An Integrated Inventory Methodology for Seismic Damage Assessment

To 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.