‫التقرير النهائي‬
‫عند انتهاء مشروع البحث يطلب من الباحث الرئيسي إعداد تقرير علمي موضوعي‬
‫يتضمن اآلتي‪:‬‬
‫‪ -1‬عنوان المشروع بالكامل باللغتين‪ ،‬كما ورد في نص وثيقة المشروع األساسية؛‬
‫‪ -2‬األهددداا التددي كانددة مر ددوش مددن المشددروع والن دواتر التددي كانددة مقددررش ومدددش البحددث كمددا‬
‫وردة في النص األساسي للمشروع؛ وما تحقق منها في نهاية المشروع؛‬
‫‪ -3‬الخطواة التي أن زة عملياً باختصار‪ ،‬ولكن بوضوح‪ ،‬مع اإلشارش إلى صعوباة وا هة‬
‫الباحث‪ ،‬إن و دة‪،‬‬
‫‪ -4‬قائم ددة ب دداألورام العلمي ددة الت ددي نش ددرة ف ددي الم د د ة اة الع ق ددة‪ ،‬و‪/‬أو الت ددي ق دددمة ف ددي‬
‫مؤتمراة علمية عالمية‬
‫‪ -5‬نس ددخة طب ددق األص ددل م ددن األورام المنش ددورش ف ددي م د د ة محكم ددة‪ ،‬كم ددا نش ددرة ف ددي تلد د‬
‫الم‬
‫ة‬
‫و بعددد إعددداد تقريددر نهددائي يتضددمن البنددود الم د كورش أع د ‪ ،‬يددت إيداعددا الم لددا بواسددطة‬
‫رئيا ال امعة‪ ،‬حيث أ ري البحث‪.‬‬
Administrative Information
‫المعلومات االدارية‬
Project Title - ‫عنوان المشروع‬
Implications of the Recent Discovery of Offshore Thrust fault System and Other SeismoTectonic Developments on the Seismic Hazard of Lebanon. (0-11-07)
Principal Investigator - ‫الباحث الرئيسي‬
‫رق الهاتف‬
‫العنوان االلكتروني‬
Telephone
e-mail
01-350000 mharajli@aub.edu.lb
(Ext. 3527)
‫العنوان‬
Address
Faculty of
Engineering
and
Architecture
- AUB
‫الوظيفية‬
Post
Professor
‫المؤسسة‬
Institution
AUB
‫االس‬
Name
Mohamed
Harajli
Co-Workers - ‫الباحثون المشاركون‬
‫العنوان االلكتروني‬
e-mail
Salah@aub.edu.lb
Two years
‫المؤسسة‬
Institution
AUB
‫االس‬
Name
Salah Sadek
: Duration -‫المدة التعاقدية للمشروع‬
Scientific Information
‫العلمية‬
‫المعلومات‬
ّ
Objectives - ‫الهدف‬
Objectives
Until recently, the main active faults within Lebanon were thought to be the Yammouneh,
Rachaya, Serghaya and Roum faults. Accordingly, all earlier studies of the seismic hazard of
Lebanon were based in part on this assumption. The recent mapping by SHALIMAR marine
geophysical campaign of a previously unknown, active thrust fault system – the Mount Lebanon
thrust (MLT) – calls for re-evaluation of the seismic hazard of Lebanon, particularly since the
newly mapped fault is located close to the coastal line where most of Lebanon’s population,
cities and capital investments are concentrated.
The objective of the current study is to update the seismic hazard of Lebanon, taking into
account the newly mapped fault system and associated geological and seismological findings,
and recently developed ground motion attenuation relationships appropriate to the region under
investigation.
Achievements -‫أالنجازات المحققة‬
Achievements
Proposed seismic zone parameter
At present it is common practice in Lebanon to design most structures with an intended lifespan
of 50 years for a PGA of 0.2g, which is quite plausible when considering the results of Model I
(Error! Reference source not found.) in which Lebanon is considered as one seismic area
source and any point within this area source has an equal probability of producing an
earthquake of any magnitude up till 7.5. However, Models II and III are more realistic,
considering that large earthquakes are most likely to occur along one of the major active faults.
