b'AEGC 2021Short abstractswhich characterise the granite-greenstone association. In thisassociated with each source body, or source edge. Further, study, 2D seismic sections have been used for constrainingthe relative sizes of these highs and lows varies depending on the location of rock unit boundaries being solved during thethe magnetic latitude or inclination of the Earths field. There 3D gravity geometric inversion. The proposed work is the firstare two common methods of dealing with this issue, one is we know of that proposes a 3D level-set inversion consideringto mathematically transform the data to what it would be if different geophysical datasets with different spatial coverage.the survey were at the magnetic pole, but this process can be In the proposed method, the utilisation of seismic data resultsunstable at low magnetic latitudes or the transformation is of in a reduction of the ill-posedness of the gravity inversionlittle value if remanent magnetization adds a dipolar anomaly problem by creating a model consistent with images providedthat is not in the assumed direction. The second method is by sparse seismic sections. It also allows interpolating seismicto transform the data to the analytic-signal amplitude (ASA), information away from the 2D lines consistently with gravitywhich creates a monopolar feature for each body (or edge) measurements. and the shape of the feature is independent of remanent magnetization in any direction. However, the ASA anomaly In many hard-rock geoscientific investigations, seismic datacan appear broader than the total-field anomaly, so features is sparse and our results indicate that unit boundaries fromsometimes merge together on map views. It is possible to gravity inversion can be very well constrained with seismicfurther transform the ASA to the total field of a body that is sections sparsely distributed within the model. Thus, weat the pole and has a vertical dip, using an appropriate local conclude that it has the potential to bring the state of thephase or tilt angle. The transformation is exact for contacts art a step further towards building a 3D geological modelwhen calculated from the first-order ASA (calculated from incorporating several sources of information in similar regionsthe vertical and horizontal derivatives), but there are issues of investigation. with the sign of the transformed data depending on whether you are over one edge or the other edge of a discrete source 91: Australian geomagnetic observatory networkbody. However, an approximate transformation of the zeroth-monitors space weather hazard180 years on order ASA does not have this issue and gives good results on synthetic data if the noise in the local phase is handled Dr Liejun Wang 1, Mr Andrew Lewis1, Mr Bill Jones1, Mr Jingmingappropriately. The resulting maps outline the magnetic source Duan2, Dr Adrian Hitchman1 and Mr Matthew Gard1 bodies and have amplitudes proportional to the magnetic susceptibility.1 Geoscience Australia2 Mineral Systems Branch, Geoscience Australia 99: The role of passive seismic imaging in near-mine Geoscience Australias geomagnetic observatory networkexplorationcovers one-eighth of the Earth. The first Australian geomagneticDr Gerrit Olivier , Mr Andrew Foley , Miss Nicola Ramm , Dr observatory was established in 1840 in Hobart. This almost1 2 3continuous 180 year period of magnetic-field monitoringPhilippe Dales3, Dr Martin Gal3, Mr Tjaart de Wit3,4, Mr Francois provides an invaluable dataset for scientific research. Malan and Mr Olaf Goldbach3Geomagnetic storms induce electric currents in power lines,1 Institute of Mine Seismology, University of Tasmania, GSA, causing instabilities and sometimes blackouts in electricityASEGtransmission systems. Power outages to business, financial2 Gold Fieldsand industrial centres cause major disruption and potentially3 Institute of Mine Seismologybillions of dollars of economic losses. The intensity of4 Colorado School of Minesgeomagnetically induced currents is closely associated withThe future of the mineral mining industry relies on the geological structure. ongoing success of exploration projects. In this paper, Geomagnetic storm events across three decades have beenthe use of near-mine passive seismic imaging is discussed analysed to develop a statistical model of geomagnetic stormas a solution to exploration demands. We explore the activity in Australia and the model used to predict the intensityissues currently being faced by mines worldwide and the of geomagnetically induced currents (GICs) in Australiasadvances in technology that have led to an increase in modern-day power grids. Modelling shows the induced electricpassive seismic imaging abilities. Traditional shortcomings fields in South Australia and Victoria caused by an intensewith passive seismic imaging are presented, along with magnetic storm in 1989. Real-time forecasting of geomagneticproposed solutions by utilising these methods specifically hazards using Geoscience Australias geomagnetic observatoryin a near-mine environment. We performed a multi-scale network and AusLAMP magnetotelluric data helps developimaging experiment at an underground gold mine in Western national strategies and risk assessment procedures to mitigateAustralia. Here we installed a dense, temporary surface space weather hazard. geophone array and used these stations in conjunction with an existing permanent in-mine seismic array to produce high resolution images adjacent to and below the existing 95: Transformative geophysics: Alternatives to themine. Ambient noise surface wave tomography, reflection reduction-to-pole transformation of magnetic data seismic and travel time tomography were applied to both the surface and in-mine arrays. The resulting images were used to Prof Richard Smith 1 delineate the orebody near the existing mining infrastructure 1 Laurentian University and to identify drilling targets below and adjacent to the current mine. We show that passive seismic methods have the Magnetic data is difficult to interpret due to the bipolarpotential to reduce the amount of drilling needed for mineral nature of the anomalies, as there is generally a high and a lowdeposit detection and delineation.77 PREVIEW AUGUST 2021'