Insights to the Damaging Effects of August 7, 2020 (Mw 5.0) Mila Earthquake and Seismic Hazard Analysis of Northeast Algeria

Abstract

Here, we present a seismic hazard evaluation for the August 7, 2020 (Mw 5.0) Mila earthquake that occurred in northeast Algeria. The study addresses the environmental factors that could contribute significantly to the highly damaging impact of this event. The following aspects were included in an interdisciplinary methodology that was adopted: the earthquake catalog, the coseismic geologic impacts with respect to the Environmental Seismic Intensity (ESI) scale standards, and estimations of peak ground acceleration values based on both probabilistic and deterministic seismic hazard approach. A comprehensive study of main and secondary impacts was performed for three districts (El-Kherba, Grareme-Gouga, and Azzeba), to obtain a good seismic intensity assessment. A PSHA- and DSHA based hazard analysis for the region concluded that the unique intensity values were related to the Modified Mercalli Intensity (MMI) and PGA distributions. Our work shows that the considered hazard estimation processes can result in very diverse values of the PGA distributions. Furthermore, PGA values frequently deviate significantly from macroseismic intensity levels derived using the ESI scale. As a result, the combination of the environmental factors attached to the hazard assessments seems to be necessary to obtain an additional accurate seismic assessment. In the final phase, seismic hazard assessment methods were applied to obtain the estimated damage distributions at the risky locations for 50 years of exposure time. The results show the importance of taking precautions to reduce earthquake casualties in vulnerable old urban centers. This work proposes a probable methodology for conducting site-specific hazard and vulnerability estimations to mitigate earthquake hazards and support risk reduction measures.