Alert Optimization of the PLUM Earthquake Early Warning Algorithm for the Western United States
Alert Optimization of the PLUM Earthquake Early Warning Algorithm for the Western United States
复制标题
DOI：
10.1785/0120210259
复制
发表时间：
2022-04-01
影响因子：
3
通讯作者：
Kodera, Yuki
中科院分区：
文献类型：
--
作者：
Cochran, Elizabeth S.;Saunders, Jessie K.;Kodera, Yuki
我们确定了一个最佳的报警配置的传播本地无阻尼运动（PLUM）地震预警（EEW）算法，用于美国ShakeAlert系统覆盖加州，俄勒冈州，和华盛顿。所有EEW系统都应平衡以下主要目标：对有影响或潜在破坏性的震动及时发出警报，同时限制对太低而不值得关注的震动发出警报（预防性警报）。PLUM EEW算法在不考虑衰减的情况下，将观测到的地面运动向前预测到定义半径内的附近场地，避免了大多数EEW算法的震源参数估计步骤。PLUM最初是在日本开发的，其中发出警报的警报区域和地面运动与ShakeAlert实施的不同。我们比较了预测的地面运动从PLUM地震图报告的地面运动的一组22美国西海岸4.4-7.2级地震，并评估可用的预警时间。我们研究了一系列的预测半径（20-100公里），用于发出警报的阈值（警报阈值），以及影响或潜在破坏性震动的水平（目标阈值）。我们发现最佳性能时，警报阈值接近目标阈值，虽然较高的目标地面运动受益于较低的警报阈值，以确保及时报警。我们还发现，性能，衡量的成本降低，用户可以实现，取决于用户的容忍预防警报。当使用较大的预测半径（60-100公里）时，目标阈值低、对预防警报容忍度高的用户可实现最佳性能。相比之下，具有高目标阈值和对预防警报的低容忍度的用户在较小的预测半径（30-60公里）下实现更好的性能。因此，将PLUM预测半径设置为60 km可以平衡许多用户的需求，并提供最长约20 s的预警时间。
We determine an optimal alerting configuration for the propagation of local undamped motion (PLUM) earthquake early warning (EEW) algorithm for use by the U.S. ShakeAlert system covering California, Oregon, and Washington. All EEW systems should balance the primary goal of providing timely alerts for impactful or potentially damaging shaking while limiting alerts for shaking that is too low to be of concern (precautionary alerts). The PLUM EEW algorithm forward predicts observed ground motions to nearby sites within a defined radius without accounting for attenuation, avoiding the earthquake source parameter estimation step of most EEW algorithms. PLUM was originally developed in Japan where the alert regions and ground motions for which alerts are issued differ from those implemented by ShakeAlert. We compare predicted ground motions from PLUM to ShakeMap-reported ground motions for a set of 22 U.S. West Coast earthquakes of magnitude 4.4-7.2 and evaluate available warning times. We examine a range of prediction radii (20-100 km), thresholds used to issue an alert (alert threshold), and levels of impactful or potentially damaging shaking (target threshold). We find optimal performance when the alert threshold is close to the target threshold, although higher target ground motions benefit from somewhat lower alert thresholds to ensure timely alerts. We also find that performance, measured as the cost reduction that a user can achieve, depends on the user's tolerance for precautionary alerts. Users with a low target threshold and high tolerance for precautionary alerts achieve optimal performance when larger prediction radii (60-100 km) are used. In contrast, users with high target thresholds and low tolerance for precautionary alerts achieve better performance for smaller prediction radii (30-60 km). Therefore, setting the PLUM prediction radius to 60 km balances the needs of many users and provides warning times of up to similar to 20 s.