“7 th AGILE Conference on Geographic Information Science” 29 April-1May 2004, Heraklion, Greece Parallel Session 7.3- “Decision Support Systems / Risk Management II” 645 Comparison of CPT Based Liquefaction Potential and Shear Wave Velocity Maps by Using 3-Dimensional GIS Muammer Tün, Uğur Avdan, Metin Altan, Can Ayday Anadolu University, Satellite and Space Sciences Research Institute Iki Eylul Campus, 26470 Eskisehir, Turkey {mtun, uavdan, maltan, cayday}@anadolu.edu.tr phone: 222-321-3550; fax: 222-323-9129 SUMMARY Geological and geotechnical researches and studies according to safe construction and proper civilisation must be done before the preparation of construction plans of urban area. This is the first step in the earthquake hazard analysis. The results obtained from these studies have been used as input for earthquake hazard risk evaluation. Utilisation from 3-Dimensional GIS, instead of 2 Dimensional in this stage by using drilling data and analysing them gives more reliable results. Nowadays it is known that, micro-zoning studies and preparation of earthquake risk scenarios depend on these studies are generally used in GIS technology. The overall studied area is nearly 128 hectares and belongs to Seismic Region II. of General Earthquake Risk Map of Turkey. Seismic Cone Penetration Test (SCPT) studies were done at 25 different locations. Cone resistance (q c ), sleeve friction (f s ) and friction ratio (R f ) values were obtained from 279 different layers. CPT based liquefaction map of the interested area were prepared by using these parameters. In addition to that, shear wave velocities (V s ) of different depths were obtained from the same area. Shear wave velocity data of the soil were used for the preparation of shear wave velocity distribution map of the area. All these data were used for making comparison between CPT based liquefaction potential and shear wave velocity distribution model by 3-dimensional GIS techniques. Comparison has indicated that, volumetric distribution of shear wave of soil which has velocity less than 180 m/sec exists between the surface and 5 m depth. On the other hand, liquefiable zones are seen mostly below this depth. Although some overlapped regions were detected with 2-dimensional analysis, it is concluded that, soil which has low V s may amplify ground motions significantly generally exists between 0 m to 4 m depths and liquefiable zone exits between 4 m to 7 m depths. This result have been obtained only by using 3-dimensional GIS. KEYWORDS: CPT, liquefaction potential, shear wave velocity, 3-dimensional GIS INTRODUCTION A methodology for assessing seismic risk study includes regional and local hazard and vulnerability of physical properties. As a first step, earthquake hazard analyses covers the determination of seismic condition of the area and engineering geological parameters of the soil which was obtained from the same area. These values would be used as input for the vulnerability studies sometimes called as loss of estimation. Earthquake hazard studies must be done before the vulnerability investigations. The results of the studies are the main basement for loss estimation studies. Technological development has put forward using computers and related softwares for the study. Geographic information system which is defined as using geographic data for modelling and analysing is the most powerful tool for preparation of these maps. GIS designed specifically for geological work need to be fully three-dimensional, so that each data object is characterised by its location in space with three spatial coordinates (Bonham-Carter, 1994). In