Journal of Seismology and Earthquake Engineering
Year:2009 | Volume:10 | Issue:4|Papers Count:7

This research investigated the S wave velocity structure below SE Asia, by analyzing the seismograms of South Sumatra earthquakes at CHTO, QIZ, KMI, ENH and SSE stations, in the time domain and three Cartesian components simultaneously.The main data is waveform comparison between the measured seismogram and synthetic one, instead of travel time or indirect data from dispersion curve, as other seismological researches. The synthetic seismogram constructed from anisotropic PREM global earth model deviates greatly from the measured one, from surface wave to multiple core reflected waves. Corrections cover the gradient change of bh in the upper mantle layers, which turns from negative into positive, as stated in the anisotropic PREM, changes of earth crust depth and zero order coefficients of b velocity function in all earth mantle layers. So the fitting is obtained on the arrival time, the Love and Rayleigh surface wave, the S, and the repetitive core reflected ScS, ScS2 and ScS3 waves. This result reveals that South East Asia, being stretched due to tectonic release, has a mantle part with negative anomaly on S wave velocity and vertical anisotropy in all earth mantle layers. Error in CMT solution is shown by distinct amplitude differences in the surface waves.

The modeling and analysis of structures subjected to earthquake loading are well studied and understood. During an earthquake, however, the behavior of the soil under the structure plays an important role in determining the superstructure response. In most cases, the soil is not modeled and is ignored. This is due to the reason that the soil, contrary to the structure, is an infinite domain and can not be treated with the conventional models as used in structures. Cone models to represent the soil, have been developed for practical engineering applications during the last ten years. Cone models can be utilized for sites with general layering and embedment conditions, capturing all degrees of freedom. Cone models provide sufficient engineering accuracy with physical insight. Cone models can be used both in force-based methods as response spectrum and time history analyses and in displacement-based methods such as push-over calculations. In these models, the soil is represented with a series of bars and beams as one uses in the analysis of superstructures. In this paper, the development of cone models is reviewed. Further, the application of the cone models in two actual seismic retrofitting projects is demonstrated. In both cases, the retrofitting costs were reduced substantially after modeling the soil with cones.

Vulnerability of urban fabrics to potential earthquakes is related to several parameters including seismic and geological hazards level, site effects, physical vulnerability, social and economical conditions and disaster management/ emergency response capacity. In order to evaluate the impacts of these parameters and estimate the integrated vulnerability at each urban fabric, it is essential to study their effects separately and then compile them by using appropriate methods and weighting factors. In this paper the seismic vulnerability of Tehran will be evaluated by considering some of the above-mentioned parameters and then the results will be compared with the existing plans and programs for rehabilitation of the old urban fabrics in Tehran prepared based on the laws and regulations of Ministry of Housing and Urban Development of Iran. The results show that the plans which are prepared merely based on physical vulnerability, can not properly identify the priorities for rehabilitation of urban fabrics in seismic prone zones and it is necessary to consider the impacts of earthquake related parameters as well as socio-economic conditions for improvement of vulnerable areas.

The validity of ASCE7-05 standard guidelines for considering the effects of vertical component of earthquake on the response of moment resistant steel buildings for use in Iranian code were re-evaluated. Three steel buildings and 9 near-fault recorded earthquake motions were considered. It was shown that both ASCE and 2800 standards overestimate the displacement of buildings and the vertical component of earthquake has no significant effect on the maximum displacement of stories. It has also been observed that using the ASCE equation for considering the vertical component of earthquake in far-fault areas can lead to an overestimation of axial force of columns, but in near-fault areas it can lead to a rather good estimation of axial force of columns. In light of this research, it can be found that loading patterns of Iranian code (with or without considering ASCE equation) can overestimate moment of columns and using the ASCE equation in Iranian code for near- fault analyses is recommended.