Journal of Seismology and Earthquake Engineering
Volume:10 Issue: 2, Summer 2008

The complete microzonation and site response studies require the characterization of subsurface materials considering local subsurface profiles of the site or region. The general site characterization comprises of the evaluation of subsurface features, material types, material properties and buried/hollow structures, by which it is determined whether the site is safe against earthquake effects. In this study, an attempt has been made to characterize the Bangalore Mahanagar Palike (BMP) area of about 220km2 using the shallow geophysical method, Multichannel Analysis of Surface wave (MASW), which identifies each type of seismic wave on a multichannel record using the refraction survey and produces shear-wave velocity (Vs) profiles. The study area of BMP has been characterized as per NEHRP (National Earthquake Hazards Reduction Program) and IBC (International Building Code) site classification using an average shear wave velocity (Vs30) of 30m, obtained from MASW. In the study area, 58 one-dimensional (1-D) MASW survey has been carried out and respective velocity profiles are obtained. The major part of the BMP area can be classified as "site class D", and "site class C" and a smaller part in and around Lalbagh Park is classified as" site class B". Further site response has been carried out using measured shear wave velocity and synthetic ground motion developed by Sitharam and Anbazhagan [11]. Site response study shows that due to soil condition, large modification of wave amplitudes are observed resulting in higher peak ground acceleration when compared to rock level acceleration.

The NW-SE trending Zagros mountains form a linear belt more than 1500km in length, from eastern Turkey in the NW to the strait of Hormuz in the SE. They result from the continental collision between the Arabian plate and Central Iran that started during the Miocene [e.g. 40], or perhaps earlier in Cenozoic time. A threedimensional visco-elastic finite element model was developed in order to simulate long-term, displacement rate along the Main Recent Fault and Kazeun fault by adjusting the effective fault friction. In order to undertake this process, a friction range of 0.02-0.3 was used for a fault. A model was constructed using spatially varying crustal thickness, geothermal gradient, and two major faults. The mesh covers a rectangular area in the Zagros with horizontal dimensions of 1500km×600km and a depth extent of 70km. Structural boundaries are derived from several deep seismic soundings carried out in the area. The constructed model is first used in the calculation of thermal initial condition and secondly in analyzing the deformation. The structure of the fault zones is represented by contact surface with the Coulomb friction law. One of the most striking results of our rheological test is that the faults are locked if the friction exceeds 0.2. By comparing our results with geodetic measurements [48, 51], a realistic model is defined in which the displacement rates on the MRF and Dena, Kazerun and Borazjan faults reach 3.3mmyr-1, 2.8mmyr-1, 1.9mmyr-1, 0.5mmyr-1 for a fault friction of 0.02. These results strongly suggest that MRF and Kazerun fault are weak faults like San Andreas and North Anatolian faults

A GIS-based platform is developed by which shaking intensity and seismic landslide hazard zonation maps are generated in a short time after the earthquake. The shaking over the entire regional extent of earthquake prone area is obtained by Arias intensity attenuation relationship. By using simplified Newmark method, the seismic landslide hazard zonation map is generated based on the calculated Newmark''s displacements

According to most current building codes، in order to prevent a steel brace from brittle behavior due to buckling، it is necessary to use prescribed stronger and stiffer sections. However، experience from past earthquakes has shown that the above requirement is not effective in containing the brittle failure of members، not even in postponing this unwanted behavior. It is well known that one of the factors affecting dynamic behavior of a brace is its end condition، i. e. ، the stiffness of connection plates known as gusset plates (GP). In this paper through numerical simulation it is suggested to offset the connecting members at the connection to enhance the ductility and even strength of the connection itself. For the purpose of this research work، numerical models are studied using nonlinear static analysis. A very good match is shown to exist between results of computer simulation and experimental results، making it possible to study much more models at less time، effort، and cost، comparing to experimental work. A summary of results from numerical modeling and nonlinear analysis on 5 different connection configurations of cross and chevron bracing is also given and compared. It was shown that the eccentricity at connecting point is resulted in increasing ductility.

Site amplification in the Khorasan Seismic Network، Iran، was estimated using small earthquake events (ML 1. 6-5. 5) recorded from 2003 to 2006. This seismic network consists of 5 broad band stations (NJ، MH، BJ، QU and SB) distributed in Razavi and North Khorasan provinces. A total of 255 three-component waveforms from 88 events were used in this study. The wide dynamic range of the Guralp instrument provided a broadband seismogram for S-waves. Site effects were estimated by linear inversion using the reference site (NJ). The S-wave quality factor was found to be approximated by the relation 165f 0. 48 in the frequency range 0. 6-10Hz. It was found that the siteamplification factor for three kinds of geometrical spreading model R-1، R-0. 75، R-0. 5 was similar but the quality factor varied.