Seismic interferometry for mineral exploration: Passive seismic experiment over kylylahti mine area, Finland

We present the results of adapting seismic interferometry (SI) for reflection imaging in mineral exploration. We use a unique dataset of one-month ambient-noise recordings acquired with large-N array (~1000 receivers) deployed in a regular grid (50 m receiver interval, 200 m line interval) directly above the known mineralisation and underground mine infrastructure at the Kylylahti polymetallic mine located in Eastern Finland. Ambient-noise in the study area is dominated by the road traffic and mine activities (both surface and underground) providing quasi omni-directional distribution and broad freqeuncy spectrum of the noise sources. We start from the simple 2D forward modelling using existing geological model. Results of the SI applied to field data from selected receiver lines exhibit reflections related to the bottom of the ore body as well as the reflection from the target area confirmed by synthetics. Finally, we develop robust mineral exploration SI workflow (MESI) tailored for reflection imaging and apply it to our 3D ambient-noise dataset. Migrated sections obtained from the MESI-processed data exhibit high reflectivity, compatible with the active-source seismics and directly related to the known geological structures.