Are tunnels safe in earthquakes and tsunamis?
Structural engineers believe a tunnel is among the safest places during an earthquake because seismic waves are amplified as they reach the surface, threatening above-ground structures more than tunnels. For example, in 1989 the Loma Prieta earthquake shook the San Francisco Bay Area, collapsing a key Oakland elevated roadway but leaving the BART tunnel unscathed. It was quickly inspected and reopened. In Seattle, the Sound Transit-Metro tunnel and railroad tunnels under downtown have also survived earthquakes without damage. The tunnel’s portals would be designed to restrict the entry of water from tsunamis. In any case, it would take an extraordinary wave to reach a tunnel portal. A tsunami meeting those conditions is estimated to occur only once every 23,000 to 60,000 years. In that case, no one driving on the surface would be safe either.
