NATO SfP PROJECT: SEISMIC HAZARD AND RISK ASSESSMENT FOR SOUTHERN CAUCASUS-EASTERN TURKEY ENERGY CORRIDOR

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1 NATO SfP PROJECT: SEISMIC HAZARD AND RISK ASSESSMENT FOR SOUTHERN CAUCASUS-EASTERN TURKEY ENERGY CORRIDOR Gülüm Tanırcan 1, Bilge Siyahi 2, Eren Uçkan 1 and Erdal Şafak 1 1-Boğaziçi University, KOERI, Istanbul, Turkey. birgore@boun.edu.tr 2-Gebze Institute of Technology, Kocaeli, Turkey. bilge.siyahi@gyte.edu.tr The Southern Caucasus-Eastern Turkey energy corridors are formed by several critical pipelines carrying crude oil and natural gas. Among them, the Baku-Tbilisi-Ceyhan (BTC) Crude Oil Pipeline and Baku-Tbilisi-Erzurum Natural Gas Pipeline (BTE) have been constructed to transport oil and gas from Azerbaijan, via Georgia, to Turkey and world markets. The BTC pipeline travels from Baku through Azerbaijan, Georgia and Turkey to the Ceyhan marine terminal on the Turkish coast of the Mediterranean. The BTE gas line follows the BTC corridor but terminates at Erzurum and connects to the Turkish pipeline system. The 1,768 km long BTC pipeline daily transports about 1% of the world's daily petroleum output, about 1 million barrels. The BTE pipeline has excess capacity today, with 30 billion cubic meters of natural gas a year. BTC and BTE Pipelines cross several active tectonic entities that have experienced large earthquakes in the past. The design of pipelines taking into account the physical and seismic properties of these entities with special emphasis on their potential of producing significant earthquakes in the future is essential and crucial, considering the high economical losses which will result from the breakdown of the system even at a single location along its route. Damage to a pipeline due to a large earthquake in one of the countries will affect directly and indirectly all the other countries that the pipeline extends, impacting large geographic regions and disrupting global economies. Past earthquakes have clearly shown that earthquakes cause major damage to pipelines, not only direct damage (such as the interruption of flow due to breakage, huge repair and restoration costs, widespread fires, environmental pollution), but also indirect economic losses due to business interruptions and disruptions on other lifelines (e.g., power, water, and communication lines). To our knowledge, none of these pipelines has ever been evaluated comprehensively (other than the standard code-based design studies) for their seismic safety and risk. None of the pipelines has any type of seismic monitoring system. The current NATO SfP project that has been carried on with Turkish, Georgian and Azerbaijan researchers aims to identify the vulnerable segments of the pipelines to earthquakes, and provide mitigation strategies by performing a comprehensive seismic hazard and risk study. The project will result 243

2 in the following products: (1) deterministic and probabilistic seismic hazard maps in Azerbaijan, Georgia and North Eastern Turkey (i.e., expected ground shaking maps) for the length of the pipelines, (2) geology and site amplification maps, (3) fragility curves for all pipeline types used in the system, (4) maps of expected damage in the pipelines for expected and scenario earthquakes, (5) a GIS-based software package to incorporate and manipulate all the maps mentioned above, and (6) specifications for a seismic monitoring system for the pipelines. INTRODUCTION The Southern Caucasus- Eastern Turkey energy corridors are formed by several critical pipelines carrying crude oil and natural gas from Azerbaijan, via Georgia, to Turkey and world markets. In civil engineering literature, such structures are commonly termed as Lifelines for the cities and countries they cross, because of their importance and the consequences of any damage to them. The two most important of these pipelines are the Baku-Tbilisi-Ceyhan (BTC) Crude Oil Pipeline and the Baku-Tbilisi-Erzurum (BTE) Natural Gas Pipeline. At a length of 1,768km, the BTC Pipeline is one of the great engineering endeavors of the 21st century. It runs 443km through Azerbaijan, 249km through Georgia and 1,076km through Turkey, ending at the Ceyhan Marine Terminal on the Mediterranean Coast. At its highest point where it crosses the Caucasus Mountains the pipeline climbs to an altitude of 2,800m. The pipeline is buried along its entire length, and includes eight pump stations, two in Azerbaijan, two in Georgia, and four in Turkey. It has a capacity to export one billion barrels of oil a day. The diameter of the pipeline varies from 42 to 38 inches, and the maximum design pressure is 100 bars. By creating the first direct pipeline link between the landlocked Caspian Sea and the Mediterranean, the BTC project brings huge economic advantages to the region, as well as reducing the oil tanker traffic through the two vulnerable Turkish Straits, the Bosporus and the Dardanelles. Operations of the BTC pipeline started up first in Azerbaijan with the beginning of linefill at the head pump station at the Sangachal terminal in Azerbaijan on 10 May A total of 10 million barrels of crude oil is required to fill the line. On 10 August 2005 the first volumes reached the Azeri-Georgian border, and on 17 November 2005 line-fill proceeded into Turkey. The first oil was loaded onto a ship on 4 June 2006 at the Ceyhan Marine Terminal with about 600,000 barrels of crude oil. This marked the start of the export of Azerbaijan s oil via the BTC oil pipeline to world markets. The official inauguration of the Turkish section of the pipeline took place at Ceyhan Marine Terminal on 13 July The path of the BTC Pipeline is shown in Figure 1. Erzurum 244 BTE BTC

