Frontiers in Geotechnical Engineering (FGE), Volume 4, 2016 www.seipub.org/fge doi: 10.14355/fge.2016.04.001 1 Modelling of Reverse Dip‐Slip Faults Using 3D Applied Element Method Mohammad Ahmed Hussain 1 , Ramancharla Pradeep Kumar 2 1 Department of Civil Engineering, Alhabeeb college of Engineering and Technology, Damergidda(v), Chevella, R. R District ‐ 501503, Telangana State, India 2 Earthquake Engineering Research Center, International Institute of Information Technology Hyderabad, Gachibowli, Hyderabad, India 1 ahmediiithyd@gmail.com; 2 ramancharla@research.iiit.ac.in Abstract It has been observed that near fault ground motion consists of different characteristics compared with the far fault ground motions. In this paper, the near fault ground motion due to dip‐slip surface faults using 3D Applied element method is studied. Using AEM, the crack initiation and propagation can be modelled in reasonable time by using the available parallel computing power. The main advantage of this method of modelling is the ability of crack initiation based on the material failure and propagation of crack till the collapse. This method is used for studying the spatial variation of ground motion due to seismic bedrock displacement at the bedrock level. The influence of dip angle and the presence of lower velocity layer on the near fault ground motion is also studied. It has been noted that in all cases with different fault dip angle, there is greater ground motion on the hanging wall side compared with the ground motion of foot wall side. This effect is due to two important reasons. First, the points on the hanging wall are closer to the fault plane and secondly, the trapped seismic energy in the wedge shape hanging wall leads to multiple reflections. The results from different dip angles indicate that the near fault ground motion is sensitive to the dip angle. Variation of peak ground acceleration with site natural period has also been studied. Systematic decrease in the response is seen with the increase in the site natural period. Keywords Applied Element Method, Near‐Fault Ground Motion, Fault Motion, Dip‐Angle Introduction The most seismological research on the investigation of ground motion due to fault dynamics has been limited to faults with a high degree of symmetry, such as faults in homogeneous whole spaces and vertical strike‐slip faults due to computational and theoretical constraints. Much can be learned from such studies. However, there are both observational and theoretical arguments that the dynamics of faults with asymmetrical geometry are both qualitatively and quantitatively different from those of symmetrical faults. In particular, there is observational evidence that symmetry of ground motion with respect to fault‐slip direction is lost when a fault does not have a vertical dip. The M7.6 1999 Chi‐Chi (Taiwan) earthquake will undoubtedly be recognized as one of the most significant earthquakes for the science of seismology, due to the unprecedented amount of high‐quality near‐ source data that it generated (Lee et al., 1999). This wealth of data not only allows more precise determination of faulting models of this event, but also addresses new questions concerning faulting and dynamics. In particular, this event allows the verification of many pre‐dictions of ground‐motion behaviour in the near source area of dip‐ slip faults, where data have been especially scarce to date. In this paper, it is shown that many of the observations of the near‐source displacements and peak accelerations can be explained as simple consequences of the asymmetry of the dipping fault geometry. Closer to the subject of the Chi‐Chi earthquake, it has been previously argued that the dynamics of dip‐slip faults (especially those that intersect the free surface of the earth) are strongly affected by their fault geometry (Brune, 1996; Oglesby et al., 2000; Shi et al., 1998; Oʹ Connel et al., 2007). In particular, these studies showed that in comparison with vertical strike‐slip faults, dip‐slip faults exhibit many unique features associated with their asymmetrical geometry. These effects include reflections from the free surface that cause a feedback between the rupture and radiation processes, leading to thrust faults having greater dynamic