Singapore

Singapore occupies a small island at the southern tip of the Malay Peninsula, sitting on the stable Sunda Shelf. The island is geologically underlain by granite and sedimentary rocks of Triassic and older age, part of the same stable Sundaland crustal block that underlies most of Peninsular Malaysia. Singapore has no active [[fault]] systems and no history of locally generated damaging earthquakes. The nearest significant earthquake source is the Sunda subduction zone approximately 600 kilometres to the southwest in Sumatra, and the Sumatran Fault system. Singapore's primary seismic concern is not ground shaking from local earthquakes but rather the transmission of long-period [[seismic-wave]]s from distant Sumatran megathrust events.

Singapore's modern seismic experience is dominated by felt shaking from Sumatran earthquakes. The 2004 Sumatra-Andaman earthquake (magnitude 9.1) caused minor panic in Singapore as tall buildings swayed. The 2005 Nias earthquake (magnitude 8.7) was widely felt. The 2009 Sumatran earthquakes, the 2010 Mentawai earthquake (magnitude 7.8), and subsequent large Sumatran events have all been felt in Singapore's high-rise buildings. These distant earthquakes do not cause structural damage to well-built modern buildings, but the long-period sway in skyscrapers can cause discomfort, interrupt office work, and occasionally trigger building evacuations. Older buildings, swimming pools (which experience sloshing), and tall chimneys are most susceptible to these long-period waves.

The geological stability of Singapore's bedrock means that building-to-bedrock amplification of [[seismic-wave]]s is minimal, though the soft marine clay (called "marine clay" or "Old Alluvium") underlying parts of the reclaimed land could amplify certain wave frequencies. Singapore's Building and Construction Authority has adopted seismic design considerations for tall buildings, primarily to address the effects of long-period Sumatran waves. The absence of active local faults means that Singapore does not require the strong-motion seismic design criteria applied in countries directly on active plate boundaries. The primary disaster management concern for Singapore from seismic events is thus indirect — primarily through the propagation of waves from distant Sumatran earthquakes and the theoretical tsunami hazard from a Sunda Arc megathrust event.