Keywords: Bam earthquakes, empirical Green's functions, Kostrov slip function, synthesized strong motion, genetic algorithm, source parameters.

The main objective of this article is to estimate the seismological source parameters of the Silakhor earthquake which occurred on 31st March 2006, in the southern part of Iran. There are several approaches for modeling earthquake strong motion; for example kinematic omega²-based methods such as those of Boore [1] and Atkinson [2] which the rupture process is modeled by postulating a slip function on a fault plane and then using the elastodynamic representation theorem to compute the motion.

The empirical Green's Function approach was used for simulating the main shock and a genetic algorithm (GA) was utilized for modifying the seismological source parameters. Hutchings [3] proposed simple kinematic rupture models relying on moment, fault geometry, hypocenter location, slip function, rupture velocity, and healing velocity and rise time. The method used for simulating time histories only requires that the number of small earthquakes used in the synthesis is such that the sum of their moments adds up to the moment of the large earthquake, which matches the low frequency of the observed seismograms. The high frequency is matched simply by using appropriate rupture parameters.

Only linear-soil-response is taken into account. However it is possible that non-linear effects had been occurred during the main earthquake [4]. One of the best class of methods to achieve a nearly optimal solution in problems dealing with uncertainty and many imprecise variables is known to be GAs. A GA is a computer simulation of natural evolutionary processes to solve search and optimization problems.

We simulated the 2005 Silakhor Earthquake M6.1 at the Chalanchulan station, where the main shock was recorded using the EGF approach. The GA technique was used for reducing the uncertainties inherently existing in seismological source parameters by comparing the estimated 5% elastic response spectra and those of the recorded data. The paper contains a description of the empirical Green's functions, the GA method and tectonic setting, after which the sources of uncertainties in synthetic methods are discussed. Then the Silakhor earthquake main shock is simulated at Chalanchulan station, and compared with the recorded data at the same station. The results are given and discussed in the paper.

1

D.M. Boore, "Stochastic simulation of high-frequency ground motions based on seismological models of the radiated spectra", Bull. Seism. Soc, Am., 73:1865-1894, 1983.

2

D.M. Boore, G. Atkinson, "Stochastic prediction of ground motion and spectral response parameters at hard-rock sites in eastern North America", Bull. Seism. Soc. Am., 73, 1865-1894, 1987.

3

L. Hutchings, "Prediction of strong ground motion for the 1989 Loma Prieta earthquake using empirical Green's functions", Bull. Seism. Soc. Am. 81, 88-121, 1991.

4

L. Hutchings, "Kinematic earthquake models and synthesized ground motion using empirical Green's functions", Bull. seism. Soc. Am., 84, 1028-50, 1994.

5

D.E., Goldberg, "Genetic Algorithms in Search, Optimization, and Machine Learning", Addison-Wesley, Reading MA, USA, 1989.

purchase the full-text of this paper (price £20)

go to the previous paper
go to the next paper
return to the table of contents
return to the book description
purchase this book (price £145 +P&P)