Utilising web-based gis application for spatial centrographic analysis of earthquake data

Geographical Information Systems (GIS) have become an essential tool for analyses and calculations because they handle all the events that can be displayed on a map in a digital environment. In this study, the earthquake data obtained by the sensors of the US Geological Survey (USGS) located in many regions of the world have been transferred to the geographical information system and analysed for the detection of the earthquakes' intensified regions via centrography method. The earthquake data of the USGS, which holds the information on earthquakes from the year of 1900 to the present day in a database and shared via web services, has been queried with different parameters and the obtained data has been analysed by using centrography in the geographical information system. In this thesis, a web GIS application was needed in the first place, and modelling was done as to transform the structure of the earthquake data. Later on, the design of the web services to be queried for the earthquake data was investigated, and the code blocks were prepared to provide the necessary communication between the web GIS application and the web services and transform the model to apply the earthquake data. The earthquakes had been classified according to their magnitude while they were shown on the map and they were reflected on a thematic map. Thematic maps are the map types that are generated by classifying the phenomena on the map according to its characteristics and the representation of the phenomena can be based on either a colour scale or a size scale. On this count, the user, who checks the map, can easily distinguish the elements with different values because of the colours and the sizes of the markers. In this study, the earthquakes have been represented with different colours according to their magnitude, and it has been ensured that the users of the application could easily see where the earthquakes are more severe and weaker. Although the human beings may have a general idea of the density points on the map, it has no scientific or statistical significance. The aim of this study is to find the regions where earthquakes are clustered by statistical analysis instead of giving the initiative to the human to define the density regions. There are various methods in geographical information systems for this purpose. Some of them are heat map, centrography and clustering methods. In this study, an iterative algorithm has been developed using the centrography methods to identify the concentration zones of the earthquakes. Centrography is basically a statistical method that aims to find out where a phenomenon is clustered, investigate whether there is any displacement or trend in the density over time and support the decision maker to choose the right decision for the future plans for the region based on the results. The centrography algorithm developed in this study tried to find out the areas, in which the earthquakes occurred frequently. However, since it is not enough to develop only the algorithm, the results obtained in the analyses have also been investigated. The results obtained for this purpose have also been compared with the results of the heat map method, which is another GIS method. The results of the centrography method were expected to show the same zones that are displayed with high temperature value on the heat map. The results show that the centroids generated by the algorithm developed in this study covers the high temperature fields on the heat map.