The FAULT RUPTURE PROPAGATION phenomenon, spreading from the base rock through different layers of soil, is a matter of concern in many natural and man-made soil structures. The focus of this paper is to investigate reverse FAULT RUPTURE PROPAGATION through two layers of sand deposits by means of numerical modeling. For this purpose, analyses are carried out for different permutations of the three typical materials: dense sand, medium dense sand and loose sand, considering five FAULT dip angles, 30, 45, 60, 75 and 90 degrees. The validity of numerical model was verified by simulating an experimental model of homogeneous soil layer subjected to reverse FAULTing. Further to the general trends found in FAULT RUPTURE PROPAGATION in a single layer of soil, special attentions are devoted to the refraction of FAULT path in the interface of two materials as well as its concavity in the continuation. Moreover, four patterns of FAULT rapture PROPAGATION in two-layered sands, depending on their arrangements and FAULT dip angles, were concluded from the results.

Construction in near FAULT regions is of specific importance for which safety should be considered against seismic FAULTs. FAULT RUPTURE zone is a region that civil construction receives highest damage from near FAULT zone effects such as surface fractures, strong ground motion, displacement and landslide in the regions of great slope and rough topography. In this study, first, the three dimensional topography and slope map of the studied area are prepared. The FAULT RUPTURE zone of North Tehran FAULT is calculated after developing the FAULTs density and magnitudes gained from three probable mobile scenarios. Present study suggests a FAULT RUPTURE zone of 2.2 to 1 km for North Tehran FAULT.

The destructions of earthquakes in Turkey and Taiwan (1999) have increased the interest of investigation on structures behavior in surface FAULT RUPTURE PROPAGATION. Therefore, many studies have been accomplished to investigate the FAULT RUPTURE and shallow foundations interaction. Based on the fact that a lot of structures are constructing and they have the possibility of facing FAULT emergence hazards due to the uncertainty in exact locating of surface FAULT emergence, the investigation on surface FAULT RUPTURE hazards can give a better insight to explicit this issue and mitigate the damage to constructions adjacent or in active FAULT zones. In this research, numerical investigations on surface FAULT RUPTURE hazards based on the evaluation of earthquake's field studies and seismic codes limitations for constructions in active FAULT zones have been employed. Based on field studies observations, four different FAULT zones with different levels of hazard possibility for structures have been obtained. Some of the field studies results have been reviewed in this paper. For numerical studies, the two-dimensional, finite element software (Plaxis) was employed to study the surface FAULT RUPTURE mechanism beneath the foundation in four different locations. In the mentioned Plaxis model, a rigid foundation with breadth, B=20 and embedment depth, 𝐷 = 0 𝑚 was used. The model height was 25 m, and in order to model the bedrock, 5 m layer with Vs= 1000 m/s was considered beneath the model. It should be mentioned that the FAULT has a dip angle, α =60 ° at the rock– soil interface, the length of FAULT PROPAGATION upward from the bedrock is 25 m and the fixed part of the model is 75 m. After locating the FAULT RUPTURE trace on the ground in free-field condition, the foundation was located in four different positions in respect of free field and bearing pressure, q=90kpa (9-storey building) was imposed on all of them. Foundation rotations were calculated in these models and compared together. By moving the foundation toward the foot wall, the rotation amount decreased. In the following, to investigate the effect of load on reverse FAULTing, the bearing pressure was increased to 360 kpa for two foundation locations and the results discussed. Decreased foundation rotation and soil uplift in surrounding area were really noticeable. In order to investigate the seismic code limitations, two different models were made. The foundation was located in hanging wall at the distance of 15 m from free field location. In these models, bearing pressure of 90 and 360 kpa were examined. In this case, by increasing the bearing pressure, the amount of foundation rotation increased. The field studies results indicate, foundation location and structure weight have important impact on structure damages during surface FAULT RUPTUREs. As mentioned, these results have been achieved in this paper. Briefly, the results of numerical models demonstrate that seismic codes limitations such as setback do not have necessarily safe construction outcome.

Ground differential movements due to FAULTing have been observed to cause damage to engineered structures and facilities. Although surface FAULT RUPTURE is not a new problem, there are only a few building codes in the world containing some type of provisions for reducing the risks. FAULT setbacks or avoidance of construction in the proximity to seismically active FAULTs, are usually supposed as the first priority. In this paper, based on some 1-g physical modelling tests, clear perspectives of surface FAULT RUPTURE PROPAGATION and its interaction with shallow rigid foundations are presented. It is observed that the surface FAULT RUPTURE could be diverted by massive structures seated on thick soil deposits. Where possible the FAULT has been deviated by the presence of the rigid foundation, which remained undisturbed on the footwall. It is shown that the setback provision does not give generally enough assurance that future FAULTing would not threaten the existing structures.

