Supervisors info:
Αλεξόπουλος Ιωάννης Επίκ. Καθηγητής (επιβλέπων), Βούλγαρης Νικόλαος Αναπλ. Καθηγητής, Αποστολόπουλος Γεώργιος Επίκ. Καθηγητής
Summary:
This dissertation aimed at the combined application of Seismic Reflection
technique and Multichannel Analysis of Surface Waves (MASW) for determining
shallow targets of geotechnical interest.
Over the last decade, a plethora of articles has been published, concerning
Seismic Reflection technique and MASW as invaluable tools to determine shallow
targets. Their application is of extreme interest as they constitute efficient
techniques with a high degree of accurate results.
The area in which the investigation took place was the Isthmus of Corinth. In
this specific site, we acquired the borehole summary report, describing the
geological data collected during the drilling (depths at about 50 m), plus the
results of Downhole – Crosshole seismic tests (Edafomichaniki SA), which helped
as to delineate both the shallow targets of interest and the distribution of
shear and compressional waves’ velocities (Vs and Vp respectively). From the
above mentioned, we used the results of only one borehole, as its surrounding
area was suitable for the implementation of both seismic techniques.
Taking into consideration the near surface soil characteristics of the area, a
Noise Analysis took place, in order to determine the subsurface targets and to
establish a spread type appropriate for enhancing the reflector of interest.
Subsequently, a comparative test of seismic sources was conducted, aimed at
finding the best type of source which could designate the subsurface structure
properly. Among the detonator, the buffalo gun, and three sledgehammers of
different weights (8 Kg, 5Kg, 2.5 Kg), we chose the sledgehammer of 5Kg
combined with a 5 Kg plate and the Buffalo gun as sources suitable for our
seismic reflection survey.
Furthermore, we describe the processing sequence of two independent seismic
reflection data sets, acquired with two different sources (sledgehammer –
buffalo gun) and also the processing of MASW data.
In conclusion, the processing of seismic reflection data resulted in the
description of a shallow seismic horizon at the depth of 22 m. Moreover, the
processing of the MASW data set led to the construction of the 2D distribution
of shear waves’ velocities (Vs) for the upper 10 m, certifying the importance
and the efficiency of the technique.
Keywords:
Geophysics, Seismic reflection, MASW, Shallow structures, Geotechnical interest
