nd 
I 
he 
ed 
ne 
the 
the 
the 
ye, 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B7. Istanbul 2004 
  
Figure 3. The number of stories of the buildings in the studied 
area 
4. GIS STUDIES 
4.1 Processing of Seismic Data 
Data of the seismic trace obtained at intervals of 1 m were 
filtered using the 30-100 Hz band pass filter. Digital filtration is 
the most optimum approach to analysing seismic data 
(Campanella, R. G. and Stewart, W. P., 1991; Campanella R. G. 
et all, 1989). The average shear wave velocity (Vsav) was 
determined using the first and the last reference signals. 
4.2 Determination of Fundamental Vibration Period Using 
GIS 
Various techniques have been used in applications of 
determination of earthquake risks and micro-zoning based on 
GIS in accordance with the variation of the shear wave velocity 
(Huntera, J. A. et all., 2002). Map of fundamental vibration 
period of the ground (Tj) is one of the maps used for 
determining regional earthquake risk that makes use of the 
shear wave velocity. 
Fundamental vibration period of the ground (T;) is determined 
using the following equation. 
4xH; 
T, a | (1) 
where H = the thickness of the alluvial ground focal length 
V = the average shear wave velocity 
Determination of the fundamental vibration period of the 
ground depends on two variables. 
l. (Va): A map of the average shear wave velocity was 
obtained by using the SCPT technique. The average shear 
wave velocity was determined to vary between 100-340 
m/s for all the seismic record depth in each of the 32 
different points (Figure 4). 
1139 
  
Figure 4. Shear wave velocity map of the studied area 
2. Thickness of the alluvium (H): A large part of the 
studied area is located over a ground composed of the new 
alluvium, containing loose gravel, sand, silt and clay, 
carried away by the Porsuk River. Electric resistivity 
method has been applied in 112 locations by DSI with a 
depth of nearly 60 m. (Azdiken S. and Catalyürekli E., 
2001; Azdiken S. and Catalyürekli E., 2001) (Figure 5). 
^ 
  
1 i ; 
Figure 5. Locations of geophysical resistivity measurements 
The geophysical measurements obtained revealed that, the 
thickness of the alluvium in the studied area varied between 10- 
25 m, and that the northern east part reached a thickness 
varying between 10-15 and 15-25 due to the over-storage of 
materials carried away by the Porsuk River (Azdiken S. and 
Çatalyürekli E., 2001; Azdiken S. and Çatalyürekli E., 2001). 
A three-dimensional model of thickness of alluvium was 
obtained by using geophysical resistivity data. Values of the 
thickness of the alluvium scattered across the study area have 
been presented in this model (Figure 6).