3 Figure 1 Paths of Baku-Tbilisi-Ceyhan (BTC) crude oil and Baku-Tbilisi-Erzurum (BTE) natural gas pipelines. The BTE pipeline (also known as the South Caucasus Pipeline or Shah-Deniz Pipeline) is a natural gas pipeline, which closely follows the path of the BTC pipeline. It was constructed in the same corridor as the BTC pipeline in order to minimize the environmental and social impact. It transports natural gas from the Shah Deniz gas field in the Azerbaijan sector of the Caspian Sea to the city of Erzurum in Eastern Turkey. The commissioning gas was pumped to the pipeline in May 2006, and the first deliveries started in December At full capacity, the pipeline is designed to export up to 30 billion cubic meters of natural gas a year. With various agreements already signed, several new projects are underway to connect these pipelines, via Turkey, to Eastern Europe, including Greece, Italy, Bulgaria, Romania, Hungary, and Austria, as shown in Figure 2. Damage to a pipeline due to a large earthquake in one of the countries will affect directly and indirectly all the other countries that the pipeline extends, impacting large geographic regions and disrupting global economies. Figure 2 Existing and planned pipelines from Caucuses to Europe 245

4 These two pipelines cross major seismic zones that have experienced large earthquakes in the past. Figure 3 shows the tectonic plates and major fault lines in the region, whereas Figure 4 shows active faults in detail. Past earthquakes have clearly shown that earthquakes cause major damage to pipelines, not only in the form of direct damage (such as the interruption of flow due to breakage, huge repair and restoration costs, widespread fires, environmental pollution), but also indirect economic losses due to business interruptions and disruptions on other lifelines (e.g., power, water, and communication lines). To our knowledge, none of these pipelines has ever been evaluated comprehensively (other than the standard code-based design studies) for their seismic safety and risk. None of the pipelines has any type of seismic monitoring system. The objective of the proposed project is to evaluate the seismic hazard and risk on the Southern Caucasus-Eastern Turkey energy corridors, where the two Trans-Caucasian pipelines, the Baku- Tbilisi-Ceyhan (BTC) Crude Oil Pipeline and the Baku-Tbilisi-Erzurum (BTE) Natural Gas Pipeline are located. The project will help to identify the vulnerable segments of the pipelines to earthquakes, and provide mitigation strategies. The security of the prospective energy corridors between the Caspian and Central Asian energy sources, and the Western energy markets is a subject of central importance in today s international politics. As Georgia and Azerbaijan are NATO partner countries, this energy corridor itself is an embodiment of the expanding NATO security area. Therefore, assessment of natural hazards that would affect the pipeline route should be an inherent part of the security strategies for NATO. The major tasks in the project are: (1) to assess the seismic hazard in Azerbaijan, Georgia and North Eastern Turkey (2) to evaluate the seismic safety of the pipelines, (3) to develop efficient seismic risk monitoring and mitigation strategies, and (4) to improve environmental security in this part of the world. 246

