Probabilistic Seismic-Hazard Assessment for Eritrea

To date little is known about seismic hazard in Eritrea, despite its location in a volcanically and tectonically active region, and the gathering pace of major infrastructure projects. In response, we report the findings of a comprehensive probabilistic seismic-hazard assessment for Eritrea and adjacent areas. Seismic source and groundmotion models are constructed separately; we use an adaptive spatiotemporal smoothing method to map expected patterns of seismicity. To construct a consistent earthquake catalog from different data sets, we use orthogonal regression to convert and unify different magnitude scales. A sensitivity analysis of the different input parameters helps constrain them and disaggregation of site-specific hazard estimates yields insights into the relative contribution from seismic sources of different magnitudes and distances. The results highlight seismic hazard in proximity to the Red Sea, Gulf of Aden, Afar depression, and along the boundaries of the Danakil microplate. We estimate a 10% chance over 50 years of observing pseudospectral accelerations (PSAs) at 0.2 s exceeding 0:16g in the port city of Massawa (population similar to 32,000) and the town of Bada (population similar to 4000). For the capital, Asmara (population similar to 520,000), we calculate a PSA of 0: 11g at 0.2 s. Compared with previous studies, our results provide greater spatial resolution, use more recent ground-motion models, and benefit from a smoothed seismicity method. Our aims are to stimulate further studies and contribute to the safe development of the region in light of its exposure to seismic hazards.