Seismic risk assessment of buildings in urban areas: a case study for Denizli,Turkey

This study aims to carry out a seismic risk assessment for a typical mid-size city based on building inventory from a field study. Contributions were made to existing loss estimation methods for buildings. In particular, a procedure was introduced to estimate the seismic quality of buildings using a scoring scheme for the effective parameters in seismic behavior. Denizli, a typical mid-size city in Turkey, was used as a case study. The building inventory was conducted by trained observers in a selected region of Denizli that had the potential to be damaged from expected future earthquakes according to geological and geotechnical studies. Parameters that are known to have some effect on the seismic performance of the buildings during past earthquakes were collected during the inventory studies. The inventory includes data of about 3,466 buildings on 4,226 parcels. The evaluation of inventory data provided information about the distribution of building stock according to structural system, construction year, and vertical and plan irregularities. The inventory data and the proposed procedure were used to assess the building damage, and to determine casualty and shelter needs during the M6.3 and 7.0 scenario earthquakes, representing the most probable and maximum earthquakes in Denizli, respectively. The damage assessment and loss studies showed that significant casualties and economic losses can be expected in future earthquakes. Seismic risk assessment of reinforced concrete buildings also revealed the priorities among building groups. The vulnerability in decreasing order is: (1) buildings with 6 or more stories, (2) pre-1975 constructed buildings, and (3) buildings with 3–5 stories. The future studies for evaluating and reducing seismic risk for buildings should follow this priority order. All data of inventory, damage, and loss estimates were assembled in a Geographical Information System (GIS) database.     

Earthquake disaster risk assessment and evaluation for Turkey

Turkey is the one country in which 90% of the buildings are subject to the risk of earthquake disaster. Recent earthquakes revealed that Turkey’s present residential reinforced-concrete constructions are insufficient in earthquake resistance. Many of the buildings which collapsed or were severely damaged have been rehabilitated by applying simple methods, whose adequacy is questionable. As in Japan and the United States, Turkey’s earthquake assessment studies have increased, especially after earthquakes in 1999, In US, several methodologies and standards, such as Hazard-US (HAZUS) and Applied Technology Council (ATC) 13-20-21 and 156, provide comprehensive earthquake loss estimation methodology for post-earthquake assessment. This paper provides post-earthquake assessment and disaster management for Turkey. The main aim of the post-earthquake assessment discussed is to evaluate loss and estimate damage through disaster management approach. Classification criteria for damage are essential to determine the situation after an earthquake in both the short and long terms. The methodology includes probabilistic-based analysis, which considers the magnitude of Ms ≥ 5.0 earthquakes between 1900 and 2005, for determining the probabilistic seismic hazard for Turkey.     

Regional economic impact analysis of earthquakes in northern Taiwan and its implications for disaster reduction policies

The direct damage caused by earthquakes, such as impaired buildings, may interfere with normal business operations and disrupt the function of the industrial chain. Such economic impacts can be evaluated using the input–output analysis developed by Leontief. In this paper, two scenario earthquakes in northern Taiwan both with a return period of 475 years—the Hsinchu Hsincheng and the Yilan Nan-ao earthquakes—are simulated. The results show that the economic impact caused by the Hsincheng earthquake is greater than that resulting from the Nan-ao earthquake, which should be the major scenario considered for the disaster reduction plan. The industries affected the most are the manufacturing, food services and entertainment, storage and retail trade, and public and construction industries. The Nan-ao earthquake causes relatively more losses in the food services and entertainment industries. Most of the repercussion effects of these industries are in the central and southern parts of Taiwan. The loss to the manufacturing sector and its repercussion effects are enormous. Therefore, the government should make it a first priority to encourage the manufacturing sector to implement earthquake mitigations, such as a seismic retrofit, or to provide a seismic evaluation, which can enable firms to engage in mitigation voluntarily. The measure needed to reduce the loss in agriculture is that the government can purchase agricultural products in central and southern Taiwan following the disaster and offer them to survivors in northern Taiwan.     

