Discriminating slow slip earthquakes and sediment gravity flows from oceanographic signals: the Alaska Amphibious Community Seismic Experiment

从海洋信号中区分慢滑地震和沉积物重力流：阿拉斯加两栖社区地震实验

• 批准号: 1951071
• 负责人: Harlan Johnson
• 金额: $ 15.24万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-04-15 至 2023-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1951071&HistoricalAwards=false
• 关键词: Discriminating; slow; slip; earthquakes; sediment

Subduction zones represent the most serious seismic hazard to United States coastal population centers. The episodic but unpredictable earthquakes from these subduction zones generate undersea landslides called turbidites that produce dangerous tsunami waves that can inundate coastal cities, producing epic damage and large-scale fatalities. The 2011 Tohoku earthquake, turbidite and resulting tsunami that claimed 15,899 deaths in Japan is a recent example of this hazard, where the damage to infrastructure continues to the present day. The 1964 Magnitude 9.2 Alaska margin earthquake and tsunami was the largest seismic event to hit the United States in modern times, causing over $2.3 billion dollars in damage and pointing clearly to the potential risks of subduction zone earthquakes and tsunamis to U.S. coastal cities. The recently-conducted National Scientific Foundation Community Seismic Experiment deployed ocean bottom instruments in a 14-month off-shore experiment on the Alaska margin in order to assess this risk. An additional suite of sensors and data loggers was added to this experiment by the University of Washington, specifically to evaluate the risk from turbidite currents initiated by Alaskan margin earthquakes. Within this current project, these new data will be integrated from all of the community experiment sensors in order to (1) determine the minimum magnitude earthquake that can trigger both turbidity currents and tsunamis, (2) produce numerical models to eliminate the production of false positive alarms that are generated from non-seismic Alaskan winter storms and ocean currents, and (3) help assess the potential for the Alaska Subduction Zone margin to produce the large tsunamis that potentially threaten the west coast of the United States and Canada. The project includes support for a UW graduate student whose PhD thesis includes training in evaluating subduction zone seismic hazards, a numerical modeler who will construct an Aleutian Island regional ocean model to help evaluate false positives produced by storms and local ocean current eddies and an expert in identifying marine landslides on subduction zone margins.The recent NSF Alaska Amphibious Community Seismic Experiment deployed 74 Ocean Bottom Seismometer instruments in the 14-month off-shore experiment on the Alaska subduction zone margin. In addition, the University of Washington added an additional 105 sensors and data loggers to these seismometers, specifically to identify turbidity currents generated by both local and distant seismic activity and by non-seismic initiation due to winter storms and vigorous ocean eddy circulation. This study will leverage the availability of the Community Experiment seismic data, bottom pressure and temperature data, and the generation of a regional ocean modeling system ocean circulation model. The primary goal is to develop improved techniques to correct bottom pressure time series for oceanographic phenomena in order to optimize the identification of long-duration seismic events and sediment gravity flows. Specifically, the study will integrate the multiple observational proxies which include bottom temperature, pressures at a stable reference site, network-averaged temperatures and pressures, atmospheric pressures and sea surface heights, together with the generation of a numerical model to improve oceanographic bottom pressure predictions and corrections. The seafloor instrument pressure data will also be used to investigate the effectiveness of differencing along-isobaths rather than the traditional approach of using a deep-water single-station reference dataset. The combined Community Experiment data will also be analyzed for short-term temperature signals diagnostic of turbidity currents and more subtle signals of precursory flows and enhanced pressures from long-lived suspended sediments. If turbidity flows are identified on the Alaskan margin, seismic data and models will be used to assess the triggering mechanisms and slope stability based on swath bathymetry maps, and sediment properties obtained from archive drilling and piston cores.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

俯冲区是对美国沿海人口中心最严重的地震危害。 这些俯冲带中的情节性但不可预测的地震产生了海底滑坡，称为浊积岩，产生危险的海啸波，可淹没沿海城市，造成史诗般的损害和大规模的死亡。 2011年的Tohoku地震，浑浊和由此导致的海啸声称日本死亡15,899人是这种危害的一个例子，基础设施对基础设施的损害一直持续到今天。 1964年的9.2阿拉斯加边缘地震和海啸是现代袭击美国的最大地震事件，造成了超过23亿美元的损失，并清楚地指出了俯冲区地震的潜在风险和海啸到美国沿海城市的潜在风险。 最近由国家科学基金会社区地震实验在阿拉斯加利润率上进行了14个月的离岸实验，以评估这一风险。华盛顿大学在此实验中添加了另一套传感器和数据记录仪，特别是为了评估阿拉斯加边缘地震发起的浊流风险。 在当前的项目中，这些新数据将从所有社区实验传感器集成到（1）确定可以触发浊流和海啸的最小级地震，（2）产生数值模型，以消除从非西马斯群岛和跨越潜在的（3）群别产生的误报的产生的误报，并（3）海啸可能威胁到美国和加拿大的西海岸。 该项目包括对大学研究生的支持，其博士学位论文包括评估俯冲区地震危险的培训，该障碍是数字建模者，该危险将建造一个阿留申岛岛的区域海洋模型，以帮助评估风暴和当地海洋当前涡流产生的误报，并在俯冲区域降低了俯冲山地上的俯冲山地山地覆盖层山地山地山地山地山地山地山地上的实验量很高。在阿拉斯加俯冲带边缘的14个月近海实验中的地震计仪器。此外，华盛顿大学在这些地震米中增加了105个传感器和数据记录仪，特别是为了识别局部和遥远的地震活动以及由于冬季风暴和剧烈的海洋循环而产生的浊流。 这项研究将利用社区实验地震数据，底压和温度数据的可用性以及区域海洋建模系统海洋循环模型的生成。 主要目标是开发改进的技术，以纠正海洋现象的底压时间序列，以优化鉴定长期地震事件和沉积物重力流。 具体而言，该研究将整合多个观测代理，包括底温度，稳定的参考位点的压力，网络平均温度和压力，压力，大气压和海面高度，以及生成数值模型以改善海洋学底部压力预测和校正。海底仪器压力数据还将用于研究沿菌株差异的有效性，而不是使用深水单站参考数据集的传统方法。还将分析组合的社区实验数据，以分析浊流的短期温度信号诊断，以及对持久悬浮的沉积物的预先流量和增强压力的更微妙的信号。 如果在阿拉斯加的边缘确定了浊流，将使用地震数据和模型来评估基于宽度测深图图的触发机制和坡度稳定性，以及从档案钻孔和活塞核心获得的沉积物特性。该奖项通过评估了构成的知识范围，该奖项反映了NSF的法定任务，并反映了概念的支持者，该奖项被评估了。

项目成果

Slow Slip Detectability in Seafloor Pressure Records Offshore Alaska

阿拉斯加近海海底压力记录中的慢滑移可检测性

• DOI: 10.1029/2022jb024767
• 发表时间: 2023
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Fredrickson, Erik K.;Gomberg, Joan S.;Wilcock, William S. D.;Hautala, Susan L.;Hermann, Albert J.;Johnson, H. Paul
• 通讯作者: Johnson, H. Paul