Passive Seismic Imaging of the Orthomagmatic Ore Deposits Using Regional Earthquake Interferometry: A Case Study of the Akanvaara V-Cr-PGE Deposit in Northern Finland

Why It Matters

This technique provides a low‑cost, high‑resolution alternative to active seismic methods, accelerating discovery of critical raw materials. Its ability to uncover hidden structures improves targeting and reduces exploration risk.

Key Takeaways

• Pn‑coda interferometry converts ambient noise into virtual sources.
• 771 three‑component sensors recorded high‑resolution data.
• Identified known and previously unknown deposit structures.
• Method works for both greenfield and brownfield exploration.
• Cost‑effective alternative to traditional active seismic surveys.

Pulse Analysis

The global push for critical raw materials such as vanadium, chromium, and platinum‑group elements has intensified the search for more efficient exploration tools. Traditional active‑source seismic surveys, while detailed, demand substantial logistical effort and expense, especially in rugged, hard‑rock environments. Passive seismic imaging, which exploits ambient seismic energy, offers a compelling alternative by turning background vibrations into useful signals. By harnessing regional earthquake coda, researchers can probe subsurface structures without generating artificial waves, aligning with sustainability goals and tighter project budgets.

The new method focuses on the Pn‑wave coda, the surface‑reflected portion of teleseismic body waves that travels along the crust‑mantle boundary. Through interferometric processing, the recorded coda is transformed into an empirical Green’s tensor, effectively simulating a virtual source at any chosen location. This tensor captures reflected and converted body‑wave arrivals that map elastic contrasts across geological interfaces. In the Akanvaara study, a dense array of 771 three‑component sensors recorded high‑resolution data, enabling the detection of subtle wave conversions that would be invisible to conventional techniques.

Results from the Finnish ultramafic intrusion revealed not only the expected lithological boundaries but also previously undocumented fault zones and mineralized lenses, underscoring the method’s sensitivity. Because the workflow relies on existing regional seismicity, exploration teams can deploy it quickly in both greenfield prospects and brownfield extensions, reducing upfront costs and environmental impact. As the mining sector seeks faster, greener pathways to locate critical minerals, passive Pn‑coda interferometry is poised to become a standard component of the exploration toolbox, complementing geophysical and geological models.