Piezomagnetic effect of ground loading by Lake Gordon, Tasmania

A series of precisely repeated magnetic surveys has been carried out over a five year period, during the filling of Lake Gordon, Tasmania, following construction of a dam. After subtraction of the secular variation gradient over the region, a mean decrease of 1.6 nT in total field intensity is found over the survey area, which exceeds 600 km², corresponding to the expected form of a tectonomagnetic anomaly due to ground loading. During the survey period there were several local magnetic events, coinciding with more rapid, local changes in benchmark levels, that may be attributed to aseismic movements on faults in the area.