b'Education matters Evidence from the Nile Delta places thetopography signal from the Afar Plumecontent and Ore grade deposit models. rivers age at over 30 Ma, implying thatand a strong negative signal associatedHigh Tau values appear to correlate in its genesis may be intricately linked withwith Tethyan subduction, produced theareas of high Ni-Cu contents and high the eruption of the massive Ethiopianbest match with the real-world Nile RiverOre grade. Low Tau occur in the absence Plateau flood basalts at this time. Theand Delta, and is therefore consideredof Ore. The choice of vertical or horizontal longevity of the Nile, which persistedto be the preferred dynamic topographytransmitter configuration affects the through such events as the openingscenario for this region. coupling, and subtle difference in Tau of the Red Sea and the aridification ofFionnuala Campbell, Curtin University:values are observed. the Sahara Desert, may be explainedComparison, evaluation, and optimisationThis research demonstrates the by the existence of a long-lived, large- of the near surface Loupe TEM system forsuccessful application of the Loupe EM scale mantle convection cell beneathunderground nickel sulphide detection system for conductivity mapping in northern Africa. This convection cell wasboth hydro-geological applications, and responsible for a persistent downwardConventional transient electromagneticunderground mine environments.dynamic topographic gradient betweenmethods are limited by substantial the Afar Plume beneath the Ethiopianmobilisation requirements, longBodee Bignell, University of Queensland: Plateau and the Tethys slab in the easterncollection times and large footprints,Analysis of teleseismic earthquake Mediterranean since at least 40 Ma. making them impractical for shallowrecordings on nodal seismic sensorsIn this work, the influence of dynamicconductivity investigations and used topographyamong other factors in dense vegetation, enclosed or urban on the evolution of the Nile River wasenvironments.investigated, using the open-sourceThe applications of portable EM systems Badlands surface processes modellingare expanding, ranging from mineral software package (https://badlands. exploration and hydrogeological readthedocs.io). Badlands simulates theinvestigations, to shallow geotechnical erosion, transport, and deposition ofand archaeological survey applications. sediments in a self-consistent manner,The Loupe EM system is a portable allowing the interrogation of spatialtime domain electromagnetic system, and temporal patterns of sedimentdesigned for rapid data collection in erosion and deposition, river catchmenta variety of applications. The primary morphologies, and stratigraphicresearch objective is to determine the structures. A range of forcing conditionsapplicability of this system and compare were incorporated into the Badlandsthe Loupe EM system with electrical models, including paleoclimate, spatiallyconductivity measurements. This research variable lithology and thus erodibility,presents two major case studies within and three-dimensional motionslogistically challenging environments associated with both tectonic activityincluded saltwater interface mapping and dynamic topography. at Woodman Point, Cockburn, Western Model results were evaluated byAustralia and the Nova UndergroundIn the past few years, nodal sensors comparison to real-world sedimentationMine site (IGO Limited) located in thehave emerged as the default for seismic maps and cross-sections derived fromFraser Range, Western Australia. exploration. These systems record seismic data, in addition to the present- In April 2020 over 3.5 km of Loupe EMcontinuously, and hence record a range day morphology of the Nile Riverdata was acquired at Woodman Point inof passive events. We have examined catchment. Sequence stratigraphicapproximately 1 hour. Inversion modelsdata from a number of such surveys in analyses were also performed onfor the Loupe EM data were created andQueenslands Bowen Basin. Although the modelled Nile Delta in ordercompared to Coogee 1A and Coogeethe sensor is designed for higher-to investigate the possible relative1B induction well logs, NanoTEM andfrequency events, with appropriate contributions of various factors to theERI inversion models. The Loupe EMpre-processing it is possible to extract stratigraphic structure of the region.system showed promising results inhigh quality records of teleseismic This marks one of the first instances ofmapping the geometry of the electrically(distant) earthquakes which are of sequence stratigraphy being applied toconductive saline water wedge andpotential interest in analysis of the crust the results of a self-consistent, realistic (asdelineating the high conductive layerand upper mantle near the receivers. opposed to generic) numerical model. at depths of approximately 25 m. SmallAspects of the pre-processing are Two different dynamic topography(5 m) transmitter-receiver separationsof interest. Cross-correlations of the scenarios for the region, derived fromhighlighted the saline water wedge,earthquake P-wave reveal inter-node geodynamic models, were tested. Thesewhile larger separations (12 m) resolvedtime variations which resemble statics two geodynamic models differ mostthe impermeable high conductivity layercontours from conventional reflection significantly in the presence or absenceat depth. processing. Examination of time-distance of a well-defined Afar Plume beneathThe Loupe EM data was collected by IGOvariation across the survey area provides the Ethiopian Plateau. A third scenario,Limited at the Nova Underground Nickelan estimate of apparent slowness of the incorporating elements from both of theSulphide mine along two mine drivearriving P-wave, useful for confirmation geodynamic models, was also developed.levels in September 2020. Time constantsof theoretical travel-time models.This hybrid scenario, which includedwere calculated for the Loupe EMBecause of the large channel counts in both a distinctive positive dynamicmeasurements and compared to Ni-Cumodern surveys, stacking the teleseismic DECEMBER 2020 PREVIEW 38'