By Samuel Kinde
According to a report published in 1999, a 6.5 magnitude earthquake, which seismologist say could happen in areas of close proximity to Addis Ababa, the country’s major city, 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]. Addis Ababa itself is only 75-100 kilometers away from the western edge of the Main Ethiopian Rift Valley, which is a hotbed of tremors and active volcanoes. Some of Ethiopia’s major cities like Addis Ababa, Nazret, Dire Dawa and Awassa are very near main fault lines such as the Wonji fault, the Nazret fault, the Addis-Ambo-Ghedo fault, and the Fil Woha fault lines along which numerous earthquakes of varying magnitude have occurred over the years. Other cities like Arba Minch, Dessie, and Mekele are also located in some of the most seismically active areas in the country. The presence of the Fil Woha hot springs in the middle of Addis Ababa itself, for example, is nature’s reminder that the city lies on fault lines that have been slowly building strains. It is the release of these strains accumulated over the years that cause the phenomenon of earthquake.
Pierre Gouin, founder and long-time director of the Geophysical Observatory at the Addis Ababa University has extensively written about earthquake hazards in Ethiopia, particularly from the 1400’s to 1977 in his now classic book: Earthquake History of Ethiopia and the Horn of Africa [2]. In his book, Gouin describes the earthquakes of 1906 and 1961 that shook Addis Ababa and caused widespread panic. Gouin writes, “the magnitude of the main shock of 25 August 1906 was 6.75; the estimated epicentral location, 100 km south of Addis Ababa. The August tremors were exceptionally violent. It is also reported that the shock of 28 October was strong enough to cause the bells of the Church in the Finfine district to ring spontaneously.” He further adds, “The population of Addis Ababa was greatly afraid. Damage, however, was slight because: the town, being barely 10-years-old, had not yet fully developed.”
Kara Kore earthquake 1961(Photo: P. Gouin)
With regard to the effect of the 1961 Kara Kore-Majete earthquake on Addis Ababa, Gouin writes, “At Addis Ababa, some 200 km south of Kara Kore, the first earth tremors were felt at breakfast time on 19 May (1961); many others were felt off and on for at least 2 weeks. Their occurrence was followed by a wave of rustling noises generated by the twisting of the corrugated iron roofing sheets covering most houses. Some masonry structures cracked, partition walls in reinforced concrete frame buildings were dislocated by shearing motion, etc., especially along the Filowoha fault zone in the southern sector of the city. At Africa Hall, a 7-story building under construction but whose frame-structure was completed, the steel flagpoles on the roof were seen crisscrossing during the tremors.”
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. In the 20th century alone, a study done by Pierre Gouin 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 [2]. A similar study by Fekadu Kebede of the Ethiopian Geophysical Observatory at the Addis Ababa University published in 1996 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 20th century alone [3]. The most significant earthquakes of the 20th century like the 1906 Langano earthquake, the 1961 Kara Kore earthquake, the 1983 Wondo Genet earthquake, the 1985 Langano earthquake, the 1989 Dobi graben earthquake in central Afar, and the 1993 Nazret earthquake were all felt in Addis Ababa, and the other major cities of Nazret and Awassa.
So, from minor damages in the 1906 and 1961 earthquakes, what has brought us to a potential disaster that could claim the lives of as many as 5000-8000 people in Addis Ababa alone?
Majority of the Buildings in Ethiopia are at Risk
The past 50 or so years have witnessed a dramatic increase in urbanization in Ethiopia associated with increased population. This increase in the urban population has been accompanied by an equally strong growth in the number of high-rise buildings, residential houses, schools, bridges, water supply pipes, and other infrastructure constructions. Therefore, the proximity of these significant earthquakes to the major population centers such as Addis Ababa, Awassa and Nazret, obviously leads to the question of how much damage will be sustained by these buildings, bridges, dams, water supply pipes and other so-called life-lines. The majorities of buildings in these cities, as in many cities in developing countries, were not designed as per a strict earthquake design guidelines and could, unfortunately, sustain significant damage varying from total collapse to structural failure that will render them unfit for occupation. An increasing number of buildings, especially those built recently, do not even go through a proper quality control procedure to assure compliance with some basic requirements of the country’s building code standards. As a result, shabby constructions are increasingly becoming a common practice.
In general, the types of buildings that will be most affected are what engineers call “stiff” buildings such as stone and brick masonry buildings of all heights and reinforced concrete buildings with stiff infill and partition walls that have mushroomed in these cities over the past 15- 25 years. These “stiff” buildings do not have the required “ductility” and resilience to absorb and dissipate the massive amount of energy impacted on them by the earthquake loads.
