Geophysical methods are useful
non-invasive means of collecting subsurface information on the environmental
impacts of resource developments. Techniques such as seismic refraction, ground
probing radar and magnetics are well established tools for environmental studies
of waste disposal sites. Repeat resistivity surveys, gravity surveys, and
infrared or multispectral remote sensing hold great promise for monitoring
environmental changes. Examples from
New
Zealand
include geothermal field monitoring, which may involve the use of geophysics for
.detecting changes of surface thermal activity, hydrothermal eruptions, induced
earthquakes, contamination or depletion of shallow groundwater, and subsurface
fluid recharge. Other examples include resistivity monitoring of contained
effluent disposal ponds, tailings dams and landfills. Experience has shown that
care is necessary to identify the natural variability of the parameter measured
before drawing conclusions regarding an observed
change.