5 Figure 3 Tectonic plates that controls the seismicity in Eastern Turkey and Caucuses Figure 4 Fault Map of Eastern Anatolia-Caucasus 247

6 METHODOLOGY AND PROJECT The assessment of seismic hazard and risk involves first determining the expected level of shaking by accounting for seismic sources in the region, past history of earthquakes, and local soil characteristics, and then incorporating structural inventory and the associated fragility relationships (i.e., ground shaking versus level of damage curves) into seismic hazard. Ultimate products of a seismic hazard and risk study are a series of digital GIS maps (i.e., seismic hazard maps, site amplification maps, microzonation maps, structural inventory maps, structural damage maps, and loss estimation maps), and a software package to manipulate and modify the maps to assess seismic hazard and risk. Figure 5 gives a flow chart, which summarizes the steps in seismic hazard and assessment. ENTER Historical seismicity Fault & GPS Data Probabilistic SeismicHazard Maps for a generic site Strong Motion Records Soil amplification Site-specific seismic hazard maps (microzonation) Satellite image Data from municipalities and field work Structural inventory and categorization Assessment of seismic losses and strategies for seismic risk mitigation Damage data and analytical studies Fragility curves for each structural category FIG Components from seismic hazard assessment to seismic risk reduction. Figure 5 Components of seismic hazard and risk assessment. The special characteristics of oil and gas pipelines (e.g., they are very long, usually underground, and cross several seismic, geologic, and topographic zones) require modifications to the standard seismic hazard and risk analyses that are typically done for buildings. Pipelines are investigated in segments, where the segments are determined based on the changes in seismicity, soil conditions, and pipeline characteristics. The overall seismic risk for the entire pipeline is established based 248

7 on the spatial correlation of the seismic hazard and risk for the segments. For example, a severe earthquake in Azerbaijan will not only damage the pipeline there, but also create disruption of electrical power systems in Turkey. Also, the ground motion parameters that are important for pipelines differ from those that are important for buildings. For example, seismic performance of buried pipelines is controlled by ground displacements and their spatial distribution, rather than ground accelerations. The connection of pipelines to a more rigid structure, such as a pump station, represents a critical section. Soil liquefaction is a very critical factor for pipeline damage. More on seismic hazard and risk assessment, and the behaviour of buried pipelines under earthquakes can be found in Frankel (1996), EERI (1997), Datta (1999), Wijewickreme et al. (2005), and Allouche and Bowman (2006). This project will apply the state-of-the-art probabilistic and deterministic approaches to assess the seismic hazard and risk for the BTC and BTE pipelines. The methodology will be similar to that used in an earlier NATO Science for Peace project lead by KOERI-EED, Assessment and Mitigation of Seismic Risk in Tashkent, Uzbekistan and Bishkek, Kyrgyz Republic (Project No: SfP ) (Erdik et al., 2004). This project was done jointly by Kandilli Observatory and Earthquake Research Institute in Istanbul, Turkey; the U.S. Geological Survey in Golden, Colorado, USA; Institute of Mechanics and Seismostability of Structures in Tashkent, Uzbekistan; and Institute of Seismology in Bishkek, Kyrgyz Republic. The project received an award from NATO for its scientific quality, and the final report was submitted to NATO in March After a uniform methodology is set and the computational tools are developed, each country will complete the tasks for the pipeline segments in their own country. We will then combine the results and present them for the entire pipeline. The project will include the following four tasks: 1. assessment of seismic hazard, 2. evaluation of site effects, 3. development of fragility relationships, and 4. assessment of seismic risk. TASK 1: ASSESSMENT OF SEISMIC HAZARD Assessment of seismic hazard involves development of tools and techniques to predict the intensity of ground shaking for likely earthquakes in the region. We will utilize probabilistic, as well as deterministic approaches to assess seismic hazard. PROBABILISTIC SEISMIC HAZARD MAPS The probabilistic assessment of seismic hazard involves calculation of the expected value of ground shaking for a specified probability of exceedance within a specified time period (e.g., peak ground acceleration that has a 10-perecent probability of being exceeded within the next 50 years). 249

