Constraints on Slow Slip Behavior in Cascadia Through the Integration of PBO Borehole Strainmeters, GPS Time Series, and Tremor Locations

通过集成 PBO 钻孔应变仪、GPS 时间序列和震颤位置来约束卡斯卡迪亚的慢滑移行为

• 批准号: 1251954
• 负责人: David Schmidt
• 金额: $ 27.97万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1251954&HistoricalAwards=false
• 关键词: Constraints; Slow; Slip; Behavior; Cascadia

Slow slip events and non-volcanic tremor provide new insight into the mode of strain release along the deep extension of faults. These events are noteworthy for their long durations (~days) and large magnitudes (~M6). We have yet to fully understand what properties or conditions on the plate interface act to prevent the rapid slip that is typically observed with earthquakes. Slow slip and tremor also constrain the lower edge of the seismogenic zone, a variable that is useful for seismic hazard studies, and event histories are an input into studies that explore the time-dependent loading of stress on the seismogenic zone. Most of the existing geodetic studies of slow slip have focused on observations made by GPS. In this work, we integrate borehole strainmeters with GPS data to more fully characterize the spectrum of slow slip behavior on the Cascadia subduction zone. Time-dependent inversions of GPS and strainmeter time series are performed using the Extended Network Inversion Filter. By incorporating the strainmeters into our analysis, we resolve smaller slow slip events and extract greater information about the propagation characteristics than by using GPS alone. From our expanded catalog of slow slip events, we are extracting the source parameters and testing whether the smaller slow slip events (~M5+) obey the same scaling relationships as has been inferred for the larger ones (~M6+). The strainmeter data also allow us to better compare the spatial and temporal correlation of slow slip and the location of tremor. We are testing the idea of whether tremor marks the leading edge of slow slip or whether tremor is embedded within the slipping zone. Lastly, we are evaluating the up-dip taper of slow slip and seeing if the surface observations are consistent with an abrupt up-dip edge, as suggested by the tremor. Our analysis of the strainmeter data allows us to better evaluate the calibration and noise characteristic of the strainmeter time series. We will specifically use the GPS-derived slip models to independently validate the strainmeter calibrations.

慢速事件和非volcolcanic震颤为沿故障的深度扩展提供了新的洞察力。 这些事件在漫长的持续时间（〜天）和大幅度（〜M6）中值得注意。 我们尚未完全了解板界面上的特性或条件，以防止通常在地震中观察到的快速滑移。 慢滑动和震颤还限制了地震生成区的下边缘，这是一个可用于地震危险研究的变量，事件历史是对探索地震生成区应力的时间依赖性压力的研究的输入。 大多数现有的慢滑道测量研究都集中在GP的观察结果上。 在这项工作中，我们将井眼应变器与GPS数据集成在一起，以更充分地表征卡斯卡迪亚俯冲带慢速行为的频谱。 使用扩展网络反转滤波器进行GPS和应变计时间序列的时间依赖性反转。 通过将应变器纳入我们的分析中，我们可以解决较小的慢速事件，并提取有关传播特性的更多信息，而不是单独使用GPS。 根据我们扩展的慢速事件目录，我们正在提取源参数，并测试较小的慢速事件（〜m5+）是否遵守与较大的缩放关系（〜m6+）相同的缩放关系。 应变计数据还使我们能够更好地比较慢滑的空间和时间相关性和震颤的位置。 我们正在测试震颤是否标志着慢滑的前缘或震颤是否嵌入滑板区域的想法。 最后，我们正在评估慢速滑移的上倾角锥度，并查看表面观测是否与突然的上浸边缘一致，如震颤所建议的那样。 我们对应变计数据的分析使我们能够更好地评估应变计时间序列的校准和噪声特征。 我们将专门使用GPS衍生的滑移模型独立验证应变计校准。