Geoscience Reference
In-Depth Information
led to subsidence of the continental crust over all regions behind the south Aegean.
The region is mainly under pure shear stress from an internally deforming counter-
clockwise rotation of the Anatolian Plate relative to the Eurasian one. There is a multi
disciplinary research report in the literature concerning the plate interactions through
the whole Arabia-Africa and Eurasian plates performed for several periods (Reilinger
et al., 2006). Figure 1 shows the result of this study, performed by Reilinger et al. The
Aegean Region has been suffering active N-S extensional tectonics, under the control
of two main motions. One of the motions is the westward escape at a rate of 2025 mm/
year of the Anatolian plate, bound by the North Anatolian Fault and East Anatolian
Fault, and intersecting at the Karliova depression of the East Anatolia. The westward
motions change direction in West Anatolia with a rather abrupt counter-clockwise ro-
tation towards the southwest over the Hellenic Trench. The other motion is the N-S
extension of the Western Anatolian and the Aegean plates with a rate of about 36 cm/
year. As a result of these motions a group of E-W trending grabens have been develop-
ing. These grabens are bound by E-W trending normal fault zones which extend about
10,0150 km. These fault zones are generally segmented and each segment is no longer
than 810 km (Yilmaz, 2000).
The complicated geology of the region has given rise to disagreements on the
source or beginning of the extension of the region. McKenzie (McKenzie, 1978)
suggests the beginning time of the extension as 5 Ma, while by other researchers
have suggested 1311 Ma (Mercier, 1989). This variety in the suggestions concern-
ing the beginning of the N-S extension for the Aegean Region may be due to on
the insuffi cient accuracy of the methods used to determine the beginning time or
lack of information about the previous geological researches that preclude accurate
estimations.
Consequently, the result has been a focus of the geological investigations on
the Aegean Region in order to understand the tectonics of the area. Geodesy and
geodynamics can also contribute additional information (Segall and Davis, 1997).
Geodesy builds its investigations on the information gathered from the seismologi-
cal studies. Therefore, interpretation of earthquake distributions, determination of
focal mechanisms, and fi eld studies that aim to defi ne fault traces provide valuable
data for geodetic crustal deformation studies. Thus, the project area that is to be
monitored with geodetic techniques has to be evaluated in terms of the project area's
seismicity. A complete picture for deformation monitoring studies using geodetic
techniques has to be formed including defi nitions on tectonics of the study area, net-
work design regarding to the geological and geophysical parameters of the region,
and approaches to the combination of different geodetic techniques. The chapter
discusses the possible extensions in the size of the network depending on the fault
characteristics. Monitoring two or more faults together, for instance, can be a better
solution to understand the characteristics of the region in some cases so the study
area needs to be extended during the geodetic observations. This chapter uses the
formulations in one-dimensional fault model with two parameters standard strike-
slip model of dislocation theory in an elastic half-space for selecting suitable site
locations of the network.