Damage Survey of Water Supply Systems and Fragility Curve of PVC Water Pipelines in the Chi–Chi Taiwan Earthquake

Substantial damage to water supply systems, including water delivery pipelines, water treatment plants, reservoirs, and water storage tanks, was reported after the 1999 Chi–Chi Taiwan Earthquake. This paper first summarizes the damage survey and then presents the results of seismic fragility analysis for underground pipelines. Construction blueprints of the water delivery pipelines and repair work orders of 11 townships and cities in the disastrous area were digitized into a Geographical Information System (GIS) for analysis and assessment. With the aid of the GIS system, we found that PVC pipes made up 86% of water delivery pipelines while steel, cast iron, ductile iron, PE and others took the rest. Therefore, this paper focuses on the fragility analysis of PVC pipes. Three different methods were applied to derive the fragility relations between the PVC water pipes having nominal diameters (approximately inner diameters) greater than or equal to 65 mm and earthquake intensity parameters such as peak ground acceleration and peak ground velocity. The results were then examined with those of other countries. The discrepancy between our results and the empirical equation used by HAZUS, an earthquake loss estimation software developed by the Federal Emergency Management Agency was not significant.     

Assessment of Global Seismic Loss Based on Macroeconomic Indicators

Most earthquake loss studies use a probabilistic approach in which predicted damages in various categories of structure and facilities in the region in concern are estimated and added together to obtain a total loss for particular intensity ranges. Such an approach requires a detailed inventory database of the structures and facilities in the region, which is not always readily available in many regions of the world. We have used an alternative means of estimating earthquake losses based on several macroeconomic indices such as the gross domestic product and population. Using published earthquake loss data for 1980–1995, the relations between GDP and earthquake loss have been formulated empirically for several intensity ranges. The world's land surface was divided into unit cells 0.5° lat. × 0.5° long. in size. The GDP of each cell was apportioned based on its population and GDP, and the population of the region to which it belongs. The predicted seismic loss of the cell was then estimated from the seismic hazard probability function, its GDP, and the empirical relation between GDP and seismic loss. A global seismic loss map is then compiled both for the intensity at 10% probability of exceedance and the probable maximum intensity. Employing readily available socioeconomic data as the basis for the vulnerability analysis, the method enables us to obtain seismic loss estimates for regions without the need for a detailed inventory of exposed structures or collateral geological information. Since such statistics are frequently compiled by the world's leading political and financial institutions, the seismic loss estimates can also be upgraded easily for the fast developing areas of the world.     

The impact of a storm surge on business establishments in the Houston MSA

This paper examines the possible storm surge damage from a major hurricane to hit the Houston Metropolitan Statistical Area (MSA.) Using storm surge analysis on a unique data set compiled from the Texas Workforce Commission (QCEW), the paper estimates the expected industry-level damage for each county in the Houston MSA. The advantages of using GIS to analyze the expected storm surge damage estimation is that it provides an accurate estimation of the number of affected employees and probable wages losses, by industry and county, based on QCEW data. The results indicate that the ‘Basic Chemical Manufacturing’ and ‘Oil and Gas Extraction’ industries incur the highest employee and payroll losses while the ‘Restaurants and Eateries’ has the largest establishment damage if a major hurricane were to hit the Houston MSA.     

Seismic Hazard and Loss Estimation for Central America

A new methodology of seismic hazard and loss estimation has been proposed by Chen et al. (Chen et al., 1998; Chan et al., 1998) for the study of global seismic risk. Due to its high adaptability for regions of different features and scales, the methodology was applied to Central America. Seismic hazard maps in terms of both macro-seismic intensity and peak ground acceleration (PGA) at 10% probability of exceedance in 50 years are provided. The maps are all based on the global instrumental as well as historical seismic catalogs and available attenuation relations. Employing the population-weighted gross domestic product (GDP) data, the expected earthquake loss in 50 years for Central America is also estimated at a 5' latitude × 5' longitude resolution. Besides the seismic risk index, a measure of the relative loss or risk degree is calculated for each individual country within the study area. The risk index may provide a useful tool to help allocations of limited mitigation resources and efforts for the purpose of reduction of seismic disasters. For expected heavy loss locations, such as the Central American capital cities, earthquake scenario analysis is helpful in providing a quick overview of loss distribution assuming a major event occurs there. Examples of scenario analysis are given for San Jose, capital of Costa Rica, and Panama City, capital of Panama, respectively.     

