Seismicity in the Afar Depression and Great Rift Valley, Ethiopia

Abstract

Integrated mapping is essential in geological studies to assess risks of earthquake hazards. Cartographic techniques have become a commonplace approach to visualizing data in the continuous geologic and geophysical fields. However, traditional GIS mapping is a manual process with a time-consuming workflow that can lead to mistakes and misinterpretation of data. This study applied two mapping approaches to address this problem: Generic Mapping Tools (GMT) used for automated cartographic workflow employing scripts and QGIS used for traditional geologic mapping. The study area includes Ethiopia, notable for its complex geologic setting. The study aimed to analyse the relationships between the geophysical, geological, topographic and seismic setting of the country by presenting six new thematic maps:
1 topography based on the GEBCO/SRTM15+ high-resolution grid;
2 geological units with consistent lithology and age from the USGS database;
3 geological provinces with major Amhara Plateau and Somali Province using USGS data;
4 geoid based on the Earth Gravitational Model 2008 (EGM-2008) grid;
5 free-air gravity anomaly model using satellite-based remote sensing data;
6 seismicity showing earthquakes and volcanos from 05/03/1990 to 27/11/2020.
The comparison of the topography, seismicity, geophysics and surface geology of the Afar Depression and the Great Rift Valley was based partly on extant literature on the geologic setting of Ethiopia which primarily focuses upon discussing tectonic processes that took place in the East African Rift System in the past. The current study contributes to the previous research and increases cartographic data on the geology and geophysics of Ethiopia. The outcomes can be implemented in similar regional projects in Ethiopia for geophysical and geological monitoring.