Friday, December 21, 2018

2005年由列治文市和三角洲市政府，委託西門菲沙大學進行研究列治文島嶼和三角洲社區的海嘯風險。由 John Clague博士和 Ian Hutchinson博士研究報告發現在過去的4000年裡，儘管地質學家認為在此期間，在溫哥華島西部的卡斯卡迪亞俯衝帶上有許多巨型地震（里氏8級），但沒有證據表明菲沙三角洲曾經遭受重大海嘯影響。
但是我們必須學習緊急應變的知識，因為我們都有機會住在高風險地區和旅行。https://www.richmond.ca/safety/prepare/city/hazards/tsunamis.htm

通過 www.flood.firetree.net 網站可以查看海水上升對各大陸的影響。也可以來看看不同海水高度對大溫的影響情況。

Tsunamis

The word "tsunami" is from the Japanese words tsu (harbour) and nami (wave). Tsunamis are large wave events resulting from a significant displacement of water. These are caused by occurrences such as underwater earthquakes, underwater landslides, land-based landslides, a major oceanic volcanic eruption and less commonly, a meteorite oceanic landing.

Richmond is Not at Significant Risk of Tsunamis

While Richmond is an island community, we are not at significant risk of a tsunami. A 2005 study commissioned by the City of Richmond and the Corporation of Delta was prepared by Dr John Clague and Dr Ian Hutchinson of the Simon Fraser University (SFU). The study found no evidence that a significant tsunami has impacted the Fraser River delta, from any source, in the last 4000 years. This is despite the fact that during this period geologists believe there were numerous mega-earthquakes (magnitude 8+ on the Richter Scale) along the Cascadia subduction zone lying west of Vancouver Island.

The reason Pacific generated tsunamis do not impact the Fraser River delta is because Vancouver Island lies between the two, which creates a kind of breakwater or natural protective barrier that absorbs the major impact of a tsunami. To prove this theory, scientists have computer modelled Pacific Ocean tsunami waves (generated close to Vancouver Island) as they move down the Juan de Fuca Strait, into the Georgia Strait and finally to the western delta shore. The model predicted that during this journey wave energy would dissipate so much that any wave reaching the western delta shore would be less than 0.5m high.

The evidence that no significant tsunami has impacted the delta area in the last 4000 years is further supported by the 2003 study Numerical Modeling of Tsunamis Generated by Hypothetical Landslides in the Strait of Georgia, BC. This study modelled hypothetical underwater landslides between Roberts Bank and the Fraser River delta. It found that, while a significant landslide could generate an 18m high wave at Galiano Island, the local shoreward moving wave from a major slide would be only 2m high. This, in part, is due to the submerged banks ability to deflect wave energy away from the shoreline. The study also suggested that if a 2m high wave occurred its energy, and therefore its ability to flood land, would be dissipated by the Fraser River Delta’s wide tidal flats. It is therefore believed that any wave generated by an underwater landslide at Sturgeon Bank would not pose a significant flood risk to the City. This is due to the waves relatively small height potential, the 6 km wide tidal flats that a wave would have to cross to reach the City dyke and the fact that the City’s dyke stands approximately 3.5m above mean sea level.

Hypothetical tsunamis generated from other sources, such as land-based landslides and underwater earthquakes in the Georgia Strait, have not been extensively studied. However, as there is no evidence that significant tsunamis have occurred in the past 4000 years, the City considers it highly unlikely that such sources could trigger a significant tsunami.

For a summary of the 2005 study conducted by SFU, please follow the link: Tsunami Hazard at the Fraser River Delta, BC.

In the Event of a Tsunami In the event of a Tsunami in the Pacific Basin, the Province will alert local governments and broadcast warnings over local radio stations. In response to this, some local governments in high-risk areas, such as on the west coast of Vancouver Island, may initiate emergency evacuation procedures. Due to the insignificant risk to Richmond, the City has no plans to instigate an emergency evacuation for a tsunami.

Evacuation
If following an incident evacuation of the community is necessary, the routes used will be based on an assessment of the damage at the time of the emergency. Evacuation instructions including safe routes would be broadcast over the radio, so we recommend that you include a battery operated radio as part of your emergency supplies.

Disaster Response Routes have been designated throughout Richmond and the Lower Mainland as routes for first responders. Fire, police, ambulance and public works crews will require quick access to emergency sites to help rescue victims, fight fires, secure the emergency scene, distribute supplies and critical resources and transport the injured to the hospitals. Residents are asked to stay off these routes when activated unless directed otherwise by emergency personnel.

How You Can PrepareAs with any potential disaster individuals, families and businesses need to be prepared to survive on their own for a minimum of 72 hours and up to 7 days. To help you prepare, the Emergency Preparedness section of the City’s website offers tips on what emergency supplies you should have, how to develop a family emergency plan and how to protect yourself during earthquakes and other natural hazards.

Reception Centres
During an emergency, the City may establish a reception centre to assist evacuees in areas affected by the emergency. A reception centre is any safe gathering place, such as a community centre, church or hotel conference room where individuals may obtain information and receive assistance. Services such as family reunification, food, clothing, emergency first aid and lodging arrangements are typically performed at Reception Centres by City of Richmond staff and volunteers. For more information please refer to the Reception Centres section of the website.

The largest earthquakes around BC https://www.volcanodiscovery.com/earthquakes/british-columbia/largest.html