPLORATIONS
› SEISMIC EXPLORATION OF REFRACTION TYPE
The seismic exploration of refraction
type is among the most diffused and
used active seismic methods. This
type of survey has the purpose to determine
the thickness of the overburdens
(aerated) above a rigid sub-layer
and reconstruct a seismic stratigraphic
sequence in terms of apparent longitudinal
speed. If carried out according
to more sophisticated calculation
methods, it can be used to intercept,
measure and characterize geo-structural
profiles. Seismic exploration of
refraction type is carried out by placing
equidistant geophones in line on
the ground, and generating seismic
pulses through mechanical “inputs”.
Then the travelling times of the pulses
that once penetrated in the ground
are refracted nearby the lithological
passages at different density, will be
measured.
› SEISMIC EXPLORATION OF REFLECTION TYPE
The seismic exploration of reflection
type, which is extensively used in oil
explorations, is also used nowadays
to obtain detailed information on surface
soils. Due to the high resolution
of the survey, it is used to define the
development of geological structures
in the sub-soil, defining the shapes,
sizes and positions. The prospecting
is carried out by placing high frequency
geophones in line and close to each
other, sending seismic pulses through
energy (also at high frequency) and
by measuring the travelling times of
the waves that, once penetrated in
the ground, are reflected by the uneven
surfaces that delimit the lithological
passages with net impedance
contrast.