Fluid-Rock Mechanical Interaction with Applications for Inducing and Triggering Earthquakes

Session: Mechanisms of Induced Seismicity: Pressure Diffusion, Elastic Stressing and Aseismic Slip
Type: Oral
Date: 4/29/2020
Time: 10:45 AM
Room: 215 + 220
Description: 

The interaction between crustal fluids and faults has been widely documented. Fluids can perturb the stress near faults, enhancing earthquake occurrence. Although the underlying mechanisms are well understood, more efforts are needed to answer why, how, when and where induced earthquakes occur. In the Central and Eastern US., a dramatic increase of seismicity since 2008 can be attributed to high-volume deep wastewater injection. Integrating injection, seismic and hydrogeological data through a physics-based framework accounting for poroelastic coupling and rate-and-state earthquake nucleation, we build models to quantitatively link injection and seismic hazard. We study injection-induced seismicity in Texas, Oklahoma and Kansas. The results collectively show that (1) Induced earthquake magnitude-time distribution is reproducible using our physics-based model. (2) Both pore pressure and poroelastic stresses correlate with injection-induced seismicity, however, pore pressure is the primary driver, which is enhanced by poroelastic stresses (e.g., in Oklahoma). (3) A reservoir’s hydrogeological heterogeneity and background stress state are important factors for assessing seismic hazard at the regional scale. (4) The far-reaching effect of fluid injection should be considered for local seismic hazard assessment. Moreover, fluid extraction can also cause earthquakes. Poroelastic stresses are mostly invoked to explain earthquake triggering outside the depleting reservoir. However, such poroelastic stresses can also cause pore pressure increase under undrained conditions (Noordbergum effect). Thus, both pore pressure and poroelastic stresses should be examined to evaluate the link between earthquakes and extraction. Here, we examine extraction, seismic and geodetic data from the COSO and Leyte geothermal fields and present preliminary model results indicating a mechanical interaction with the nearby 2019 Ridgecrest and 2017 Leyte earthquakes, respectively. These results confirm that fluid extraction under certain hydrogeological conditions can promote earthquakes.

Presenting Author: Guang Zhai

Authors