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- Title
The PLUM Earthquake Early Warning Algorithm: A Retrospective Case Study of West Coast, USA, Data.
- Authors
Kilb, D.; Bunn, J. J.; Saunders, J. K.; Cochran, E. S.; Minson, S. E.; Baltay, A.; O'Rourke, C. T.; Hoshiba, M.; Kodera, Y.
- Abstract
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 (IMMI) using velocity and acceleration data, leveraging co‐located sensors to avoid problematic signals. An event detection is issued when the observed IMMI exceeds a given threshold(s). We find a two‐station detection method using IMMI 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 IMMI 4+ shaking from local earthquakes and could complement and enhance EEW in the U.S. Plain Language Summary: Earthquake early warning (EEW) detection schemes require (1) ample seismic information to identify where large ground motions are underway; (2) determining if these ground motions are significant enough to issue a detection; and (3) detecting large ground motions in a timely fashion. Some EEW methods estimate earthquake source parameters like magnitude and location and then input those parameters into a ground‐motion prediction equation, while other methods use observations of the ground motions to directly forecast shaking. We explore the latter approach using the PLUM (Propagation of Local Undamped Motion) method to detect earthquakes that produce shaking above a target value. In this work, we test PLUM's ability to detect earthquakes using two data sets: 558 earthquakes magnitude 3.5 and above from California, Oregon, and Washington (2012–2017) and a test suite of historic and problematic signals (1999–2015) curated by ShakeAlert. We find a two‐station detection method is preferred over a one‐station method as two‐stations can greatly minimize false detections. The PLUM method is also 100% successful at avoiding non‐earthquake anomalous signals and can successfully differentiate ground shaking from local and distant earthquakes. We conclude that PLUM may be a promising candidate for integration into the U.S. EEW system. Key Points: Propagation of Local Undamped Motion (PLUM) detects offshore events that produce at least moderate onshore ground motions, including an event problematic for other algorithmsPLUM's detection times are as timely, and sometimes faster, than other earthquake early warning detection timesPLUM correctly avoids erroneous detections for all teleseismic, calibration pulses, and anomalous signals in the test suite
- Subjects
UNITED States; EARTHQUAKE prediction; SEISMIC event location; SEISMOLOGICAL research; EARTHQUAKE intensity; EARTHQUAKE magnitude; EARTHQUAKES
- Publication
Journal of Geophysical Research. Solid Earth, 2021, Vol 126, Issue 7, p1
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2020JB021053