Bailey, E, Yanagimura, Y, Martyniuk, E, Collins, D & Angus, D 2026, 'Timelapse passive seismic tomography at New Afton C-Zone mine', in A van As, D Cumming-Potvin & J Wesseloo (eds), Caving 2026: Proceedings of the Sixth International Conference on Block and Sublevel Caving, Australian Centre for Geomechanics, Perth, pp. 1-13, https://doi.org/10.36487/ACG_repo/2645_62 (https://papers.acg.uwa.edu.au/p/2645_62_Bailey/) Abstract: Passive seismic travel-time tomography is an effective tool for monitoring the initiation and progression of cave growth and tracking the evolution of the stress field of the rock mass. This information is valuable for ground control engineering to better understand how the rock mass is behaving as the cave propagates and identify areas of high stress for risk mitigation. Travel-time tomography maps changes in the P-wave and Swave travel times to calculate changes in the spatial distribution of P-wave and S-wave velocities. Compared to active source tomography, passive seismic tomography has the benefit of using existing seismic activity to characterise and improve imaging of a subsurface rock body if sufficient ray path coverage exists from source to sensor. Seismic attenuation tomography is an extension of passive seismic body-wave tomographic analysis that maps changes in attenuation of the higher frequency components of the P-waves and S-waves. Greater attenuation can be interpreted as increased rock damage or the reduction of stress leading to fracture opening. In this analysis, events and blasts were both used to generate velocity and attenuation tomography results. These are presented and compared to seismicity at monthly intervals for the ongoing development of the New Afton C-Zone cave from undercut blasting to cave initiation and caving propagation. These results are presented alongside and validated by Geo4Sight estimates of the cave shape.