This study introduces a technique for four-dimensional pore pressure
monitoring using passive image interferometry. Surface-wave velocity
changes as a function of frequency are directly linked to depth
variations of pore pressure changes through sensitivity kernels. We
demonstrate that these kernels can be used to invert time-lapse seismic
velocity changes, retrieved with passive image interferometry, for
hydrological pore pressure variations as a function of time, depth and
region. This new approach is applied in the Groningen region of the
Netherlands. We show good recovery of pore pressure variations in the
upper 200 m of the subsurface from passive seismic velocity
observations. This depth range is primarily limited by the reliable
frequency range of the seismic data.