Major Minor Earthquake Felt in South Lebanon & Beirut

A recent underwater survey revealed that Lebanon lies dangerously close to a fault that could soon generate a catastrophic tsunami, according to a report by Discovery News channel. The fault, which according to the survey lies just four miles off Lebanon's coast, caused a tsunami-generating earthquake in 551 A.D. --Discovery

Lebanon is cut by faults of every scale. The longest fault in Lebanon is the Yammouneh Fault that runs along the western margin of the Bekaa and links the major fault of the Jordan Valley to the Ghab Valley Fault of Northern Syria. This is a lateral, or strike slip fault and is the Lebanese segment of the Dead Sea Transform Fault. It originated around 12 to 10 million years ago as the boundary between the Arabia Plate and the Levantine part of the African Plate and has ben moving since. The result of this is that the Bekaa has moved some 50 km northwards with respect to Mount Lebanon. The evidence suggests that the Yammouneh Fault has not moved for many thousands of years; and whether it is dead or dormant is not clear. We would dearly love to know will move again. Like many large faults the Yammouneh Fault is not actually very impressive on the ground and is often only marked by a wide breccia zone.

The Roum Fault, which runs from near Marjayoun towards Beirut is probably where most of the plate tectonic motion is going on now and may be the present plate boundary between the Arabian and the African Plate. One model is that the plate motion has fairly recently (in geological terms) switched from the Yammouneh to the Roum Fault. The last recent earthquakes in Lebanon have been along this fault including the Chhim earthquake of 1956 that caused many deaths and much damage. One slightly worrying point is that the Roum Fault seems to be on line for Beirut. If it does have an active fault segment near (or even under) the capital then that must raise the earthquake risk.

There are other major faults particularly in the Anti-Lebanon. The main highway to Damascus shows a good deal of faulting in the road cuts as it passes through this area. The Serghaya Fault in particular is apparently another major strike slip fault.

There many other faults in Lebanon with displacements ranging from a few centimetres to several kilometres. Working out which are major faults, and which are minor, is not easy. --AUB

USGS Report

Magnitude 5.0

Date-Time Friday, February 15, 2008 at 10:36:19 UTC

Location
33.377°N, 35.317°E

Depth
10 km (6.2 miles) set by location program

Region
LEBANON - SYRIA REGION

Distances
16 km (10 miles) NE (42°) from Tyre, Lebanon

57 km (35 miles) SSW (197°) from BEIRUT, Lebanon

70 km (43 miles) NNE (26°) from Haifa, Israel

Parameters
Nst= 32, Nph= 32, Dmin=615.5 km, Rmss=0.92 sec, Gp=104°,
M-type=body magnitude (Mb), Version=7