Reducing risk from crustal earthquakes in western Canada

加拿大西部是加拿大最容易发生地震的地区。世界上一些最大的地震都发生在这个地区，包括1700年温哥华岛以西发生的9级卡斯卡迪亚俯冲地震；1949年夏洛特女王群岛以西发生的8.1级地震；以及发生在阿拉斯加的7.9级迪纳里断层地震，地震发生在距育空地区边界不到100公里的地方。其他大型破坏性的地壳地震包括1918年的7级地震和1946年的7.3级地震，都发生在温哥华岛，以及1872年弗雷泽河谷以南的7级地震。这些地壳地震对BC省西南部的人口中心，以及整个加拿大西部的关键基础设施构成威胁，包括育空地区和西北地区的管道，加拿大西部的水电大坝和输电基础设施，以及BC省的港口设施。了解地壳地震的重要性在日本神户6.9级地震中得到了证明，那次地震造成了超过3000亿美元的损失。然而，加拿大西部的地壳地震是个谜。这里有大型的地壳断层，如德纳里断层、Tintina断层和弗雷泽断层，但是在历史上这些构造上没有观察到大量的地震活动。在不列颠哥伦比亚省西南部，大地壳地震发生的地方（例如，1946年温哥华岛中部），没有地表断层的证据，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——它们可能发生在哪里，它们可能有多大，它们可能发生的频率，以及地面将如何震动。我们将通过识别活动结构，绘制断层的滑动分布和破裂过程，以及绘制地震产生的应力场来做到这一点。这些研究的结果将被纳入加拿大国家建筑规范的地震危险图，并将为工程应用提供有用的波形。反过来，这将有助于减少该地区未来地震的损失和经济影响。这类研究给社会带来的好处可以达到数十亿美元。

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.