← Back to Gallery

Session: Real-Time Monitoring and Warning with Fiber Optic Seismology [Poster]

Type: Poster

Date: 10/7/2024

Time: 05:00 PM

Room: Stanley Park Ballroom

Assessing Distributed Acoustic Sensing Strain-Rate Waveform Statistics for Improving Earthquake Early Warning

DAS seismology offers new opportunities for earthquake early warning (EEW) as existing “dark fibers” are used as dense linear arrays of strain meters. Here, we examine the statistical features of DAS measurements of the first few seconds after P-wave arrivals from small-to-moderate local earthquakes for applications to EEW. Our data are from a 15-km long fiber onshore between Arcata and Eureka near the Mendocino Triple Junction in Northern California, where a M6.4 occurred about 30 km away, near Ferndale, on December 20, 2022. We analyze 5 months of local seismicity following the 2022 Ferndale event, including 12 M>4 events and one M5.4 on January 1, 2023. We calculate DAS waveform statistics before and after P-wave arrivals for the purpose of designing a DAS-based “tripwire” alert mechanism for EEW for nearby large earthquakes, thus expanding EEW coverage wherever dark fibers are available. We identify 70 two-minute-long DAS records of local earthquakes using the Comcat event catalog and an automatic phase picker (PhaseNet-DAS; Zhu et al., 2023), and analyze their statistical features in both time and frequency domains in the ten seconds before and four seconds after a P wave is detected across a spatial segment of the fiber. We find that some features correlate with catalog magnitude including continuous wavelet transform coefficients, short-term average/long-term average (STA/LTA) ratios, and strain-rate amplitudes, and are largely independent of distance and azimuth. We suggest that near-field terms which are thought to be characteristic of large, but not small, rupture processes, may help broadly distinguish between large and small earthquakes on DAS fibers, thus improving our ability to characterize potentially hazardous earthquakes in a timely and effective manner.

Presenting Author: Theresa

Additional Authors