Wastewater disposal and earthquake swarm activity at the southern end of the Central Valley, California,

T.H.W. Goebel (1) , S.M. Hosseini (2) , F. Cappa (3, 4) , E. Hauksson (5) , J.-P. Ampuero (5) , F. Aminzadeh (2) , J.B. Saleeby (2)

1 Department of Earth and Planetary Sciences [Santa Cruz]
2 UCLA - University of California [Los Angeles]
3 IUF - Institut universitaire de France
4 GEOAZUR 7329 - Géoazur
5 Division of Geological and Planetary Sciences [Pasadena]

Fracture and fault zones can channel fluid flow and transmit injection-induced pore pressure changes over large distances (>km), at which seismicity is rarely suspected to be human induced. We use seismicity analysis and hydrogeological models to examine the role of seismically active faults in inducing earthquakes. We analyze a potentially injection-induced earthquake swarm with three events above M4 near the White Wolf fault (WWF). The swarm deviates from classic main aftershock behavior, exhibiting uncharacteristically low Gutenberg-Richter b of 0.6, and systematic migration patterns. Some smaller events occurred southeast of the WWF in an area of several disposal wells, one of which became active just 5 months before the main swarm activity. Hydrogeological modeling revealed that wastewater disposal likely contributed to seismicity via localized pressure increase along a seismically active fault. Our results suggest that induced seismicity may remain undetected in California without detailed analysis of local geologic setting, seismicity, and fluid diffusion.

Domaines: Sciences de la Terre

T.H.W. Goebel, S.M. Hosseini, F. Cappa, E. Hauksson, J.-P. Ampuero, et al.. Wastewater disposal and earthquake swarm activity at the southern end of the Central Valley, California,. Geophysical Research Letters, 2016, 43 (3), pp.1092-1099. ⟨10.1002/2015GL066948⟩. ⟨hal-01346818⟩