Noise-based monitoring and imaging of aseismic transient deformation induced by the 2006 Basel reservoir stimulation

ABSTRACTWe have analyzed the time-dependent properties of the ambient seismic wavefield between 0.1 and 8 Hz to detect, resolve, monitor, and image the deformation induced by the water injection associated with the stimulation of the 2006 Deep Heat Mining Project in the city of Basel, Switzerland. The application of passive methods allowed the detection of an aseismic transient of approximately 35 days’ duration that began with the onset of the reservoir stimulation. Peak deformation was reached some 15 days after the bleed-off and after the induced seismicity ceased. We resolved a significant increase in seismic velocities and a simultaneous decorrelation of the noise correlation coda waveforms. The wavefield properties implied that the material response was monitored mainly in the sedimentary layer (<2.5  km) above the stimulated volume that was approximately 4.5 km deep. We inverted the velocity-change and decorrelation data to estimate the spatial distribution of the medium changes. The resulting imag...