Fiber-Optic Array Mapped Utah Microearthquakes

A new borehole sensing method captured seismic data at 2-meter resolution to improve subsurface hazard assessments.

Updated on Oct. 6, 2026 in Geology

Isometric editorial illustration of a fiber-optic cable running through horizontal subterranean rock layers, representing subsurface geological monitoring. — Researchers at the Cape Modern geothermal site in Utah successfully demonstrated a fiber-optic borehole sensing array to map deep-seated microearthquake activity. AI Illustration. Upload story photo >

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In 2026, researchers demonstrated a fiber-optic distributed acoustic sensing (DAS) array installed in a 3,000-meter-deep borehole at Utah's Cape Modern geothermal site. This system captured high-resolution seismic waves from thousands of microearthquakes to refine geologic monitoring.

Why it matters

Detecting microearthquakes is often difficult due to rapid energy dissipation in the crust, limiting the precision of traditional seismic hazard models. This study provides a more sensitive measurement technique that reveals seismic properties otherwise obscured at shallower depths.

The array utilized 1,600 stations spaced 2 meters apart within a 3,000-meter-deep borehole. Data showed that high attenuation, or energy loss, occurred near the surface and consistently decreased with depth, while spectral stress drop proved independent of earthquake magnitude.

The details

Distributed acoustic sensing works by detecting small variations in light reflected back through standard fiber-optic cables when they are subjected to mechanical vibration. Researchers analyzed the strain along the fiber to track seismic waves as they propagated through the subsurface. By placing the sensor array deep underground, the team effectively bypassed high levels of surface-related noise to isolate signals from smaller, deep-seated microearthquakes.

2026: The study was published in the peer-reviewed journal.

The Tech Race

This deployment marks a shift toward high-density fiber-optic monitoring in geothermal environments, moving beyond the capabilities of traditional surface-level geophones. The research establishes a new performance baseline for borehole-based seismic acquisition in complex underground settings.

This research provides a more precise framework for assessing subsurface activity, which could eventually inform site-specific hazard assessments for geothermal energy infrastructure in Utah. The current findings serve as a technical validation for future operators to better distinguish seismic signals from environmental noise.

The takeaway

The study demonstrates that deep-borehole fiber arrays significantly improve our ability to resolve microseismic events. Future efforts will likely focus on normalizing these measurements against specific gauge lengths and cable orientations to standardize the sensing technique.