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An Integrated Inventory Methodology for Seismic Damage Assessment
Vasudevan, RDecember 1992To estimate the damage to buildings due to an earthquake in a region, the percentage distribution or the count of buildings according to their structural class is required. The structural class is identified for a group of buildings having similar structural response in an earthquake. In past damage estimation studies, the percentage distribution or count of buildings are obtained from aggregate data sources. These aggregate data sources do not have information on individual buildings. Instead, estimates on the percentage distribution or count of buildings at the regional level are developed from land-use maps, economic data, Census data and population count. The results of the damage estimation obtained using the aforementioned methods are as accurate as the assumptions made to estimate the regional distribution of buildings according to their structural class. 
Reliable results can.be obtained if a complete inventory of buildings in a region is available. Since, such a comprehensive inventory does not exist, several data sources need to be integrated to obtain a reasonably good building inventory. This study describes the methodology for developing an integrated inventory of buildings. As an example, the methodology is implemented in the Palo Alto area. The methodology for compiling the building inventory is general enough to be used for other regions in California. The inventory compiled for Palo Alto is based on information from the Tax Assessor's datafile. This inventory is used to estimate damage to buildings. The count of buildings according to structural class is obtained at the Census block level. This is done by geographically mapping each building address in the Tax Assessor's file to a Census block using the Census' Topologically Integrated Geographic Encoding and Referencing (TIGER) file. The dollar loss from damage to buildings is estimated for different intensity earthquakes at the Census block level. The damage estimation methodology is similar to that used in ATC-13 (1985). The dollar loss due to building damage for different intensity earthquakes is summed over all Census blocks in Palo Alto, to obtain dollar loss due to damage to buildings in Palo Alto, for different intensity earthquakes. The loss due to building damage does not include damage to building contents. The study provides a schema for integrating different data sources to develop an integrated building inventory. The damage estimation performed for Palo Alto, California, demonstrates an implementation of the proposed methodology.
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Identification of High Risk Areas Through Integrated Building Inventories
Rentzis, DN1992-04The assessment of the risk to urban areas is of primary importance for decision makers, insurance and investment portfolio mangers, and government emergency and disaster mitigation planners. In this report we present a method for estimating the expected direct dollar loss from building damage in an urban area subjected to earthquakes. The method considers the probabilities of occurrence of earthquake events on any fault in the region, the distribution of buildings, their physical characteristics and earthquake resistance, and the damage potential of different class buildings. One of the key issues in damage and loss estimation is the consolidation of a building inventory that contains sufficient information on building characteristics. This report presents a method for combining building information from existing inventories using relational data base management systems (RDBMS). In particular the RDBMS ORACLETM is used for this purpose. Damageability of different classes of structures is represented by the damage-motion relationships developed by the Applied Technology Council (ATC,1985). A theoretical formulation for computing expected losses is presented in this report. The formulation utilizes the information on seismic hazard exposure, building inventories and damage-motion relationships. Integration of the information on seismic hazard, building inventories and damage potential of building classes is performed within a geographic information system (GIS). These systems are particularly useful when data are spatially distributed or results are to be displayed over a region. Building inventories for the city of Palo Alto were obtained in order to test the model. The classification of buildings was based on the information available in the inventories. When such information was insufficient for direct classification, a probability distribution of likely building classes was developed. The seismic hazard for this area was obtained using the program SHA (Lamarre, 1988). The hazard is estimated in terms of annual probabilities of exceeding peak ground acceleration at various sites. In this study, the amplification of the soil was not included although the importance of this parameter is recognized. Given the seismic exposure and building classifications, expected damage distribution was obtained and displayed using the GIS ARC/INFOTM. Damage distribution is developed for a future time period of 50 years. The dollar damage ratios obtained in this example are only for purposes of demonstrating the model rather than forecasting absolute values of damage and loss. Since building practices are relatively uniform in this location, the distribution of damage appears to be governed by the hazard exposure.
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