Seismic Investigation of Jan-Meda and Bole Area for Possible Implications of Site Classification
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Date
2024-06
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Addis Ababa University
Abstract
Evaluating the seismic vulnerability of a building requires a significant understanding of subsurface conditions. This study employed the Multichannel Analysis of Surface Waves (MASW) technique to characterize and classify two distinct sites within Addis Ababa. By analyzing the dispersion of active and passive seismic records acquired by the 24-channel Geode seismograph, a significant contrast in the average shear wave velocity of the 30-meter-thick overburden (Vs30) was observed between the sites compared. This contrast directly translated into contrasting site classifications according to Eurocode 8 (EC8) and the National Seismic Hazard Program (NSHP). The findings highlight the importance of site-specific investigations for seismic resilience. Bole Homes area, characterized by a lower VS30 of 354.8 m/s, necessitates stricter foundation design and seismic mitigation strategies compared to Jan-Meda, where we managed to obtain a VS30 of 1304.7 m/s. The topmost layer of the Jan-Meda area seems to be dominated by volcanic rocks while velocity decreases at depth, and a clear discontinuity is visible at 50 meters depth, which needs further investigation. This research demonstrates the effectiveness of MASW in differentiating subsurface conditions and informing assisting site classification efforts. The resulting classification framework can guide construction practices, land-use planning, and targeted seismic risk mitigation efforts, ultimately fostering the development of earthquake-resistant building structure in Addis Ababa.
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Keywords
Shear Wave Velocity, Site Classification, Addis Ababa, Seismic Investigation, Multichannel Analysis of Surface Waves