A study of tunnels in areas affected by strong earthquakes in the last 50-100 years revealed at least three cases of tunnels damaged by earthquake shaking or offset by seismic faulting, including the Bolu (Turkey) twin tunnels, which collapsed during the 1999 Düzce earthquake. These data indicate that tunnels cannot be considered as structures invulnerable to earthquakes. Furthermore, the tectonic offset of tunnels shows that certain observed seismic surface ruptures are not necessarily indicative of tectonic faulting and represent only secondary local ground instability effects.

A study of tunnels in areas affected by strong earthquakes in the last 50-100 years revealed at least three cases of tunnels damaged by earthquake shaking or offset by seismic faulting, including the Bolu (Turkey) twin tunnels, which collapsed during the 1999 Düzce earthquake. These data indicate that tunnels cannot be considered as structures invulnerable to earthquakes. Furthermore, the tectonic offset of tunnels shows that certain observed seismic surface ruptures are not necessarily indicative of tectonic faulting and represent only secondary local ground instability effects.