Further, most stone and brick masonry buildings have extremely poor connections between the different components and under a significant earthquake load will simply crack and even fall part. The majority of these masonry buildings do not have steel reinforcement and when they do, the reinforcements were not detailed in accordance with earthquake-resistant design requirements. Concrete buildings, on the other hand, will experience, in addition to cracks and foundation failures, beam- column joints failures due to poor reinforcement detailing that could keep them as one unit.
“Interestingly enough, the mud and timber houses that most people in these cities live in are expected to fare much better due to their ‘ductility’ or elastic behavior under earthquake loads,” says Ato Samson Engeda, a senior structural engineer who was interviewed for this article.
Dr. Asrat Worku, Assistant Professor of Civil Engineering at the Addis Ababa University added, “The threat to human life due to damage of such structures is also expected to be not as severe as that of the failure of stiff structures”.
What will make matters worse is the fact that most hospital buildings in these cities, like the Black Lion Hospital, Menelik Hospital, St. Paul Hospital, Balcha Hospital, Ras Desta Damtew Hospital etc., will most probably experience serious structural damage and perhaps total failure themselves due to their non- ductile (non-elastic or stiff) behavior and lack of earthquake- resistant design. Menelik, Ras Desta Damtew and Balcha Hospitals for example are built of a heavy stone masonry with inadequate restraints that will likely collapse or sustain major structural damage under a 6.5 magnitude earthquake. In addition to the potential loss of life due to their collapse, a further loss is inevitable as these hospitals will be unable to function by taking in any patients that need immediate attention due to the earthquake hazard. School buildings in these cities, such as those of Black Lion, Medhane Alem, Addis Ketema, etc are also traditionally made of concrete and stone masonry which will experience severe damage and potential collapse under such a magnitude of earthquake.
To make matters worse, the soil conditions in certain areas of Addis Ababa, particularly areas like Fil Whoa, Mesqel Square, Bole, Beqlo Bet, Nifas Silk, Lideta, Mekanisa etc., actually may aggravate the effect of earthquakes. These areas consist of layers of soft soil deposits (as much as 15 meters deep in the case of the Fil Woha area) that further amplify the earthquake-induced ground motion. These amplifications of earthquake forces will, inevitably, lead to foundation and structural failures. Buildings and structures in these areas, are, therefore highly susceptible to more damage than their counter parts in areas like Intoto, Kolfe and Shola which have a thick layer of basalt rock nearer to the surface. The failure of industrial structures that process chemicals, and petroleum products in the mainly industrial area of Nifas Silk on the main road to Debre Zeit could be catastrophic due to potential leakage of poisonous gases and chemicals. In fact, the danger from structural failure of these structures that house some of the country’s heavy industries is a threat that hasn’t been adequately discussed in public, as the RADIUS report correctly identified.
In addition, the country’s major outlet to the outside world, i.e., the Bole International Airport’s runways could potentially experience damage that will render them unusable, especially for larger aircrafts. Structural damage to the old and the new terminal could potentially be significant as well, since these buildings are not designed to resist such a magnitude earthquake and are built on deep layers of soil that could amplify ground motion. This will further complicate any rescue and relief efforts from outside.
| Location | Year | Magnitude | Distance of Epicenter from Addis (kms) ** | Damage |
| Langano | 1906 | 6.8 | 110 | Felt as far as Addis. |
| Kara Kore | 1961 | 6.7 | 150 | Town of Majete destroyed. Kara Kore seriously damaged. |
| Central Afar Area | 1969 | Town of Serdo destroyed. | ||
| Wendo Genet | 1983 | 300 | ||
| Langano | 1985 | 6.2 | 110 | |
| Rift Valley Area | 1987 | 6.2 | 200 | Widely felt and widely-spread damage. |
| Dobi [Central Afar] | 1989 | 6.3 | 200 | Several bridges damaged. |
| Nazret | 1993 | 6.0 (?) | < 100 | Injuries and damage in Nazret. Also felt in D. Zeit and Addis. |
| Lake Shala – Adamitulu | 1999 | 250 |
Table 1. Some of the recent significant earthquakes that have rocked the Rift Valley, the Afar Plains and the Western Edge of the Rift Valley. Sources [2], [3] and [6].