Seismic Hazard Assessment for the Taiwan Region on the Basis of Recent Strong-Motion Data and Prognostic Zonation of Future Earthquakes

The paper describes an integrated approach to seismic hazard assessment, which was applied for the Taiwan region. First, empirical modelsfor ground motion estimation in the region were obtained on the basisof records from recent (1993-1999) earthquakes. The databaseincludes strong-motion data collected during the recent Chi-Chiearthquake (M=7.6, 21 September 1999) and large (M=6.8)aftershocks. The ground-motion database was also used for evaluationof generalised site amplification functions for typical soil classes(B, C and D). Second, the theoretical seismic catalogue (2001–2050)for the Taiwan region had been calculated using the 4D-model(location, depth, time) for dynamic deformation of the Earth' crustand 5D-model (location, depth, time, magnitude) for seismic process.The models were developed on the basis of available geophysical andgeodynamic data that include regional seismic catalogue. Third, theregion & site & time-dependent seismic analysis, which is basedon schemes of probable earthquake zones evaluated from the theoreticalcatalogue, regional ground motion models, and local site responsecharacteristics, has been performed. The seismic hazard maps arecompiled in terms of Peak Ground Acceleration (PGA) and ResponseSpectra (RS) amplitudes. The maps show distribution of amplitudesthat will not be exceeded with certain probability in condition oftypical soil classes during all possible earthquakes that may occur inthe region during time period of 2003–2025. The approach allowsintroducing new parameter that describes dependency of seismichazard on time, so-called 'period of maximum hazard'. Theparameter shows the period, during which every considered sitewill be subjected by the maximum value of ground motioncharacteristic (PGA or RS).     

Seismic Hazard and Risk Assessment for Tulbagh,South Africa: Part II – Assessment of Seismic Risk

This is the second part of our study on the assessment of seismic hazard and seismic risk for Tulbagh, the settlement, located about 90 km N-E from Cape Town, where the strongest and most damaging earthquake known in the existing earthquake history of South Africa took place. This part of our study, which can be read independently from Part I, concentrates on the probabilistic seismic risk analysis (PSRA) forTulbagh. The work begins with an introduction and a historical perspective on the estimation of seismic damage to buildings. The methodology for the estimation of expected damage from a probabilistic point of view is then presented. The work closes with an application of the described methodology to a site in the vicinity of Tulbagh.     

基于变形的土石坝地震风险分析

土石坝抗震安全的设计一般立足于预防结构的倒塌,如何使土石坝结构地震破损控制在可接受的风险水平是一个值得研究的重要课题。应用地震风险分析理论,建立了土石坝地震风险分析方法,包括地震危险性分析、地震易损性分析和地震灾害损失评估3个方面。在场地地震危险性分析基础上,将基于性能的抗震设计思想应用于土石坝结构地震易损性分析中,以土石坝坝顶相对沉陷为评价指标,划分土石坝震损等级,最后结合地震经济损失分析,建立了土石坝地震风险计算模型,在技术和经济上对土石坝地震破损风险进行分析计算。以某高土石坝为例,用该模型对大坝的震害和经济损失进行了预测分析,其结论可为土石坝安全评价及投资决策等提供依据。     

First Order Seismic Microzonation of Delhi,India Using Geographic Information System (GIS)

