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LEBANON: Not All Earthquakes Are Political

Mona Alami

BEIRUT, Jul 11 2008 (IPS) - South Lebanon is reputed for orange groves and orchards lined with lush banana trees. For many around the world, it also conjures up images of a fierce battleground, where all regional conflicts come to life. In recent months, however, the region has also become known for its intense seismic activity.

More than 500 quakes have shaken Lebanon since Feb. 12, when a magnitude five earthquake shook the southern village Srifa to its core, creating panic among the population. “We are hearing weird sounds rising from the earth every morning, like a deep echo that is immediately followed by a quake. This usually occurs daily at dawn, when the sun starts to rise,” says Srifa’s mayor, Ali Eid.

People’s fears are mounting with each tremor, especially since Israel’s warning Jun. 30 that a massive earthquake may soon strike Lebanon.

“Lebanon is cut by faults, many of which stem from Yamouneh, the Lebanese section of the Dead Sea Transform Fault that extends from Jordan to Turkey,” says Dr Maya el-Kibbi, geologist at the American University of Beirut. Lebanon lies at the boundary between the Arabian Plate and the African Plate.

Many other earth faults also exist in Lebanon. The Roum Fault extends from the picturesque southern village Marjayoun towards capital Beirut, while the Serghaya Fault is a major strike slip fault. According to el-Kibbi, however, it is the Sour Zrariyeh Fault in the south that is believed to be causing much of the seismic activity in Srifa. A fault is an extended break in a body of subterranean rock, marked by displacement and discontinuity on either side.

The Lebanon area has witnessed several earthquakes, some of which completely destroyed the place. “The 551 AD seven magnitude earthquake caused a tsunami and a great deal of destruction, mostly in the coastal cities, especially around the Batroun area (in the north),” el-Kibbi says. The quake resulted from an offshore fault a few miles from Lebanon’s shores. Lebanon was subsequently hit by major earthquakes in 1170, 1202, 1759, 1837 and 1956. The years 1983 and 1997 saw significant seismic activity coming from various faults.

“The tremors we are currently experiencing are all occurring around the Sour Zrariyeh fault, which is relatively small in size. The actual size of the fault is a reassuring factor, as the intensity of an earthquake is usually proportional to the size of the fault involved,” says el-Kibbi. In this particular case, such a fault may not generate a more than six magnitude quake, which is considered of medium intensity.

The seismologist says tremors and quakes either herald larger seismologic activity or indicate that the earth is progressively diffusing energy. “We can’t predict, however, which of the two occurrences may be taking place,” she adds.

Earthquakes can occur wherever there is sufficient stored elastic strain energy to drive fractures along a fault plane. Most boundaries do have such asperities, and this leads to a storing of energy. When the stress has risen sufficiently, it breaks through the irregularity, releasing the stored energy and causing an earthquake.

“Even in the event of a medium size earthquake of magnitude six, there should be no casualties if constructions are properly built,” says el-Kibbi. In the South, however, most buildings have been erected haphazardly by the local population, often without the assistance of an architect, and without conforming to seismic building requirements. In addition, many constructions have been weakened by the intense bombing during the 2006 Hezbollah-Israeli war.

The Feb. 12 earthquake further shook the foundation of buildings in Srifa, cracking walls and ceilings, and forcing many in the village to flee their homes and live in tents. “Some 20 families whose houses have been significantly damaged are currently living in the fields,” says Eid.

El-Kibbi advises that building foundations should be carefully inspected and possibly reinforced before inhabitants return to their homes in order to prevent casualties in case a medium size earthquake occurs. In the meantime, many of Srifa’s villagers are playing it safe, forgoing the shelter of walls and taking refuge under the stars.