Bridges, Dams and Water Supply Networks are at Risk
Damage due to earthquakes is not, unfortunately, limited to buildings only. Bridges, which form one of these cities’ major lifelines, are susceptible to significant damage and total collapse. Most of the country’s major bridges consist of reinforced concrete decks and stone-masonry columns and abutments that are not ductile enough to resist any significant earthquake forces.
“Potential damages include abutment and column failures that will render hundreds of such bridges unusable further exacerbating the damage from an earthquake,” says Ato Kassaye Seyoum, a senior structural engineer.
“To make things worse, the most important roads that link the presently land-locked Ethiopia to the neighboring countries that provide access to the sea run either across or alongside the main rift valley-a hotbed of seismic activity,” added Dr. Asrat Worku, an Assistant Professor of Civil Engineering at the Addis Ababa University.
Further, the major dams in these areas, namely, Legedadi, Gefersa, Dire and Koka Dam (which is itself in the Main Ethiopian Rift Valley) are also susceptible to damage due to earthquake forces. The Legedadi Dam is built from concrete and rock fill, while Gefersa and Dire dams that supply water to Addis Ababa are made of stone masonry and earth respectively with no known earthquake-resistant design consideration. A damage to these dams not only means the disruption of clean water supply to the city of Addis Ababa but also a potential flooding of nearby low- lying areas that is inhabited by people. The majority of pipelines that carry water from these dams to Addis Ababa and the numerous concrete reservoirs located in various parts of the city could also potentially experience damage. Similarly, the potential damage or failure of Koka Dam could result in flooding and loss of human life along with the disruption of electricity supply to the majority of the country. The economic consequences of such disruptions alone could be monumental.
State of Engineering in Ethiopia
Given the devastating effect earthquakes in the areas not far from these cities potentially carry, the obvious question that comes to mind is: How did engineers, owners, and government bodies fail to see these potential disasters? To start with, over the years the country had experienced far worse natural and man-made disasters like drought and famine and war that have made other potential disasters like earthquakes and forest fire be perceived as less likely and, perhaps, less- devastating. Further, most of the seismic prone areas started being populated only recently and there hasn’t been any precedence of a large-scale earthquake hazard in the country in the past 30-50 years that forces people to consider earthquakes as one of the natural disasters that have wrecked havoc in the country. The additional expense of earthquake-resistant design is also a major factor that has prevented many building owners from seriously considering its adoption. The economy issue associated with earthquake-proof design will remain a major obstacle to future adoption of a strict code of standards for earthquake-resistant design.
Even though, the country adopted its first earthquake design code of standards in 1983 [4], traditionally, building officials in the country have never made seismic-resistant code implementation neither a priority nor a necessity. Economic conditions, it can be argued, will make implementation an expensive proposition. However, this is a shortsighted argument as repairing potential damages from earthquakes could easily be much more expensive, if at all possible with the country’s meagre sources. The good news, on the other hand, is that as more studies predict the magnitude of potential earthquakes and their possible devastating effects on the country’s major urban centers, there seems to be a growing concern and awareness about the danger of earthquake hazards. The formal adoption of a detailed building code of standards for earthquake-resistant design in 1995 is by itself an encouraging development [5]. Its adoption, however, seven years from its date of formal publishing is yet to be realized.
“It is important to note that seismic provisions in code standards of countries having earthquake-prone regions are updated at least once or twice in such a span of time (i.e., 7 years),” commented Dr. Asrat Worku of AAU.
It is interesting to note that Ethiopian building officials and engineers can learn a lot from their counter-parts in other parts of the world like India, Greece, Turkey and Taiwan that experienced devastating earthquakes in the past 5 years. All these countries, like Ethiopia, do have strict seismic codes of standard but were not able to implement them well due to various reasons varying from poor quality-control and poor enforcement to inadequate or no construction supervision. More interestingly, the low to mid-rise reinforced concrete buildings that have mushroomed in Ethiopia’s major cities over the past 20 years or so share very identical design and construction characteristics with their counter-parts in these countries. As seen in the August 17, 1999 earthquake of Istanbul, the September 7, 1999 earthquake in Athens, the September 21, 1999 earthquake in Taiwan, and the January 21, 2001 earthquake in Gujarat, India, such buildings that consist of poorly designed reinforced concrete farmes with un-reinforced masonry infills experience severe damage resulting in loss of life. Ethiopian building officials, engineers and architects, therefore, should take note of the probable fate of these builings in the country’s major cities in the event of an earthquake. Further, as they are the professionals ultimately responsible for the design and construction of buildings and bridges, government building officials, engineers, architects and professional engineering organizations such as the Ethiopian Association of Civil Engineers (EACE), Ethiopian Association of Architects (EAA), Ethiopian Association of Seismology and Earthquake Engineers (EASEE), and the Ethiopian Association of Consulting Engineers and Architects (EACEA) have the professional responsibility to call for and implement a rational earthquake-resistant building, bridge and lifeline design in the country.
