Advanced non-invasive geophysical monitoring techniques

Geophysical methods can be used to create images of the Earth’s interior that
constitute snapshots at the moment of data acquisition. In many applications,
it is important to measure the temporal change in the subsurface, because
the change is associated with deformation, fluid flow, temperature changes,
or changes in material properties. We present an overview how noninvasive
geophysical methods can be used for this purpose. We focus on monitoring mechanical
properties, fluid transport, and biogeochemical processes, and present
case studies that illustrate the use of geophysical method for detecting timelapse
changes in associated properties. The examples include: measuring uplift
of the Earth’s surface, compaction near a producing hydrocarbon reservoir, the
seismic detection of stress changes, monitoring buildings, the detection of fluid
flow along a fault zone, electrical monitoring of fluid infiltration and redox potential,
and electrical and seismic monitoring of microbially mediated processes.
An overlying research question in geophysical monitoring concerns the use of
these time-lapse changes, notably the assesment of uncertainty, the combination
of disparate data, and the interface with those who make decisions based on
time-lapse information.