the effect of aftershocks on structural lifetime

Structures are generally under the risk of earthquake events, especially in regions with high seismicity. however, rather than occur individually, the seismic events tend to happen in sequence of the mainshock and the multiple aftershocks, which would cause additional damage to the damaged buildings in post-mainshock environment and increase the probability of collapse (figure 1). when a mainshock occurs, it will be generally followed by a sequence of ground motions with relatively lower intensities. these small following seismic events are called “aftershocks”. despite aftershocks usually having smallerintensities than their preceding mainshocks, their higher rate of occurrence will leave less time for repair or retrofit of thedamaged buildings. furthermore, if a building is considerably damaged in the mainshock event, the aftershocks will bemore likely to cause further damage to the building, leading to the extra financial loss and fatalities. the downtime for building repairing after the seismic events would therefore be elongated with the occurrence of aftershocks. hence, it is necessary to take the mainshock-aftershock sequence effect into consideration when performing seismic risk analysis(yeo & cornell, 2005).