What Needs to be Done?
With the continuing realization of the potential risks of earthquake hazards to the country’s major urban centers, discussion on preventive as well as retrofitting measures along with contingency plans has already begun in the country even though there is no clear guidance if the momentum could be kept and the country’s pertinent professionals are involved. The outcome of the RADIUS project of 1999, for instance, is the right step in the right direction.
From pre-disaster planning point of view, the following action items are proposed:
1. Implement aggressive enforcement of the country’s building code standard requirements for newer buildings.
2. Improve quality control procedures in construction of new buildings.
3. Start sustained retrofitting effort on some of the key hospital and school buildings. Particular emphasis should be placed on industrial structures in the Nifas Silk area that house heavy chemical and petroleum-product factories. The retrofitting work recently completed on the privately owned Selam Hospital in the Mekanisa area can serve as a good example.
4. Implement retrofitting of major lifelines like water pipelines and electrical sub-stations. The major dams also need to be strengthened.
5. Provide incentives such as low-interest rate loans to owners of buildings to finance retrofitting projects.
From “during and post” disaster contingency plan point-of-view, the following recommendations should be adopted for the desired results:
1. Prepare mobile bridges to be used in key locations.
2. Provide emergency water supply, and emergency maintenance of water pipelines.
3. Provide stand-by tents to house emergency medical units
4. Provide stand-by emergency generators and mobile sub-stations.
5. Provide alternate emergency airfields.
Financing these measures is of course a huge undertaking that the country simply can not afford from its own sources. International aid is the only plausible source of financing that should be pursued by the government. International aid for financing retrofitting projects, of course, will not be delivered to the country unless it asks for it. Mouroux Pierre, one of the RADIUS project participants who was interviwed for this article echoed the same sentiment by saying, “as I could realize it in 2000 (One year after the end of RADIUS), the problem is political, because any interesting large projects for this mitigation must be proposed directly by the Ethiopian Government or the Mayor of Addis himself, in order that they can funded by any (World, European or French) Institutions.”
Conclusion
Given the fact that earthquakes are a fact of life in our part of the world and that the country’s major cities are subjected to a credible threat of significant ground shakings, it is impossible to ignore the potential loss of life and massive damage that the country could face. Also, given the rather poor state of the country’s economic condition, it is perhaps reasonable to assume that the country, by its own, will not have enough resources to rebuild damaged buildings, dams, bridges, water pipes, transmission lines and other life lines in a reasonable span of time. This will further erode the already poor living standards of its citizenry. Therefore, before these credible and highly probable natural disasters are realized, it is imperative that all major stakeholders including the various levels of government should prepare a contingency plan on how to face such disasters and further realize that more potential damage could be prevented by starting to enforce the strict building design codes of practice already in place. The role of engineers, architects and contractors and professional organizations such as EACE, EASEE and EACEAA in facing this challenge and educating the public about earthquake hazards is critical.
Notes:
** In a private communication, Dr. Laikemariam Asfaw, the director of the Geophysical Observatory at AAU suggested that the direct distances of the epicenters of some of the earthquakes given in Table 1 from Addis Ababa may actually be considerably shorter.
References
1. IDNDR RADIUS Project, Addis Ababa Case Study, Final Report. Prepared by Addis Ababa RADIUS group, et al, September 1999.
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. ESCP- 1:1983, Ministry of Works and Housing, Addis Ababa, Ethiopia, 1983.
5. EBC5-8- 1995, Code of Standards for Seismic Loads, Ministry of Works and Urban Development, Addis Ababa, Ethiopia, 1995.
6. Fekadu Kebede, Hazard Maps of Spectral Response Acceleration for Ethiopia, Proceedings of the Second Symposium of the Ethiopian Association of Seismology and Earthquake Engineering (EASEE), Addis Ababa, Ethiopia, April 4, 1997.
(This article was originally published on MediaEthiopia.com, March 2002. The author is a registered engineer in the State of California with experience in earthquake analysis and design of buildings.)