Due to the uncertainty with respect to the activity of the faults as well as the adopted
attenuation equation, it is better to take the results of all models into account, including those
using the other two attenuation equations. In light of this study and the newly discovered
offshore tectonic feature, it is recommended to design for a PGA of 0.25g in the larger part of
Lebanon. However, for the coastal area between Saida and Tripoli, where most of Lebanon’s
population and capital investments are located, as well as for the area around the central part of
the Yammouneh fault, it is advisable to consider Model II and adopt a PGA of 0.3g.
The recommended ground accelerations above are the minimum that should be used in
seismic design and may be taken conservatively as the ground acceleration at the bedrock level.
The final design acceleration may be amplified depending on the type of soil overlying the
bedrock, and the dynamic characteristics of the structure. Classification of soils in Lebanon
with regard to their influence on the dynamic response under earthquake loading were covered
in detail elsewhere (Harajli et al. 1994).
Perspectives - ‫آفاق البحث‬
Perspectives
This study was undertaken to evaluate the implications of the newly mapped offshore thrust
fault system on the seismic hazard of Lebanon and the already established seismic zone
parameters used by the engineering community for earthquake design in Lebanon. This is
particularly critical since the fault is located at a close proximity to the major cities and
economic centers of the country. In line with earlier seismic hazard studies, the updated seismic
hazard was assessed using probabilistic methods of hazard analysis. The potential sources of
seismic activities that affect Lebanon were identified, taking into account the newly mapped
fault system, and the earthquake recurrence relationships of these sources were developed from
instrumental seismology data, historical records, and earlier studies undertaken to evaluate the
seismic hazard of neighboring countries. The sensitivity of the results to different assumptions
regarding the seismic sources in the Lebanese segment and the choice of the attenuation
relationship were evaluated. Maps of peak ground acceleration contours, based on 10 percent
probability of exceedance in 50 years, 100 years and 500 years time spans, were developed.
Publications & Communications - ‫المنشورات والمساهمات في المؤتمرات‬

A paper is submitted for review and possible publication in the International Journal of
Seismology entitled: “Implications of the Recent Mapping of the Offshore Thrust
Fault System on the Seismic Hazard of Lebanon” by C. Huijer · M.H. Harajli · S.
Sadek

It is also planned to present the results in the 8th International Conference on
Earthquake Resistant Engineering Structures, 7-9 Sept. 2011, Italy.
Abstract - ‫موجز عن نتائج البحث‬
Summary and conclusions
This study concentrated on evaluating the implications of the recent discovery of an offshore
thrust fault system and associated seismo-tectonic findings on the seismic hazard of Lebanon
and earlier established seismic zone parameters. The software EZ-FRISKTM was used to reassess the seismic hazard of the country through probabilistic seismic hazard analysis. An
earlier established earthquake catalogue for Lebanon and its vicinity (Harajli et al. 1994) was
further completed and expanded to cover the periods 2150 BC to AD 1896 for historical records
and 1903 to 2009 for instrumental records. Based on the earthquake catalogue, geological
studies and earlier studies undertaken to evaluate the seismic hazard of nearby countries,
potentially active seismic sources were identified, their most likely maximum magnitude and
corresponding return periods were adopted, and their magnitude-frequency relationships were
established. Several models were analyzed to account for the uncertainty with respect to the
activity of the various major faults within the LRB. Also, the sensitivity of the results to certain
assumptions made regarding the faults within the LRB as well as to the choice of attenuation
relationship was tested.
The following conclusions can be drawn from this study:
I. Lebanon is a country of moderate to high seismic hazard. The expected PGA with a
10% probability of exceedance in 50 years varies between 0.15g and 0.3g.
II. The presence of the newly discovered Mount Lebanon thrust does have an impact on the
earlier established seismic hazard of Lebanon, especially for the coastal area where
more than 70% of the country’s population and capital investments concentrate. The
proposed seismic zone parameter for the coastal area between Saida and Tripoli, as well
as for the area around the central part of the Yammouneh fault is 0.3g. The proposed
parameter for the remaining part of the country is 0.25g.