A GIS based assessment of seismic risk for Wellington City

Abstract

This research develops a deterministic seismic risk assessment for Wellington City.  Expected losses to residential commercial, and industrial buildings resulting from two scenario earthquakes are calculated.  In addition, expected losses to residential and working populations as a result of property damage are determined.

Findings are based on: (1) a microzonation of the earthquake hazard; (2) an inventory of buildings by value, use, floor area, and conditions; (3) damage ratios defining the seismic performance of buildings: (4) data on the density and travel paths of day and night-time population; and (5) seismic casualty functions defining casualty risk as a function of building damage.  This analysis is greatly facilitated by the algebraic combination of digital map layers within a vector-based geographical information system.

Results indicate that a large, local, shallow earthquake will cause losses in excess of $3718 million (19.9 percent of total replacement value).  Greater casualty numbers are expected to result from a daytime occurrence of this scenario earthquake than from the same event occurring at night.  Triangular irregular network models are used to show the expected distribution of casualties.