Analyzing Seismic and Acoustic Signals with Network-Based Coherence and Phase

Abstract

The seismoacoustic wavefield contains a variety of signals that can be challenging to detect and characterize, particularly those that are weak, emergent, or visible only on a subset of stations. A few examples of such sources include volcanic and tectonic tremor, anthropogenic noise, landslides, and glaciers. Here, we present network-based coherence—a simple cross-spectral method applicable to both seismic and acoustic sensors in network or array configurations. The method enhances signals that are coherent across multiple stations while suppressing noise unique to individual sensors, enabling robust detection of subtle seismoacoustic sources. Building on this, we introduce a phase-based acoustic source localization method that uses interstation phase differences to locate non-impulsive signals. We demonstrate these methods on data from an operational volcano seismic network and an International Monitoring System infrasound array. At Mount Spurr, Alaska, seismic network coherence reveals weak, ephemeral tremor during a period of unrest in 2024–2025. At the infrasound array I53US, array coherence identifies monochromatic and frequency-gliding noise sources, and phase-based location attributes a persistent ∼2 Hz signal to a nearby power plant. We envision this approach as a tool for data quality control, volcano monitoring, and noise assessment across seismic or acoustic networks and arrays.