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Figure 1. System design 
This study is divided into short-term and long-term objectives. 
The short-term objective is to develop a prototype system that is 
capable of being expanded to a larger system that links multiple 
datasets and tools. The long-term objective is to extend the 
prototype system and develop more Web services and portal 
framework for efficient access to data and tools. In this study, 
geodetic and geophysical data, software packages and scientific 
applications were compiled and a system has been developed. 
There had been two primary aims in this development. The first 
is to create a tool as part of the system services which will 
compute strain by geodetic GPS velocities and earthquake focal 
mechanisms data. The second is to make the users retrieve maps 
on the Internet, which is one of the realizations of integration 
tools of the system design. The study combines two software 
programs ArcIMS [2] and GMT [3] with FORTRAN programs 
in ASP.NET environment. 
In this study, the developed system brings the complex strain 
analysis procedure developed by [4] and [5] to a level that can 
be used by anyone efficiently and effectively using Web 
services approach. The calculation process of strain programs 
and the other codes created during this study is pretty much 
complex. There are over 30 programs to be able to use 
mentioned method and to see the results obtained. Some 
modifications were done to increase portability and IO 
performance. There were a number of places where the codes 
require user interaction by entering some input parameters using 
command line. These codes were removed, and input 
parameters were arranged to be entered from the graphical user 
interface. FORTRAN codes were compiled in Windows OS and 
performed batch file scripting to run all programs as one 
program. Creating Web service and connecting the application 
to ArcIMS were the next steps of the study. 
ArcIMS is an internet mapping software. It brings GIS to the 
Web by providing the ability to generate maps on the fly and 
also integrate data from different sources for display, query, and 
analysis. Interactive maps served with ArcIMS include maps 
With layers that can be turned on and off, or with features 
containing attributes that can be queried. A web browser is just 
needed by the user, and the database is maintained on the server 
side. ArcIMS uses ArcXML to receive and respond to requests 
from the client. ArcIMS needs a Web server that can be 
extended to run Java code. Apache Web Server was used in the 
implementation. ArcIMS installation also needs a servlet engine 
installation. Servlet engines extend Web servers with a common 
API and allow them to process Java code. J2SDK was also 
installed in a Windows Server 2003 machine for ArcIMS. GMT 
is a visualization tool widely used in the Earth science. GMT is 
an open source collection of about 60 UNIX tools, which was 
developed by the School of Ocean and Earth Science and 
Technology (SOEST) of University of Hawaii. It allows users to 
manipulate datasets and produce images. 
2. CODE DEVELOPMENT 
2.4 Computational Background 
In the study, there are two types of geospatial data: geodetic 
velocities provided by GPS and earthquakes’ focal mechanisms. 
A file-based database is used in the study. There are three input 
files to run the algorithm for strain calculation. They are ASCII 
files which have columns and rows. Columns have fixed-width 
data formatting and the files do not include header lines. The 
two files are the data files and the other one is the geometry file. 
There is no relationship or link between these files. Geometry 
file is semi-static. It is modelled considering Turkey’s active 
faults, tectonic settings and seismicity. Users can create a new 
file based on the default geometry file changing the grid size of 
the algorithm. Focal mechanisms file includes all records (since 
1976) for entire Turkey. A user by selecting area using latitude 
and longitude boxes on the interface can create a new focal 
mechanisms file. And the GPS file can be uploaded by the user 
to the system using web interface. Though the system is uses a 
static GPS file in its current form. Users can perform the 
inversion using only focal mechanisms data or only GPS data or 
both together. Then the output files are reformatted and image 
files are created by reading each line of these files. First request 
by the user creates a directory with unique id using time, then 
the input files, exe files which run the strain calculation 
algorithm and all output files are stored in that directory. For a 
selected 0.5 degree grid size, 2500 image files (each 1 kb in 
size) are stored in the directory to be used as layers of ArcXML 
file. 
2.2 Data for Input Files 
GPS velocity data are related to Marmara region of the country 
which involves strike slip faulting. The area has a high seismic 
hazard and risk because of the region's tectonics. GPS data 
consists of the information related to 65 GPS points including 
longitude and latitude values, eastward velocities, northward 
velocities, uncertainties of eastward velocities, uncertainties of 
northward velocities, and correlation between eastward and 
northward components. A program written in C language, 
which assigns number of rotation values to the GPS points was 
used for the creation of the GPS input file. 65 GPS velocities 
come from GPS campaigns performed between the years of 
2003 and 2005 in Marmara region by Geodesy Department of 
Kandilli Observatory and Earthquake Research Institute of 
Bogazici University (BU). These campaigns were performed by 
a collaborative project among BU, MIT (Massachusetts Institute 
of Technology), TUBITAK-MRC (Turkish Scientific and 
Technological Research Council - Marmara Research Center), 
GCM (General Command of Mapping), and ITU (Istanbul 
Technical University). 
A focal mechanism solution is the result of an analysis of 
waveforms generated by an earthquake. An earthquake’s focal 
mechanism provides important information, including the origin 
time, epicenter location, focal depth, seismic moment, and the 
magnitude and spatial orientation of the moment tensor. 
Earthquake focal mechanisms data is provided by Global 
Seismology Centroid Moment Tensor catalog. This catalog 
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