Abstract:
The seismic vulnerability of 79 churches (65% timber, 16% reinforced concrete (RC), 13% unreinforced masonry (URM), and 6% concrete block) owned by the Anglican Diocese of Waikato and Taranaki, New Zealand has been assessed. Two types of seismic scenarios have been produced using the latest version of New Zealand’s National Seismic Hazard Model and RiskScape tool. The seismic scenarios produced are (1) the most likely events at 500-, 1000- and 2500- year return periods for each church location, and (2) a series of large earthquakes affecting New Zealand’s North Island. Expected global damage levels for each church have been derived for each of the proposed scenarios using the macroseismic method, where the seismic hazard is defined by the intensity and correlated to post seismic damage. The macroseismic method used has been recently developed, and is specifically designed for New Zealand URM churches, based on a widely tested approach for European historical buildings. Preliminary vulnerability curves generated for the URM churches estimate Modified Mercalli Intensities (MMI) between 6.5 and 9.0 and mean damage grades between 1 (light damage) and 3 (severe damage) based on the EMS-98 classification of damage to masonry buildings. Using the RiskScape tool, preliminary economic loss estimations have been obtained based on asset value data, and casualty estimations have been evaluated for each church. Given the design level earthquake for each church, all timber and concrete block churches were estimated to have either no damage or light damage. Using the median estimate, 15% (2) of the RC churches and 40% (4) of the URM churches were estimated to have moderate damage, and 50% (5) of the URM churches were estimated to have severe damage. No churches were estimated to cause a death when subjected to their design level earthquake, and 89% (70) of churches were estimated to have a ratio of repair cost to replacement cost of less than 10%.