A first order seismic microzonation map of Delhi is prepared using five thematic layers viz., Peak Ground Acceleration (PGA) contour, different soil types at 6 m depth, geology, groundwater fluctuation and bedrock depth, integrated on GIS platform. The integration is performed following a pair-wise comparison of Analytical Hierarchy Process (AHP), wherein each thematic map is assigned weight in the 5-1 scale: depending on its contribution towards the seismic hazard. Following the AHP, the weightage assigned to each theme are: PGA (0.333), soil (0.266), geology (0.20), groundwater (0.133) and bedrock depth (0.066). The thematic vector layers are overlaid and integrated using GIS. On the microzonation theme, the Delhi region has been classified into four broad zones of vulnerability to the seismic hazard. They are very high (> 52%), high (38–52%), moderate (23–38%) and less ( < 23%) zones of seismic hazard. The “very high” seismic hazard zone is observed where the maximum PGA varies from 140 to 210 gal for a finite source model of M_w 8.5 in the central seismic gap. A site amplification study from local and regional earthquakes for Delhi region using Delhi Telemetry Network data shows a steeper site response gradient in the eastern side of the Yamuna fluvial deposits at 1.5 Hz. The ‘high’ seismic hazard zone occupies most of the study area where the PGA value ranges from 90 to 140 gal. The ‘moderate’ seismic hazard zone occurs on either side of the Delhi ridge with PGA value varying from 60 to 90 gal. The ‘less’ seismic hazard zone occurs in small patches distributed along the study area with the PGA value less than 60 gal. Site response studies, PGA distribution and destruction pattern of the Chamoli earthquake greatly corroborate the seismic hazard zones estimated through microzonation on GIS platform and also establishes the methodology incorporated in this study.     

The importance of paleoseismology in seismic hazard studies for critical facilities

This paper is intended to provide a perspective on the use of paleoseismological studies in the seismic hazard assessment of critical facilities, such as dams, chemical/petrochemical facilities and nuclear power plants. In particular, the use of data obtained from paleoseismological studies for probabilistic seismic hazard analyses, when the required probabilities of exceedance are very low (e.g. 10^{− 6}–10^{− 7}) is considered. Recent revisions to the IAEA Safety Standards that provide guidance to Member States in their work related to the seismic safety of nuclear power plants are presented to illustrate the importance of this emerging discipline.     

Correlation Fractal and Multifractal Characteristics of Seismic Activity in the Taiwan Area, China

Based on the analysis of newly collected data of plate tectonics, distribution of active faults and crustal deformation, the Taiwan area is divided into two seismic regions and six seismic belts. Then, correlation fractal dimensions of all the regions and belts are calculated, and the fractal characteristics of hypocenteral distribution can be quantitatively analyzed. Finally, multifractal dimensions Dq and f(α) are calculated by using the earthquake catalog of the past 11 years in the Taiwan area. This study indicates that (1) there exists a favorable corresponding relationship between spatial images of seismic activity described with correlation fractal dimension analysis and tectonic settings; (2) the temporal structure of earthquakes is not single but multifractal fractal, and the pattern of Dq variation with time is a good indicator for predicting strong earthquake events.     

汶川地震公路隧道普通段震害分析及震害机制研究

在汶川地震中隧道普通段出现了严重的震害,为了提高高烈度地震区隧道普通段的抗震性能,通过统计分析汶川地震公路隧道普通段震害调查资料,对隧道普通段进行了震害分析。结果表明,隧道普通段震害主要发生在软岩均一段、软硬围岩交接段软岩部分以及围岩缺陷段。通过三维有限差分数值模拟和现场典型震害分析,研究了公路隧道普通段的震害机制,探明了围岩均一普通段隧道震害机制,即硬岩隧道普通段基本无震害,软岩隧道普通段震害较严重,衬砌结构受地震惯性力影响较大,强制位移次之;探明了围岩软硬交接普通段隧道震害机制,即震害主要发生在软硬围岩交接段软岩部分,震害的主要影响因素为强制位移,地震惯性力次之;探明了围岩缺陷普通段隧道震害机制,即震害主要由地震惯性力造成强制位移影响很小。研究成果可为高烈度地震区公路隧道普通段的抗震设防提供参考。     

Evidence of self-organization in Sumatra earthquakes: recurrence time and its geodynamical implications

Risk reduction as an outcome only takes place if results of risk estimation studies are used to develop action plans for risk-management and risk-reduction strategies. This paper describes an automated model that uses the output of existing earthquake loss estimation methodologies to support decision makers in evaluating a set of competing seismic mitigation strategies and exploring their impact in reducing socio-economic losses of urban settlements. The proposed model is structured to quantify the monetary value of earthquake losses and to find an optimal budget allocation assigned to each mitigation strategy based on user input. The optimization method takes into account both pre- and post-earthquake expenditures, such as costs of building upgrades, critical facility enhancement, temporary shelter provisions, debris removal, hospitalization and human casualty. The system consists of five main modules: (1) building damage function; (2) mitigated damage function; (3) cost estimation function; (4) optimization function; and (5) user interface function. Whereas the optimization function provides the optimal values assigned to each mitigation alternative based on the estimated costs and a defined budget, the user interface allows the decision maker to interact with the software in each step and plan mitigation strategies that best suit the user’s socio-economic requirements and limitations. The outputs of the proposed model are presented with respect to an application in a pilot study area within a vulnerable city district of Tehran, Iran.     

