Application of the Spatially Smoothed Seismicity and Monte Carlo Methods to Estimate the Seismic Hazard of Eritrea and the Surrounding Region |
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Authors: | L Hagos R Arvidsson R Roberts |
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Institution: | 1. Department of Earth Sciences, Uppsala University, Villav?gen 16, SE-752 36, Uppsala, Sweden
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Abstract: | The region of interest is characterized by incomplete data sets and little information about the tectonic features. Therefore,
two methodologies for estimating seismic hazard were used in order to elucidate the robustness of the results: the method
of spatially smoothed seismicity introduced by Frankel (1995) and later extended by Lapajne et al. (1997) and a Monte Carlo approach presented by Ebel and Kafka (1999). In the first method, fault-rupture oriented elliptical
Gaussian smoothing was performed to estimate future activity rates along the causative structures. Peak ground accelerations
were computed for a grid size of 15 km × 415 km assuming the centre of the grids as epicentres, from which the seismic hazard
map was produced. The attenuation relationship by Ambraseys et al. (1996) was found suitable for the region under study. PGA values for 10% probability of exceedence in 50 years (return period
of 475 years) were computed for each model and a combined seismic hazard map was produced by subjectively assigning weights
to each of these models. A worst-case map is also obtained by picking the highest value at each grid point from values of
the four hazard maps. The Monte Carlo method is used to estimate seismic hazard, for comparison to the results from our previous
approach. Results obtained from both methods are comparable except values in the first set of maps estimate greater hazard
in areas of low seismicity. Both maps indicate a higher hazard along the main tectonic features of the east African and Red
Sea rift systems. Within Eritrea, the highest PGA exceeded a value 25% of g, located north of Red Sea port of Massawa. In
areas around the capital, Asmara, PGA values exceed 10% of g. |
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Keywords: | spatially smoothed seismicity Monte Carlo methods seismic hazard peak ground acceleration Eritrea |
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