The earthquake was an intraslab event within the Juan de Fuca plate. It was a result of
normal faulting within the descending slab, but it has not been possible to determine which of the two possible fault planes indicated by the
focal mechanism is correct. Most of the property damage occurred very near the epicenter or in unreinforced concrete or
masonry buildings, such as those in the
First Hill,
Pioneer Square, and
SoDo neighborhoods of
Seattle. The
Trinity Parish Church on First Hill was severely damaged. The
air traffic control tower at
Seattle–Tacoma International Airport was heavily damaged; it has since been replaced with a more earthquake-resistant tower. The quake splintered a buttress under the dome of the
capitol building in Olympia, but previous earthquake-resistance work prevented more serious harm to the building. Additionally, power outages affected downtown Seattle. The
U.S. Military's
Ft. Lewis and McChord Air Force Base received damage and there was very slight damage in Victoria, British Columbia. ShakeMap for the event. Following the quake, many buildings and structures in the area were closed temporarily for inspection. This included several bridges, all state offices in Olympia, and
Boeing's factories in the
Seattle area. Various schools in the state also closed for the day. The Fourth Avenue Bridge in downtown Olympia was heavily damaged and was later torn down and re-built. In Seattle, the
Alaskan Way Viaduct and
its seawall were damaged, forcing the viaduct to close for emergency repairs and ultimately factoring into the decision to replace the viaduct with the
SR 99 Tunnel and an expanded
Alaskan Way on the footprint of the old viaduct. The new tunnel is designed to withstand a 9.0 MW earthquake. Approximately $305 million of insured losses and a total of $2 billion worth of damage was caused in the state of Washington. The area was declared a natural disaster area by president
George W. Bush and was therefore able to receive federal recovery assistance. The number of businesses in the heavily affected region was relatively small. At least 20% of businesses surrounding the heavily affected area took direct losses, while 2% had direct losses of over $10,000. None of these businesses received money for direct damage from federal aid or insurance.
Ground effects Named after the
Nisqually Delta, this earthquake hit the southern end of Puget Sound causing damage to the ports of Seattle and
Tacoma. Soil liquefaction was also observed at the
Nisqually National Wildlife Refuge causing damage to the buildings within. ==Response==