8 Ground motion Prob. of exceedance Log(Num.Eqs.>M) Figure 6 presents schematically the steps of probabilistic hazard assessment. To calculate seismic hazard, we will utilize the methodology recently developed by the USGS (Frankel, et al., 1996). This methodology has been reviewed extensively by the scientific and the users communities in several workshops convened by the USGS, the Building Seismic Safety Council, and the Applied Technology Council in the United States. The seismic hazard and design maps that resulted from this methodology have now officially been published by FEMA as National Earthquake Hazard Reduction Program Recommended Provisions for Seismic Regulations for New Buildings in the United States (FEMA, 1997). Fault line SITE 1- SOURCES 2- RECURRENCE Source area Fault line Source area 3- ATTENUATION Magnitude M 4- PROBABILITY M3 >M2 >M1 M3 Distance M2 M1 Ground motion FIGURE 4- Steps of probabilistic seismic hazard analysis for a given site: (1) definition of earthquake sources, (2) earthquake recurrence characteristics for each source, (3) attenuation of ground motions with magnitude and distance, and (4) ground motions FIGURE 6 Steps for of specified probabilistic probability seismic of exceedance hazard analysis levels for (calculated a given by site: summing (1) definition probabilities of earthquake sources, over all the sources, magnitudes, and distances). (2) earthquake recurrence characteristics for each source, (3) attenuation of ground motions with magnitude and distance, and (4) ground motions for specified probability of exceedance levels (calculated by summing probabilities over all the sources, magnitudes, and distances). 250

9 The USGS methodology for the probabilistic assessment of seismic hazard includes the following steps: 1. Produce comprehensive earthquake catalogue with uniform magnitude scale. 2. Produce database of active faults with slip rates, estimated recurrence times, and estimated maximum magnitudes. 3. Assess appropriate attenuation relations for ground motions as a function 4. Integrate (1)-(3) into probabilistic calculation of seismic hazard curves with uncertainties. The calculations give the numerical values of various ground motion parameters (e.g., peak acceleration, peak velocity, root-mean-square acceleration, response spectra, spectral intensity, etc.) for any given probability of exceedance or return period. The data needed for the calculations include the catalogue of past earthquakes, location and the size of seismic source zones and active faults, and the attenuation equations (i.e., the equations describing the variation of ground motion parameters with magnitude and distance). We will utilize the published reports and maps, seismic data from the countries involved, and if necessary, perform field investigations to acquire new data. The products from this task will be a set of probabilistic seismic hazard maps showing peak ground accelerations and pseudo-acceleration response spectra at 0.2, 1.0, 2.0, and 4.0-sec. periods for 10% probability in 50 years, and 2% probability in 50 years. The maps will be presented in a digital format compatible with commonly used GIS software packages. DETEMINISTIC SEISMIC HAZARD MAPS The deterministic assessment of seismic hazard does not consider the time factor. Ground motions are estimated, based on the active faults and possible source zones in the region, by assuming that among the possible earthquake scenarios the worst-case scenario will occur. Figure 7 outlines the procedure for developing deterministic seismic hazard at a given location. TASK 2: ASSESSMENT OF SITE AMPLIFICATION The term Site Amplification refers to the increase in the amplitudes of seismic waves as they propagate through the soft geologic layers near the surface of the earth. Site amplification is a critical factor influencing the damage in structures during earthquakes. Soft soil layers can cause five to tenfold increase in the amplitudes of seismic waves. The probabilistic and deterministic seismic hazard maps, discussed above, are developed for a generic soil type. To determine the actual ground shaking at a specific location, the shaking values given in seismic hazard maps should be multiplied with the local site amplification factors. The resulting maps are known as Microzonation Maps. These are the maps that are used to design and evaluate structures because they represent the actual ground shaking in that location. 251

