LaHusen S R, Duvall A R, Booth A M, Grant A, Mishkin B A, Montgomery D R, Struble W, Roering J J, Wartman J
Department of Earth and Space Sciences, University of Washington, Box 351310, Seattle, WA 98195, USA.
Geology, Minerals, Energy, and Geophysics Science Center, U.S. Geological Survey, 350 N. Akron Road, Moffett Field, CA 9403, USA.
Sci Adv. 2020 Sep 16;6(38). doi: 10.1126/sciadv.aba6790. Print 2020 Sep.
The coastal Pacific Northwest USA hosts thousands of deep-seated landslides. Historic landslides have primarily been triggered by rainfall, but the region is also prone to large earthquakes on the 1100-km-long Cascadia Subduction Zone megathrust. Little is known about the number of landslides triggered by these earthquakes because the last magnitude 9 rupture occurred in 1700 CE. Here, we map 9938 deep-seated bedrock landslides in the Oregon Coast Range and use surface roughness dating to estimate that past earthquakes triggered fewer than half of the landslides in the past 1000 years. We find landslide frequency increases with mean annual precipitation but not with modeled peak ground acceleration or proximity to the megathrust. Our results agree with findings about other recent subduction zone earthquakes where relatively few deep-seated landslides were mapped and suggest that despite proximity to the megathrust, most deep-seated landslides in the Oregon Coast Range were triggered by rainfall.
美国太平洋西北部沿海地区存在数千处深层滑坡。历史上的滑坡主要由降雨引发，但该地区在长达1100公里的卡斯卡迪亚俯冲带巨型逆冲断层上也容易发生大地震。由于上一次9级地震破裂发生在公元1700年，因此对于这些地震引发的滑坡数量知之甚少。在此，我们绘制了俄勒冈海岸山脉9938处深层基岩滑坡的地图，并利用地表粗糙度测年法估计，在过去1000年里，过去的地震引发的滑坡不到滑坡总数的一半。我们发现滑坡频率随年平均降水量增加而增加，但与模拟的地面峰值加速度或与巨型逆冲断层的距离无关。我们的结果与其他近期俯冲带地震的研究结果一致，在这些研究中，绘制的深层滑坡相对较少，这表明尽管靠近巨型逆冲断层，但俄勒冈海岸山脉的大多数深层滑坡是由降雨引发的。
