The Potential of Using Fiber Optic Distributed Acoustic Sensing (DAS) in Earthquake Early Warning Applications

Abstract

As the seismological community embraces fiber optic distributed acoustic sensing (DAS), DAS arrays are becoming a logical, scalable option to obtain strain and ground-motion data for which the installation of seismometers is not easy or cheap, such as in dense offshore arrays. The potential of strain data in earthquake early warning (EEW) applications has been recently demonstrated using records from borehole strainmeters (BSMs). However, current BSM networks are sparse, installing more BSMs is expensive and often impractical, and BSMs have the same limitations in offshore environments as other traditional seismic instruments. Here, we aim to provide a road map about how DAS data could be used in existing EEW applications, using the ShakeAlert EEW System for the West Coast of the United States as an example. We review the data requirements for EEW systems, examine ways in which strain-derived ground-motion data can be incorporated into such systems without significant modifications, and determine what is still needed for full utilization of DAS data in these applications. Importantly, EEW algorithms require ground-motion amplitude information for rapid earthquake source characterization; thus, accurate strain amplitude observations, not only phase information, are necessary for deriving these ground-motion metrics from DAS data. To obtain high-quality ground-motion observations, EEW-compatible DAS arrays need to be multicomponent, well coupled, and low noise. We suggest ways to achieve such data requirements using existing DAS technology and discuss areas in which further research is needed to optimize DAS array performance for EEW.

Fiber optic sensing for volcano monitoring and imaging volcanic processes

“…This was achieved using four fiber instances, each with 750 channels (Diaz-Mesa et al, 2023). Farghal et al (2022) discuss the potential of DDSS for early earthquake detection applications. Their conclusions can be transferred and adapted for volcano hazard assessment and improved monitoring, leading to more certain and timely alerts.…”

Assessing the Earthquake Recording Capability of an Ocean-bottom Distributed Acoustic Sensing Array in the Sanriku region, Japan

“…For nearshore experiments, some sensor arrays use cables to ensure their real-time and long-term data transmission to landing data centers (e.g., S-net in Japan or the US Ocean Observatories Initiative (OOI); Kanazawa et al, 2016;Delaney & Kelley, 2015). While these types of seafloor seismic observatories are important in mitigating earthquake-related hazards in active subduction zones (Hino et al, 2001;Baba et al, 2005;Farghal et al, 2022), their instrument density is still insufficient to provide detailed interpretation of marine environments and seismic wavefield.…”

An analysis of the dynamic range of Distributed Acoustic Sensing for Earthquake Early Warning

“…In recent years, Distributed Acoustic Sensing (DAS; Hartog, 2017) has been considered as a potential solution for improving EEW coverage, particularly in subduction settings (Zhan, 2020;Farghal et al, 2022;Lior et al, 2023;Yin et al, 2023a). DAS is a fibre-optic sensing technique that converts a fibre-optic (e.g., telecom) cable into an array of equidistant vibration sensors by means of optical interferometry.…”