Reducing risk from crustal earthquakes in western Canada

加拿大西部是加拿大地震灾害最严重的地区。该地区发生了一些世界上最大的地震，包括1700年在温哥华岛以西发生的9级卡斯卡迪亚俯冲地震；1949年在夏洛特女王群岛以西发生的8.1级地震；以及阿拉斯加7.9级德纳利断层地震，该地震破裂到育空边界100公里以内。其他破坏性较大的地壳地震包括1918年7级地震和1946年7.3级地震，这两次地震都发生在温哥华岛上，以及1872年弗雷泽山谷以南的7级地震。这些地壳地震对卑诗省西南部的人口中心和整个加拿大西部的关键基础设施构成威胁，包括育空和西北部的管道、整个加拿大西部的水电站大坝和输电基础设施以及卑诗省的港口设施。日本神户6.9级地震造成了3000多亿美元的损失，这证明了了解地壳地震的重要性。然而，加拿大西部的地壳地震令人费解。有大规模的地壳断层，如德纳利断层、廷蒂纳断层和弗雷泽断层-然而在历史时期这些构造上没有观察到明显的地震活动。在公元前西南部，那里发生了大的地壳地震(例如，1946年的温哥华岛中部)--没有证据表明地表有断层作用，因此“活动断层”可能隐藏在深处。这项拟议研究的长期目标是更好地了解加拿大西部的地壳地震--它们可以在哪里发生，规模有多大，可能发生的频率有多高，以及地面将如何震动。我们将通过识别活动构造，绘制沿断层的滑动分布和破裂过程，以及绘制地震应力场来实现这一点。这些研究的结果将被纳入加拿大国家建筑规范中的地震危险图，并将提供对工程应用有用的波形。反过来，这将有助于将该地区未来地震的损失和经济影响降至最低。这种类型的研究给社会带来的好处可能高达数十亿美元。

Western Canada is subject to the greatest seismic hazard in Canada. Some of the world's largest earthquakes have occurred in this region, including the magnitude (M) 9 Cascadia subduction earthquake to the west of Vancouver Island in 1700; the M=8.1 earthquake just to the west of the Queen Charlotte Islands in 1949; and the M=7.9 Denali Fault earthquake in Alaska, which ruptured to within 100 km of the Yukon border. Other large, damaging crustal earthquakes include the 1918 M=7 event and the 1946 M=7.3 event, both on Vancouver Island, and the M=7 earthquake just south of the Fraser Valley in 1872. These crustal earthquakes pose a threat to the population centres of southwest BC, and also to critical infrastructure throughout western Canada, including pipelines in the Yukon and NWT, hydroelectric dams and transmission infrastructure throughout western Canada, and port facilities in BC. The importance of understanding crustal earthquakes was demonstrated by the M=6.9 Kobe, Japan earthquake that caused more than $300B dollars in damage. However, crustal earthquakes in western Canada are enigmatic. There are large-scale crustal faults, such as the Denali Fault, Tintina Fault, and Fraser Fault - however no significant amount of seismicity has been observed on these structures during historic times. In southwestern BC, where large crustal earthquakes have occurred (e.g., 1946 central Vancouver Island) - there is no evidence for surface faulting, and so the "active fault" may be hidden at depth. The long-term goal of this proposed research is to better understand crustal earthquakes in western Canada - where can they occur, how large can they be, how often might they occur, and how will the ground shake. We will do this by identifying active structures, mapping the slip distribution and rupture process along faults, and mapping the earthquake-generating stress field. The results of these studies will be incorporated into seismic hazard maps in the National Building Code of Canada, and will provide waveforms useful for engineering applications. This, in turn, will help to minimise losses and economic impact of future earthquakes in this region. The benefits to society from this type of research can be in the billions of dollars.