Earthquake Location using Back Projection with Distributed Acoustic Sensing with Implications for Earthquake Early Warning

We present a back-projection based earthquake location method tailored to Distributed Acoustic Sensing (DAS) arrays, using short overlapping fiber segments and a combined P–S framework to reliably locate local earthquakes. A 66km quasi-linear telecommunication fiber in Israel was repurposed as a DAS array. We analyzed several local earthquakes with varying source–array geometries. We divided the fiber into overlapping 5.4 km segments and back-projected P- and S-wave strain-rate recordings using a local 1D velocity model over a regional grid of potential earthquake locations. Each grid point is assigned with P- and S-phase semblance, and the corresponding phase-specific origin times, associated with the timing of maximum semblance. Segment-specific P- and S-phase semblance maps and the difference between P and S origin times were combined through a weighting scheme that favors segments with spatially compact high-semblance regions. The objective is maximizing both P- and S-wave semblance and minimizing P- and S-wave origin time discrepancies. Results for the analyzed earthquakes reveal robust constraints on both azimuth and epicentral distance from the fiber, and demonstrate the ability to mitigate DAS-related artifacts associated with broadside sensitivity and reduced coherency. We demonstrated the potential of the approach for real-time earthquake location and showed its performance when only P-wave recordings are available, underscoring the method’s potential for future DAS-based earthquake early warning implementation.