"Earth-shattering” events are relatively par for the course in Lebanon, with war, political upheaval and any number of social revolts rarely outside the realm of possibility at any given moment. The Lebanese, however, tend to focus on surface-level events to “rock” the nation, while few realize that below the ground they walk, an actual shattering of the earth is mounting.
“The possibility of a damaging earthquake happening in Lebanon is very high, and it is getting higher every day and every year,” said Ata Elias, assistant professor at the department of geology at the American University of Beirut (AUB), adding that the country could be hit with a quake reaching a magnitude of 7.5 on the Richter scale.
Lebanon stands on several major fault lines, which are cracks in the earth’s crust. Fault lines are at the boundaries between the earth’s tectonic plates and may range from less than a centimeter to several hundred kilometers in length. Tension can build along fault lines as the tectonic plates rub against each other, and if too much pressure builds the plates may shift, causing an earthquake.
The largest in Lebanon is the Yamouni fault that runs the length of the western Bekaa Valley, linking the Jordan Valley fault line to the Ghab Valley fault line in Northern Syria.
The Yamouni fault caused a major earthquake in 1202 A.D., and has a recurrence time of 800 to 1000 years, said Elias. Do the math, and you realize that the next major quake is set to hit between the years 2000 and 2200.
Lebanon’s many faults
The Yamouni is not the only fault putting Lebanon at risk, as there is another running along the coast — the Mount Lebanon fault — that is believed to have caused the catastrophic earthquake of 551 A.D., accompanied by a tsunami that hit the eastern Mediterranean and devastated the cities and towns along the coast. That earthquake is estimated to have had a magnitude of 7.5 on the Richter scale and caused 30,000 casualties in Beirut alone. The Mount Lebanon fault has a recurrence time of 1,500 to 1,700 years, which means another quake in the near future should not come as a surprise to anyone.
“We are now at a very singular moment in our geological history where we have two faults that might produce an earthquake,” said Elias.
Jordan, Syria and Palestine are also subject to seismic hazards and therefore any seismic activity that might be generated from these areas could affect Lebanon as well.
There are no means to know when exactly the major earthquake might occur, but that is not the sole issue since many smaller earthquakes are continuously taking place in Lebanon, such as the tremors witnessed in the south in February 2008, or the 5.3 magnitude earthquake that trembled Beirut in 1997.
The seismic hazard that Lebanon is subject to cannot be avoided, but the risk associated with the earthquake can be largely reduced by building safer structures and complying with seismic building codes.
Mohamed Hrajili, professor of civil engineering at AUB, said that it is very hard to calculate how many buildings in Beirut are built in compliance with seismic building codes, but gave an estimate of around only 20 percent.
Hrajili added that the most vulnerable buildings are those between 8 and 15 stories high, due to the frequency with which the ground would shake as well as other technical factors that characterize earthquakes in Lebanon.
Even though the number of buildings resistant to earthquakes is very low, awareness on the issue started to rise in the early 1990’s when engineers started to adopt seismic building codes in their designs and a ministry decree was issued in that regard. Hence, many of the new buildings that were constructed after the Lebanese Civil War comply with some building code, whether American or European.
Heading off disaster
When the post-civil war reconstruction of Lebanon started, a team at AUB initiated a study identifying the seismic hazards that the country is subject to, and proposed a set of regulations for the construction and design of new buildings.
“We wrote a proposal to the directorate of urbanism saying that something should be done in this regard,” said Hrajili, who was involved in that study.
Lebanon was zoned under the 2B designation in the Uniform Building Code of the United States. In 1997 and 2005 respectively, decrees were issued and amended stating that new buildings should comply with the codes suggested in the decree or any other internationally recognized building code. Hrajili said the decree includes standards to meant to make buildings as safe as possible, and more importantly, to prevent them from collapsing.
“We can tolerate cracks in the buildings but we don’t want them to fall on peoples’ heads,” he said.
According to the decree, a report should be submitted to the order of engineers in that regard before obtaining a construction permit.
Although the decree was issued, the experts Executive spoke to said there is no strict supervision over the implementation of these codes.
“They ask for the file so they know the study is done, but they don’t have the means to check everything,” said Alexandre Richa, head of the department of construction and civil works at Apave, which runs technical oversight on construction sites to verify the solidity of structures and personal safety. Richa said there should be an implementation law that follows the decree, stating how inspection and control should be done.
Sami el-Khoury, director at the engineering company Rafic el-Khoury and Partners agreed with Richa, adding that even very experienced engineers might not be aware of the details that should be included in the structure, and that’s why a more thorough inspection should be carried out.
Cities at risk
In the event of an earthquake, high density areas are at higher risk, as buildings are closely lined up and will cause substantial damage and casualties if they collapse. These areas are in major cities like Beirut, Tripoli, Tyre, Jounieh and others. “I don’t worry about the Bekaa, for example, even though the fault passes there…the houses are remote and we can shelter these people more easily and save their lives,” said Hrajili.
Another high-risk factor for Beirut and other coastal cities and communities is the possibility of a tsunami occurring, should the earthquake originate along the Mount Lebanon fault line. However, Elias said that tsunamis on the coastal line will not be higher than six to seven meters, thus mainly affecting the ports, the airport, and factories that lie in these areas.
Another worry experts point to is the fact that many districts and cities in Lebanon are built on sandy soil that has a high water content. If an earthquake takes place, soil liquefaction might occur and cause buildings and other structures to sink. Among the areas most at risk of this are the southern suburbs of Beirut, Bourj Hammoud, Tripoli and Damour.
“There are measures that should be taken into account; in sandy areas you have to do a liquefaction analysis for the sand on which the structure is resting and that will give you an idea of how to reinforce the soil, so that you don’t have a sinking effect,” said Khoury.
Shoring up shaky infrastructure
Not only can new buildings be protected against earthquake hazards, but old structures can be reinforced to minimize the risks associated with tremors as well.
However, while holding new structures to building codes adds, on average, five percent to overall costs, reinforcing old buildings would be very costly, said Richa. “The cost may be equivalent to demolishing the building and rebuilding another one,” he said.
Still, there are some important structures that should be protected, as Hrajili explained, despite the high cost associated with it.
“Not every building should be repaired, but the most important ones like government owned buildings, hospitals, schools, ministries,” said Hrajili.
Better safe than sorry
Although architects and engineers in Lebanon have come a long way in terms of seismic awareness and building code implementation, there is still much to be done before Lebanon could be considered prepared for potential seismic hazards.
“The government must create more awareness, like wearing seatbelts…now 80 percent of the people in Lebanon are wearing seatbelts because of the large [awareness] campaign,” said Khoury. He added that it is better to follow a certain methodology, because the cost of negligence is too high if an earthquake occurs and the country remains unprepared.
Hrajili said the most important thing is to create stricter continuous supervision, in order to ensure that engineers actually comply with the building codes.
“We only respect the code when there is an earthquake, for 1 to 2 years we pay attention and then afterwards we forget,” he added.
Building codes should be upgraded in accordance with geological and architectural studies.
“Codes should always be improved…take the example of the last earthquake that happened in L’Aquila, in Italy,” he added. On April 6 2009, an earthquake with a magnitude of 5.8 on the Richter scale shook the city. More than 300 people were killed, more than 1,000 were injured and around 30,000 were left homeless.
Keep in mind that most structures in L’Aquila followed European building standards for protection against seismic hazards. The next earthquake in Lebanon will make painfully clear which of this country’s developers have been as scrupulous.