Due to the problems and high cost of real-scale experimental studies and on the other hand, the ability of small-scale models in geotechnical centrifuges to establish physical similarity and take into account the real stresses in the model for a correct understanding of deformations and RUPTURE mechanisms, major experimental studies on the phenomenon of surface FAULTing has been done using by geotechnical centrifuge. In this research, the concept of physical modeling with a geotechnical centrifuge, scale rules, constraints, and sources of error in simulating the interaction of dip‐slip FAULT with underground tunnels and shallow foundations are investigated. Finally, by minimizing modeling errors, the interaction of reverse FAULT with underground tunnels, as critical transport infrastructure, and the shallow foundation is simulated. The results showed that in reverse FAULT PROPAGATION in sandy soil when the RUPTURE reaches the surface, its dip angle decreases, and at the ground surface, shear RUPTUREs and tension cracks are created which can damage structures and infrastructures. The presence of the tunnel in the RUPTURE path causes the FAULT RUPTURE path to change and the FAULT RUPTURE zone to increase at the ground surface, which can affect the performance of surface structures and buried structures adjacent to the tunnel. In the PROPAGATION of reverse FAULT RUPTURE, the presence of the surface structure on FAULT outcrop, overburden pressure due to the structure, causes the RUPTURE path to deviate to the right corner of the foundation and the structure to rotate. Besides, on the right side of the foundation, a FAULT scarp was observed, which was consistent with field observations in previous earthquakes with surface FAULT RUPTURE.

IDuring large earthquakes, a soil deposit overlaying an active FAULT is suspected to experience quasi static differential settlement produced by PROPAGATION of bedrock FAULT rupturing. Such differential surface dislocations can cause severe damage to engineering framed structures. Although there is partly extensive literature in this field, in most previous studies, super structures are not considered in the analysis directly. This paper investigates the interaction of a frame structure located on top ofa soil sediment with a reverse FAULT rupturing. For this purpose, a series of reduced scale 1 g box tests with a steel frame structure were conducted. Then, the same related numerical models were calibrated and validated using physical modeling results. To compare different structural system behavior against surface FAULT RUPTURE, two types of steel framed structure including moment resisting frame and concentric braced moment resisting frame were selected in the numerical analysis. A brief sensitivity analysis on structure position relative to FAULT outcrop is performed using numerical Finite Element (F. E. ) method for both types of structural systems. Different responses for sediment and structure are considered. The results showthat deformation mechanism of structural elements in these two systems are basically different. Based upon the results of this research, the moment frame is suspected to have more severe structural damage or even complete destruction.

In an era where underground transportation infrastructure is increasingly vital, the construction of tunnels across FAULT lines has become a necessary challenge. This study addresses the critical issue of assessing the impact of FAULT RUPTUREs on shallow tunnels, with a particular emphasis on the variability of soil parameters. We employ the Stochastic Finite Element Method (SFEM), providing a robust framework for simulating the unpredictable nature of soil properties in shallow tunnels under the impacts of surface FAULT RUPTURE hazards. Our approach highlights the significant influence of soil parameter variations in the analysis of tunnel vulnerability during FAULT RUPTUREs. The findings offer valuable insights for the design and safety assessment of tunnels in seismically active regions, contributing to the advancement of geotechnical engineering practices in the context of FAULT RUPTURE hazards. Specifically, the maximum stress values demonstrated substantial increases of 77 and 100% when compared to the 0.5-meter case for the 1.0-meter and 2.0-meter scenarios, respectively.

Recent earthquakes have shown that, besides the seismic forces, the interaction between FAULTs and structures could cause extensive damage to the surface and underground structures. Field observations showed that the need for design measures and regulations for FAULT loading due to FAULT movement in areas with active FAULTs seems necessary. In this study, the three-dimensional finite element model in Abaqus finite element program to study the behaviour of a 9-story steel structure with a moment frame system based on three types of mat foundations, piles group, and diaphragm walls was used on sandy soil. The performance of the structural-foundation system was evaluated taking into account the structural and geotechnical performance goals such as the drift ratio of floor levels, displacement of the foundation and distribution of bending moment and shear force along with the pile and foundation. In this study, the position of the foundation relative to the FAULT line and the foundation type were considered as key parameters. The results of the analysis showed that the best performance in reducing the ratio of the permanent drift ratio of the floors related to the structure with the diaphragm wall system. This was in the case that the edge of the foundation is tangent to the FAULT line, this value reaches 1. 62%. Also, in most cases, in small amounts of FAULT movements, the mat foundation system had a smaller difference than the other considered foundation system in this study.

This paper studies the shear zone of North Qazvin FAULT and investigates the location of rural settlements in this area. In selected sections, the presence of transverse valleys along the FAULT made it possible to investigate the evidence of shear zones in which we can see severe crushing in igneous rocks of andesitic and trachyandesitic type, and cataclastic. Moreover, traces of FAULTed and fractured zones (Damage zone) including fractures and small and minor FAULTs were observed. The study also found Intact green tuffs at the end of the shear zone of the North Qazvin FAULT, which was considered as the healthy wall next to the shear zone. According to the field studies and observations of the shear zone of the North Qazvin FAULT in this section, the width of the shear zone was measured at 320 m on the hanging wall of the FAULT. After that, we used common software to compare the location of villages with the RUPTURE zone of ​​the North Qazvin FAULT. The results showed that the villages of Barajin, Hesamabad, Kherman-Sokhteh, Dastjerd-e Olia, Ahvarak, Khoran, Tazarkesh, Kikhanan, Najmabad, Razjerd, Qutbi Miyan, Sperno, Ange, Mazraeh Lat and Mazraeh Kharmanlough are located on the RUPTURE zone of the North Qazvin FAULT. Moreover, 45 villages are located less than 2 km away from the North Qazvin FAULT. Therefore, it is necessary to relocate the villages that are on the rapture zone or change the direction of future developments of these villages outward, away from the RUPTURE zone. For those villages that are located less than 2 km away from the North Qazvin FAULT, with regard to the acceleration of earthquakes around the FAULT and the phenomenon of rock fall in villages, the study proposes retrofitting in future construction.