Dr. Joseph Doetsch - Vortrag am 18.02.2019Urheberrecht: Doetsch
Monday, 18 February 2019 at 4:15 pm in room 217
Dr. Joseph Doetsch
Grimsel Project Manager, ETH Zürich:
Subsurface Fluid Pressure and Rock Deformation Monitoring
Using Seismic Velocity Observations
Fluid pressure within the Earth’s crust is a key driver for triggering natural and human-induced seismicity. Measuring fluid pressure evolution would be highly beneficial for understanding the underlying driving mechanisms and supporting seismic hazard assessment. In this presentation, I will show that seismic velocities monitored on the 20-m scale respond directly to changes in fluid pressure. Our data show that volumetric strain resulting from effective stress changes is sensed by seismic velocity, while shear dislocation is not. We are able to calibrate seismic velocity evolution against fluid pressure and strain with in situ measurements during a decameter-scale fluid injection experiment in crystalline rock. Thus, our 4-D seismic tomograms enable tracking of fluid pressure and strain evolution. Our findings demonstrate a strong potential toward monitoring transient fluid pressure variations and stress changes for well-instrumented field sites and could be extended to monitoring hydraulic stimulations in deep reservoirs.