10 Ground shaking Line source SITE Source zone Point source M 1 d 3 d 1 d 2 M 2 M 3 A 1 A 2 A 3 M 1 M 2 M d 3 d 2 d 1 Deterministic seismic hazard= max(a 1, A 2, A 3 ) Figure 7 Components of deterministic seismic hazard analysis. FIG. 1 Components of deterministic seismic hazard analysis Site amplification factors can be determined from available records of past earthquakes, from the surface to bedrock geologic maps and the associated shear-wave velocities for each geologic unit, or by field tests using portable shakers and recording instruments. The geotechnical boring logs that may be available from nearby municipalities and construction companies are also useful to determine site amplification factors. When no information is available, a simple way to determine site amplification factors is to use the measurements of ambient ground noise. We plan to purchase and utilize portable seismic monitoring systems to record ambient ground noise. We will also consider using surface exciters to shake the ground and record its response. By proper analysis of ground vibrations generated by ambient forces or surface exciters, it is possible to determine site amplification factors (Safak, 2005; Safak, 2006). 252

11 We propose to purchase and use portable broadband seismic recorders with built-in threecomponent sensors to record ground noise along the pipelines. We will divide the pipelines path into several segments based on the geology and the availability of other types of data, and collect ground vibration data for about a week from each segment. TASK 3: DEVELOPMENT OF FRAGILITY RELATIONSHIPS Fragility relationships are the curves that show the variation of level of damage in a structure or a component with shaking intensity. The first step in the development of fragility curves is to compile and categorize pipeline components based on their structural behaviour during earthquakes (e.g., pipes with different materials, diameters, thicknesses; pump stations; control rooms, etc.). The next step is to determine critical shaking parameter for each category (e.g., peak ground acceleration, peak ground velocity, spectral acceleration, ground strain, etc.). The last step is to determine, for each component, the relationship between the selected ground shaking parameter and the level of damage, This last step is done by using available data from past earthquakes, laboratory testing, and analytical models. TASK 4: ASSESSMENT OF SEISMIC RISK Assessment of seismic risk involves prediction of damage to pipelines from likely earthquakes in the region. This is accomplished by combining the seismic hazard maps (including site effects) with the categorization and fragility curves done in the previous step. The result is a series of maps showing the expected level of damage and loss along the pipeline for probabilistic and scenario deterministic earthquakes. The data layers and all the maps developed in the Tasks will compiled in an easily accessible and electronically exchangeable GIS format by using a commercially available GIS package. The project will result in the following products: 1. deterministic and probabilistic seismic hazard maps (i.e., expected ground shaking maps) for the length of the pipelines, 2. geology and site amplification maps (i.e., amplification factors of shaking due to near-surface soil layers), 3. fragility curves (i.e., shaking intensity versus expected level of damage curves) for all pipeline types used in the system, 4. maps of expected damage in the pipelines for expected (i.e., probabilistic) and scenario (i.e., deterministic) earthquakes, 5. a GIS-based software package to incorporate and manipulate all the maps mentioned above, 6. specifications for a seismic monitoring system for the pipelines. 253

12 References 1. Allouche, E.N. and Bowman, A.L. (2006). Holistic Approach for Assessing the Vulnerability of Buried Pipelines to Earthquake Loads, Natural Hazards Rev., Volume 7, Issue 1, pp Datta, T.K. (1999). Seismic response of buried pipelines: A state-of-the-art review, Nuclear Engineering and Design, Vol. 192, No. 2, pp EERI (1997). Earthquake Spectra, Special Issue on Loss Estimation, Journal of the Earthquake Engineering Research Institute, Vol.13, N0. 4, November Erdik, M., Rashidov, T., Safak, E. and Turdukulov, A. (2005). Assessment of seismic risk in Tashkent, Uzbekistan and Bishkek, Kyrgyz Republic, Soil Dynamics and Earthquake Engineering, Vol. 25, No.7-10, pp Frankel, A. et al., (1996). National Seismic-Hazard Maps: Documentation, Open-File Report , U.S. Geological Survey, Denver, Colorado. 6. Safak, E. (2005). Analysis of ambient ground and structural vibration data, Annual Meeting of the Seismological 7. Society of America, Incline Village/Lake Tahoe, Nevada, April Safak, E. (2006). Seismic site characterization by using ambient noise records from portable instruments, Course Notes, 5-day in-house training course at Kuwait Institute for Scientific Research, Kuwait, March Wijewickreme, D., Honegger, D., Mitchell, A., Fitzell, T., (2005). Seismic Vulnerability Assessment and Retrofit of a Major Natural Gas Pipeline System: A Case History Earthquake Spectra, Volume 21, No.2, pp , EERI. 254