Issues in Seismic Zoning and Proposed Reconsiderations in Seismic Building Codes in Ethiopia

Issues in Seismic Zoning and Proposed Reconsiderations

in Seismic Building Codes in Ethiopia

University of California - Irvine

Henri Samueli School of Engineering

ICCEMCE-03, International Conference on Earthquake Engineering, Computational Mechanics, Geotechnical and Transportation Engineering

Addis Ababa, Ethiopia - January 9-10, 2003.

Due to its location right on one of the major tectonic plates in the world, i.e., the African and Arabian plates, earthquakes have been a fact of life in Ethiopia for a very long time [1]. In the 20th century alone, a study done by Pierre Gouin [2] suggests that as many as 15,000 tremors, strong enough to be felt by humans, had occurred in Ethiopia proper and the Horn of Africa. A similar study by Fekadu Kebede [3] indicated that there were a total of 16 recorded earthquakes of magnitude 6.5 and higher in some of Ethiopia's seismic active areas in the 20^th century alone. Further, according to a report published in 1999 [4], a 6.5 magnitude earthquake, which seismologist say could happen in areas of close proximity to Addis Ababa, could cause as many as 4000-5000 deaths, 8000-10,000 injuries and a displacement of as many as 500,000 people and a total damage in excess of 12 Billion Birr [$1.5 billion]. Therefore, earthquakes pose a clear and credible hazard in some of the most populated regions of Ethiopia.

This paper investigates the seismic zoning issues in the country that have a bearing on the magnitude of lateral earthquake loads that need to be used for the design of structures. In addition, a number of proposed reconsiderations on the EBCS-8 1995 are forwarded with the view of making the country’s current seismic code adequately conservative. Particular emphasis is placed on lessons learnt in the adoption of some pertinent international seismic codes.

References

1. Kassegne, Samuel, “Earthquake Risks in Addis Ababa and other Major Ethiopian Cities - Will the Country be Caught Off-guarded?”, http://www.mediaethiopia.com/Engineering/EarthquakeHazard_ET.htm, MediaETHIOPIA Website Feature Story, March 2002.

2. Gouin, Pierre, Earthquake History of Ethiopia and the Horn of Africa, International Development Research Center, Ottawa, Canada, IDRC- 118e, 259p, 1979.

3. Fekadu Kebede, Seismic Hazard Assessment for the Horn of Africa, Zede, Journal of Ethiopian Engineers and Architects, Addis Ababa, Ethiopia, 1996.

4. IDNDR RADIUS Project, Addis Ababa Case Study, Final Report. Prepared by Addis Ababa RADIUS group, et al, September 1999.