View article

We present a physics-based monitoring tool for four-dimensional pore pressure variations, using seismic ambient noise. We use passive image interferometry to retrieve surface-wave velocity changes as a function of frequency. We show that surface-wave velocity changes can directly be linked to depth variations of pore pressure change through sensitivity kernels. We demonstrate that these kernels can be used to invert observations of seismic velocity changes into hydrological pore pressure variations as a function of time, depth and region. In Groningen, the Netherlands, most sensitivity to pore pressure variations is in the shallowest 200 m of the subsurface due to the frequency band for which seismic velocity measurements are possible.