Time-lapse geophysical monitoring and inversion are valuable tools in
hydrogeology for monitoring changes in the subsurface due to natural and
forced (tracer) dynamics. However, the resulting models may suffer from
insufficient resolution, which leads to underestimated variability and
poor mass recovery. Structural joint inversion using cross-gradient
constraints can provide higher-resolution models compared with
individual inversions and we present the first application to time-lapse
data. The results from a synthetic and field vadose zone water tracer
injection experiment show that joint 3-D time-lapse inversion of
crosshole electrical resistance tomography (ERT) and ground penetrating
radar (GPR) traveltime data significantly improve the imaged
characteristics of the point injected plume, such as lateral spreading
and center of mass, as well as the overall consistency between models.
The joint inversion method appears to work well for cases when one
hydrological state variable (in this case moisture content) controls the
time-lapse response of both geophysical methods. Citation: Doetsch, J.,
N. Linde, and A. Binley (2010), Structural joint inversion of time-lapse
crosshole ERT and GPR traveltime data, Geophys. Res. Lett., 37, L24404,
doi: 10.1029/2010GL045482.