Undrained fault-zone poroelastic feedback enables the 2011 Prague earthquake cascade

Zhengze Li , Sylvain Barbot

Subsurface fluid injection supports wastewater disposal, geothermal energy, and geological storage but can trigger damaging earthquakes. Predicting whether an injection-triggered rupture stops or spreads across multiple faults remains challenging. In the 2011 Prague, Oklahoma, sequence, the mechanism enabling rupture transfer to the fault hosting the third large earthquake has remained unresolved. Here we build an observation-constrained model linking pore-pressure diffusion, frictional fault slip, elastic stress interactions, and a local undrained fault-zone poroelastic response. The model reproduces nearly 18 years of hydraulic buildup and the complete three-event sequence. Rupture of the second fault loads the third fault favorably in shear but also increases normal compression that inhibits slip. In our simulations, favorable shear loading develops into dynamic rupture on the third fault only when undrained fault-zone poroelastic feedback offsets enough of the opposing clamping. Hydraulic properties shape the timing and location of rupture initiation, and greater source–fault separation substantially delays it. After rupture begins, network prestress, geometry, and elastic interactions increasingly determine whether rupture spreads and which faults participate. These results reveal two-way hydromechanical coupling in induced-earthquake sequences: injection governs hydraulic preparation, while rupture-induced stress changes feed back on fault-zone pore pressure and subsequent fault stability.