Journal of Seismology and Earthquake Engineering
Volume:14 Issue: 1, Spring 2012

In this paper, we introduce a new approach to prepare the forecasting of earthquakes with magnitudes higher than a threshold level. This method can recognize the world''s dual seismicity zones, where an earthquake in one zone acts as a precursor to other events in some other zone(s). To do so, we first, divide the entire global plane into well-defined sub-regions, and then create a matrix whose different cells correspond to different spatial-temporal seismic attitudes. In this matrix, each cell identifies the total number of events occurred in that sub-region within that specified period of time. The method, then proposes a procedure to measure the possibility or likelihood of an event in those regions by looking through the current situation of the reference region. On the other hand, the method can forecast future status of the reference region by searching the database of earthquakes, which have occurred already, and this would further result in prediction of other double seismicity regions. Validity of the new forecasting approach is confirmed by the last year''s events data recorded in NEIC catalogue.

Probabilistic seismic hazard assessment (PSHA) of horizontal peak ground acceleration (PGA) and Uniform Hazard Spectra (UHS) on bedrock for different hazard levels is conducted in this study for Bojnurd city, the capital ofNorth Khorasan province, Iran. Therefore, all historical and instrumental earthquakes in a radius of 200 km of the center of Bojnurd city are gathered and after elimination of the aftershocks and foreshocks, the main earthquakes are identified in order to calculate the seismic parameters byKijko (2000)method. The seismotectonic model of the considered region and the seismic sources of the region have been modeled. Bojnurd city and its vicinity are meshed by 8 vertical and 11 horizontal lines. PGAs and UHS are calculated for all 88 points of the mesh using the logic tree method and different attenuation relationships with different weighted coefficients. These calculations are performed for two hazard levels of 10% and 2% probability of being exceeded in 50 years (hazard levels 1 and 2 respectively). Regional seismic hazard maps for PGAs andUHS for different locations ofBojnurd city and its vicinity are provided.

Response of underground structures exposed to seismic loading is a concern for designers, especially in large span opening. Siah Bisheh is one of the largest power plant projects in Iran that has three main caverns and is located in Alborz seismo-tectonic region, with high risk of seismic events. Seismic response of these caverns is considered in this study. For this purpose, the result of a robabilistic seismic hazard analysis that has been conducted in this region is used to determine the maximum design earthquake in the studied site. Numerical analyses are performed in three different media: continuum, semi-continuum and discontinuum media using two different software. PHASE2 V.5 software was used for modeling of the first and the second media, while UDEC software was applied for the third media simulation. The obtained results show that the discontinuum modeling, as compared to the continuum modeling, exhibits a good agreement with monitoring data in the static modeling. Furthermore, the wall between the Guard Gate cavern and the Power House cavern would be in the risk of instability.

This paper aims to ponder the effect of fuzzy uncertainties on performance evaluation of steel moment frame structures. Since the performance evaluation of a structure depends on its seismic demand and capacity spectra, any uncertainties in these two spectra causes uncertainty in performance level and performance point. Among many sources of uncertainties in structural dynamic analysis, in this paper, the modulus of elasticity, gravity load on the structure, dynamic properties of structure and soil properties have been considered and treated as fuzzy variables. To investigate the effect of these uncertainties, first, a nonlinear static pushover analysis program was written in MATLAB medium. Then, fuzzy inference model was used for determination of the design spectrum for different kinds of soils and seismic zones. The Effects of fuzzy uncertainties on capacity curve and capacity spectrum have been investigated on a typical example based on a new fuzzy concept in construction of the capacity spectrum of structures. Finally, performance point and performance level of structure has been determined as a fuzzy output.

The novel scaled boundary finite-element method is a fundamental solution-less boundary-element method based on finite element technology, which combines the advantages of finite-element and boundary element methods. Only the boundary is discretized reducing the special discritization by one as in the boundary element method; no fundamental solution is required as in the finite-element method; and the radiation condition at the infinity is rigorously satisfied. Making use of ascaling center the geometry of the problems is transformed into the scaled boundary coordinates including radial and circumferential coordinates. The boundary of the problem represents the computational domain. The finite-element approximation on the circumferential coordinates leads to the analytical equation in the radial coordinate.It is the goal of this paper to employ the method for soil-structure interaction analysis under seismic loads. The formulation of the method for seismic loadings is detailed for both bounded and unbounded problems. The structure is coupled with the unbounded domain on soil-structure interface. To demonstrate the applicability, simplicity and accuracy of the method, numerical examples modelled with the scaled boundary finite-element method are addressed. The results are compared with the results obtained from the commercial finite-element software SAP. Good agreement is achieved.

The Earthquake of 2005 in Pakistan destroyed more than 600,000 houses in the area covering 30,000 square km, equal to the size of New Zealand. Most of the houses were located in the rural areas i.e. on the mountains or inside the deep mountainous valleys. However, the three major urban settlements in the area, the towns ofBalakot, Muzafferabad and Bagh were badly affected. The ill-fated town of Balakot with estimated population of 37,000 was destroyed completely. 5000 people died and 95% of the infrastructure facilities were demolished. Later, the national and international consortium of specialists confirmed that the town is located on two major fault lines, running parallel all along the town. It was also confirmed that the epicenter of the 2005 Earthquake in Pakistan was 10 kmdeep beneath the town of Balakot. Interestingly, originating from central Asia region, the fault line enters Pakistan fromthe North West and pass through the towns of Balakot, Muzaffarabad and Bagh, then continues into Hindustan (India). To provide safe living environments for the affected towns, Urban Strategy was formulated by the Earthquake Reconstruction and Rehabilitation Authority. Transitional Housing Project and City Improvement Plan also became parts of the Urban Strategy to provide a reasonable, reliable and decent residential solution. In this paper, the interventions and strategies prepared and implemented to rehabilitate and reconstruct the town of Balakot and its peripheral areas after the devastating earthquake of 2005 is highlighted.