Abstract:
This study provides a deep understanding of the complex interaction between thermo-hydro-mechanical behaviours and earthquake rupture process in injection induced earthquake areas with a coupled numerical model. The physics based numerical modelling specially designed for injection induced seismicity integrates fluid flow, heat transfer, mechanical deformation and seismic rupture sequences. The applicability of the hydro-mechanical and thermo-hydro-mechanical coupled earthquake sequence numerical models is examined with a variety of scenarios which vary injection rate, fault strike direction and injection fluid temperature. The simulation results demonstrate the effect of each parameter on the injection induced micro-earthquake activity. As a case study of applying the developed seismic sequence model, focal mechanism research and earthquake cluster analysis reveal the characteristics of the Wairakei fracture geometries. The seismogenic hydraulic and mechanical properties of the Karapiti formations and fractures are also identified using a triggering front method and the Karapiti 1D P-wave velocity model analysis. The hydro-mechanical coupled seismicity rate prediction model is finally applied to the Karapiti re-injection area to investigate the relationship between the injection well operation and injection induced micro-seismicity sequences. The reproduced spatiotemporal seismicity rate is in broad agreement with the observed earthquakes in the Karapiti active seismic zone.
