Evidence for a fluid flow triggered spatio-temporal migration of seismicity in the 2001 Mw 7.7 Bhuj earthquake region, Gujarat, India, during 2001–2013

Abstract

We studied the variations in spatial and temporal clustering of earthquake activity (during 2001-2013) in the Kachchh seismic zone, Gujarat, India, by precisely relocating 3478 events using a joint hypocentral determination (JHD) relocation technique, and high-quality arrival times of 21032 P-and 20870 S-waves. Temporal disposition of estimated station corrections of P-and S-waves suggests that the fluid flow in the causative fault zone of the 2001 Bhuj mainshock increased during 2001-2010, while it reduced during 2011-2013, due to the healing process associated with the perturbed Kachchh fault zone. We also estimated the isotropic seismic diffusivities from epicentral growth patterns, which are found to be much lower than those observed for reservoir-induced seismicity sites in the world. Finally, we analysed the spatial and temporal evolution of this earthquake sequence by solving the diffusion equation of pore-pressure relaxation caused by co-and post-seismic stress changes associated with earthquakes. The value of the isotropic diffusivity is estimated to be 100 m 2 /s for the Kachchh rift zone. This gives a higher permeability (after a lapse time of 14 years from the occurrence of the 2001 Bhuj mainshock) in comparison to those observed for other intraplate regions in the world. Our results suggest that the observed spatio-temporal migration of seismicity is consistent with the shallow (meteoric water circulation at 0-10 km depths) and deeper (metamorphic fluid and volatile CO 2 circulation at 10-40 km depths) fluid flows in the permeable and fractured causative fault zone of the 2001 Bhuj earthquake.

Constitutive Law for Earthquake Production Based on Rate‐and‐State Friction: Theory and Application of Interacting Sources

“…The Dieterich model, either modified or original, does not decay with time, whereas the interaction model spreads out and decays in a qualitatively similar manner to a diffusion process. Indeed, long sustained aftershock sequences have been observed for intraplate earthquakes that have shown space‐time characteristics similar to a diffusion process (Mandal et al, ).…”