4 th International Conference on Earthquake Geotechnical Engineering June 25-28, 2007 Paper No. 1583 ZONE OF EXCESSIVE GROUND SURFACE DISTORTION DUE TO DIP-SLIP FAULT RUPTURE Achilleas PAPADIMITRIOU 1 , Dimitrios LOUKIDIS 2 George BOUCKOVALAS 3 , Dimitrios KARAMITROS 4 ABSTRACT This paper studies the zone of excessive ground surface distortion created by a dip-slip active fault rupture propagating from the bedrock through a soil layer during an earthquake. The simulation of the fault rupture propagation through the soil layer is performed via quasi-static numerical analyses using the finite difference code FLAC. The analysis focuses on the geometry of the developing shear band and the distribution of surface displacements. The paper presents results from 28 parametric analyses that quantify the effects of soil type, fault type and fault dip angle in the bedrock. The results of the analyses are presented in the form of charts and equations for the rough prediction of the location and the width of the zone of significant surface distortion, and the estimation of the fault displacement required for the rupture to reach the ground surface. An example of the fault propagation prediction in an actual case is presented for the well documented rupture of the Nikomidino fault (Volvi basin in Northern Greece, 20-6-1978). In practice, these results can be used for the definition of zones where construction is disallowed (set-back limits) and of zones where damage-preventing countermeasures should be considered in the design of light-weight structures and lifelines (e.g. pipelines). Keywords: fault rupture, microzonation, setback limits, lifelines, earthquake INTRODUCTION The design of structures in the vicinity of active faults is one of the most difficult problems of earthquake engineering. An indication of the complexity of the problem is that seismic codes generally require the execution of a specialized study for any structure, even though there is no specific methodology in the literature for performing such a study. Moreover, many seismic codes, including the Greek code ΕΑΚ (2002), refer to a zone where construction is disallowed, but do not specifically define its width and location. Additional difficulties arise when the active fault is buried under a soil layer of significant thickness (e.g. a few tens of meters). In such a case, even if the location (trace) and the characteristic of the fault in the geologic bedrock (type, dip angle β and expected displacement d) are well defined, there are three (3) practical questions that need to be answered: a) Will the fault rupture reach the ground surface and at which location? b) At which zone will the ground surface distortion be prohibitive for conventional construction? c) Will the seismic motion be amplified in the vicinity of the fault and by which amount? In this paper, the emphasis is set on answering the first two questions, since the third cannot be confidently answered without employing large scale seismological monitoring and interpretation. In 1 Lecturer, Dept. of Civil Engineering, University of Thessaly, Greece, Email: apapad@civ.uth.gr 2 Post-Doctoral Researcher, Dept. of Civil & Environmental Engineering, Purdue University, USA 3 Professor, School of Civil Engineering, National Technical University of Athens, Greece 4 PhD Candidate, School of Civil Engineering, National Technical University of Athens, Greece