Abstract
A hazard assessment of the 1976 Guatemala earthquake (M = 7.5) was conducted to achieve a better definition of the seismic hazard. The assessment was based on the environmental effects that had effectively contributed to the high destructive impact of that event. An interdisciplinary approach was adopted by integrating: (1) historical data; (2) co-seismic geological effects in terms of Environmental Seismic Intensity (ESI) scale intensity values; and (3) ground shaking data estimated by a probabilistic/deterministic approach. A detailed analysis of primary and secondary effects was conducted for a set of 24 localities, to obtain a better evaluation of seismic intensity. The new intensity values were compared with the Modified Mercalli Intensity (MMI) and Peak Ground Acceleration (PGA) distribution estimated using a probabilistic/deterministic hazard analysis approach for the target area. Our results are evidence that the probabilistic/deterministic hazard analysis procedures may result in very different indications on the PGA distributions. Moreover, PGA values often display significant discrepancy from the macroseismic intensity values calculated with the ESI scale. Therefore, the incorporation of the environmental earth effects into the probabilistic/deterministic hazard analysis appears to be mandatory in order to achieve a more accurate seismic estimation.
Highlights
The last decade has witnessed the development of a novel generation of attenuation models [1], accompanied by a significant progress of computation possibilities, implemented GIS software, and the introduction of a new Environmental Seismic Intensity (ESI) scale [2,3]
The new intensity values were compared with the Modified Mercalli Intensity (MMI) and Peak Ground Acceleration (PGA) distribution estimated using a probabilistic/deterministic hazard analysis approach for the target area
The maximum intensity value of the ESI scale was attributed to Cabanas, Chuarrancho, El Progreso, Gualan, Quebradas, and Subinal cities, where the damage and the ground effects were extremely intense and could be appropriately described by XI-ESI degree
Summary
The last decade has witnessed the development of a novel generation of attenuation models (ground motion prediction relations) [1], accompanied by a significant progress of computation possibilities, implemented GIS software, and the introduction of a new Environmental Seismic Intensity (ESI) scale [2,3]. Recent research focused on hazard characterization has emphasized the importance of revaluating historical seismic events to improve our ability in developing reliable mitigation strategies [3]. These multidisciplinary approaches have found an ideal application in the case of the Guatemala region, one of the most active seismic zones of Central America. Several strong earthquakes hit the country with dramatic consequences. These earthquakes were mostly associated with devastating environmental phenomena that caused permanent changes in the landscape [4,5,6]. Even as destruction was severe both in terms of numbers of dead/injured and geographical extension, the maximum estimated intensity was IX Modified Mercalli
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