台湾海峡西部海域沉积体系、地层架构与油气勘探前景

基于台湾海峡西部新采集的高分辨率二维地震资料及钻井数据,结合区域地质资料和前人研究成果,建立台湾海峡西部高精度等时地层格架,在此基础上厘定了地质年代属性和沉积相特征分析。研究表明第四纪地层识别出6个三级层序界面,对应地划分为5个三级层序。研究区地震相主要有席状平行—亚平行地震相、前积地震相、下切谷充填地震相、充填状低连续地震相和充填状杂乱地震相等,不同的地震相及其组合代表特定的沉积体系。通过以上分析可知研究区新生代主要发育于海陆过渡地带,主要发育冲积/洪积平原相和滨岸平原相,在此基础上分析沉积演化特征,为台湾海峡西部海域进行精细勘探提供地质依据,这对将来的油气勘探具有重要的指导意义。     

Crustal and upper mantle S-wave velocity structures across the Taiwan Strait from ambient seismic noise and teleseismic Rayleigh wave analyses

Although orogeny tapers off in western Taiwan large and small earthquakes do occur in the Taiwan Strait, a region largely untouched in previous studies owing mostly to logistical reasons. But the overall crustal structure of this region is of particular interest as it may provide a hint of the proto-Taiwan before the orogeny.By combining time domain empirical Green’s function (TDEGF) from ambient seismic noise using station-pairs and traditional surface wave two-station method (TS) we are able to construct Rayleigh wave phase velocity dispersion curves between 5 and 120 s. Using Broadband Array in Taiwan for Seismology (BATS) stations in Taiwan and in and across the Strait we are able to derive average 1-D Vs structures in different parts of this region. The results show significant shear velocity differences in the upper 15 km crust as expected. In general, the highest Vs in the upper crust observed in the coastal area of Mainland China and the lowest Vs appears along the southwest offshore of the Taiwan Island; they differ by about 0.6–1.1 km/s. For different parts of the Strait, the upper crust Vs structures are lower in the middle by about 0.1–0.2 km/s relative to those in the northern and southern parts. The upper mantle Vs structure (Moho – 150 km) beneath the Taiwan Strait is about 0.1–0.3 km/s lower than the AK135 model. The overall crustal thickness is approximately 30 km, much thinner and less variable than under the Taiwan Island. The inversion of seismic velocity structures using shorter period band dispersion data in the sea areas with water depth deeper than 1000 m should take water layer into consideration except for the continental shelves.     

Estimation of Earthquake Damage to Buried Pipelines Caused by Ground Shaking

One of the most critical lessons of the recent earthquakes is the need for seismic planning for lifelines, with appropriate supplies and back up systems for emergency repair and restoration. Seismic planning, however requires physical loss estimations before the earthquakes occur. Buried pipeline damage correlations are critical part of loss estimation procedures applied to lifelines for future earthquakes. We review the existing pipeline damage relationships only for ground shaking (transient ground deformations) in the light of recent developments and evaluate them with Denizli City, Turkey water supply system. Eight scenario earthquakes with four different earthquake magnitudes between M6 and M7 caused by two different fault ruptures (Pamukkale and Karakova-Akhan Faults) were used. Analyses were performed by using Geographical Information Systems (GIS). This high number of different scenario earthquakes made it possible to compare the pipeline damage relationships at different ground shaking levels. Pipeline damage estimations for Denizli City were calculated for each damage relationship and earthquake scenario. Relative effects of damage relationships and scenario earthquakes on the results were compared and discussed. The results were presented separately for brittle, ductile, and all pipelines. It was shown that the variation in ductile pipeline damage estimations by various relationships was higher than the variation in brittle pipeline damage estimations for a particular scenario earthquake.