tailieunhanh - Methods and Techniques in Urban Engineering Part 6

Tham khảo tài liệu 'methods and techniques in urban engineering part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Spatial Analysis for Identifying Concentrations of Urban Damage 93 this area fully encompasses the major topographic features of the neighborhood and also includes some of the surrounding flatlands. As such the PPA can be used to determine if clusters are associated with the neighborhood s topographic features. 3. The events must be based on a census of the study area rather than a sampling. The PREDES inventory was developed based on detailed building-by-building . census-type inspections thus satisfying this criterion. 4. Objects in the study area must directly correspond to events in the pattern. The events were defined so as to directly correspond to masonry and mixed construction buildings that collapsed in the earthquake thereby satisfying this criterion. 5. Event locations must be proper rather than representative of a larger object. The damage event locations were taken as the centroid of a building lot however as these lots are relatively small approximately 180 m2 relative to the size of the study area approximately 750 000 m2 this is judged to be a reasonable approach for estimating the event locations. PPA techniques There are three basic approaches for conducting a PPA. The first involves determining the number of events within a given area and therefore are referred to as density-based methods. The simplest of this class of methods are quadrat counts whereby quadrats are drafted over the study area and the number of events in each is counted to determine quadrat densities. A more sophisticated but conceptually similar density-based method involves kernel density functions whereby events are summed within a series of circular regions centered at a given location within the study area. The second approach for PPA involves the determination of distances between events and is thus referred to as a distancefunction. The third approach to PPA considers spatial associations that vary locally from the larger global trends across a region of study. As .