The PLUM (Propagation of Local Undamped Motion) earthquake early warning (EEW) algorithm differs from typical source-based EEW algorithms as it predicts shaking directly from observed shaking without first deriving earthquake source information (e.g., magnitude and epicenter). Here, we determine optimal PLUM event detection thresholds for U.S. West Coast earthquakes using two data sets: 558 M3.5+ earthquakes (California, Oregon, Washington; 2012–2017) and the ShakeAlert test suite of historic and problematic signals (1999–2015). PLUM computes Modified Mercalli Intensity (I_MMI) using velocity and acceleration data, leveraging co-located sensors to avoid problematic signals. An event detection is issued when the observed I_MMI exceeds a given threshold(s). We find a two-station detection method using I_MMI trigger thresholds of 4.0 and 3.0 for the first and second stations, respectively, is optimal for detecting M4.5+ earthquakes. PLUM detected 79 events in the 2012–2017 data set, reporting (not including telemetry or alert dissemination) detection times on par, and sometimes faster than current EEW methods (mean 8 s; median 6 s). As expected, detection times were slower for the older 1999–2015 earthquakes (N = 21; mean 11 s; median 6 s) when station coverage was sparser. Of the 31 PLUM detected M5+ events (10 2012–2017; 21 1999–2015), theoretically 20 (∼65%) could provide timely warnings. PLUM issued no false detections and avoided issuing detections for all calibration/anomalous signals, regional and teleseismic events. We conclude PLUM can successfully identify I_MMI 4+ shaking from local earthquakes and could complement and enhance EEW in the U.S.

中文翻译：

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PLUM 地震预警算法：美国西海岸数据的回顾性案例研究

PLUM（局部无阻尼运动传播）地震预警 (EEW) 算法与典型的基于震源的 EEW 算法不同，因为它直接根据观测到的震动预测震动，而无需首先获得震源信息（例如震级和震中）。在这里，我们使用两个数据集确定美国西海岸地震的最佳 PLUM 事件检测阈值：558 次 M3.5+ 地震（加利福尼亚、俄勒冈、华盛顿；2012-2017）和历史和有问题信号的 ShakeAlert 测试套件（1999-2015） ）。PLUM单位计算改性麦加利烈强度（我_MMI），使用速度和加速度数据，利用共同定位的传感器，以避免有问题的信号。当观察到的I _MMI时发出事件检测超过给定的阈值。我们发现第一和第二站分别使用4.0 和 3.0 的I _MMI触发阈值的双站检测方法是检测 M4.5+地震的最佳方法。PLUM 在 2012-2017 数据集中检测到 79 个事件，报告（不包括遥测或警报传播）检测时间相当，有时比当前的 EEW 方法更快（平均 8 秒；中位数 6 秒）。正如预期的那样，1999-2015 年较早的地震（N = 21; 平均 11 秒；中位数 6 s)，当站点覆盖较稀疏时。在 PLUM 检测到的 31 个 M5+ 事件（10 个 2012-2017 年；21 个 1999-2015 年）中，理论上有 20 个（~65%）可以提供及时的警告。PLUM 没有发布错误检测并避免为所有校准/异常信号、区域和远震事件发布检测。我们得出的结论是，PLUM 可以成功地识别来自当地地震的I _MMI 4+ 震动，并且可以补充和增强美国的 EEW