Journal of Seismology and Earthquake Engineering
Volume:2 Issue: 3, Summer 2000

The generalized linear inverse technique has been applied to the problem of determining earthquake source models for five moderately large earthquakes in the Zagros Fold Thrust Belt (ZFTB). These earthquakes occurred in the southeastern (29 April 1987, m b =5.9, 12 July 1983, m b =5.8), central (12 July 1986, m b =5.6), northwestern (28 May 1983, m b =5.1, 18 December 1980, m b =5.8) parts of the ZFTB. Propagation and instrumental effects are deconvolved from the long period P and SH wave records of GDSN stations to obtain the teleseismic source time function using a damped least squares inversion. The inversion has the additional constraint that the source time function is positive everywhere. A comparison of source time function of these events show that the average source duration of earthquake along the strike-slip Kazerun fault is greater than the other parts of the region. Generally slow earthquakes have long source duration. Slow risetime presumably results from a very low stress drop. Focal mechanisms of the earthquakes are thrust in the southeastern ZFTB,and have strike-slip components in the central and northwestern ZFTB. Depth values of these events are estimated to vary between 5-15km. Considering the depths and observed emergent moment release, we speculate that these events occurred beneath the sedimentary sections near to the detachment horizon. The slip vectors along the Zagros zone that are computed on the basis of compiled focal mechanism solutions in this and previous studies show a similarity with direction of convergence between the Arabian plate and the Iranian plateau.

The Direct Boundary Integral Equation Method (DBIEM) studies the two-dimensional "in-plane" steady-state wave propagation problem in a non-elastic multi-layered region with non-parallel boundaries. Wave attenuation and dispersion due to the non-elastic soil behavior are investigated by the generalized Maxwell-Gurevich model (GMG model). The numerical example solved considers two real geological situations for a multi-layered soil media with existence of salt ore deposits. These situations concern one and the same geological region but in different periods of its exploitation in 1951 and 1994. There is a change of the situation during the years when the exploitation of the salt ore deposits has been done. The region is subjected to incident time-harmonic seismic P-waves. Theoretical amplitude-frequency characteristics at the free-surface points for elastic and non- elastic cases are obtained and compared.

The Pushover procedure is extended for seismic damage assessment of asymmetrical buildings. By mean of an example, it is shown that the accuracy of the proposed 3-D pushover analysis is similar to those applied to planar structures. The procedure is found to be more successful in estimating the global response parameters such as interstorey drifts than local damage indicators such as beam or column ductility demands

With the knowledge of constant threat of major earthquakes and expecially the latest dramatic and catastrophic earthquake of northern Iran in 1990 and recent quakes of 1997,a multi-disciplin- ary program was launched in Iran to assess seismic vulnerability of important buildings and possibly offer cost-effective strengthening solutions for the ones in need. As a result of the latest awakening toward upgrading the existing buildings in the country, especially capital city of Tehran, this papaer will concentrate on the upgrade design of a ten story steel framed hospital for both vertical and lateral loads, providing information on the strengthening procedures and considerations used to achieve the goals of the project. The existing structure under investigation is a ten story steel framed skeleton with four story completed and under use, constructed to old seismic code in 1985 and left alone due to economical reasons until 1997 the beginning of this project. Four different schemes were considered for this particular building which will be discussed herein with main considerations being economical and easy construction. Static equivalent procedure was utilized in the design of the upgrade system and then, behavior and design was controlled using non-linear dynamic analysis utilizing DRAIN-2D program. Details of this project will be discussed in this paper.

A computation and experimental study of dam-water-foundation interaction conducted at Longyangxia Dam in China is described. In the primary tests, the dam and its retained water were excited by detonating large explosive charges in shallow water upstream from the dam. The dam and water responses to the explosives were recorded by accelerometers, pressure sensors, and three-component seismographs. In secondary tests, the average reflection coefficient of the reservoir boundaries was measured using a newly developed procedure based on the acoustic reverberation concept. The results obtained indicate that explosive detonations appear to be the best means for exciting the dam-water-foundation system, and that an acoustic reverberation technique offers a practical procedure for measuring the overall reflection coefficient for the entire reservoir. Dam displacement and acceleration responses and hydrodynamic pressures due to acceleration signals recorded at the base of the dam were computed using current analytical procedures. Generally, reasonable agreement between the measured and computed responses was obtained but the prediction could be improved if non-uniform input motion could be defined and used.