By the EERI Reconnaissance Team.
March 19, 2011. Earthquake Engineering Research Institute.
Concerns of progressive collapse of marginally-stable structures has raised questions regarding the need to reinspect buildings following aftershocks.
The aftershock sequence has contained about 40 events greater than 4.0 and 12 events greater than 4.5 since 22 February. Most of these aftershocks occured at a depth of 2-5 km and within 10 km of the central business district. In order to quickly assess the need for re-inspections, the EOC identified a sample of damaged structures, some of which have significant residual displacements. These “indicator” buildings represent URM, RM, RC, and PC structures typical of Christchurch. Increased damage in an indicator building following an aftershock triggers re-evaluation of all corresponding buildings. The indicator building evaluations following the 4.9 M event on 6 March did not reveal additional structural damage. Some of the indicator buildings are shown below (Figures 1, 2, 3, 4).
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| Figure 1. | Figure 2. |
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| Figure 3. | Figure 4. |
Learning from Earthquakes: First person reports
