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.