Fleet's real-time ambient noise tomography service trialled at Northern Star's Kalgoorlie Operations

As mineral exploration extends deeper below surface, innovative geophysical techniques are necessary. In this paper we report on one of the first real-time field trials of Fleet Space Technologies' real-time ambient seismic noise tomography service, called ExoSphere, at Northern Star's Kalgoorlie Operations. During 45 days of acquisition, 40 Geode seismic sensors were deployed to survey roughly 80 km 2 to the north and south of the Fimiston gold mine, over eleven consecutive individual surveys. Acquisition was in near real-time, to a depth of 1km below surface. Due to the abundance of geological, geophysical and geotechnical data available in the study area, the trial uniquely showcases the applicability of the method to mineral exploration. The results of the trial indicate that the method is well suited to image the sub-vertical stratigraphy in Kalgoorlie in three dimensions, especially when acquired at an appropriate resolution. The challenges of applying the method are interpreting seismic velocities, which can vary significantly for the same rock type, and the non-unique nature of the inverse problem which requires robust parametrisation. The realtime application of ambient seismic noise tomography is a new geophysical tool available to mineral exploration companies to expedite the discovery of new deposits under cover, where traditional exploration methods struggle. The Kalgoorlie case study demonstrates the tremendous potential of the method, as an alternative to the more expensive and logistically challenging active seismic equivalent.