Aftershocks driven by a high-pressure CO2 source at depth

Abstract

In northern Italy in 1997, two earthquakes of magnitudes 5.7 and 6 (separated by nine hours) marked the beginning of a sequence that lasted more than 30 days, with thousands of aftershocks including four additional events with magnitudes between 5 and 6. This normal-faulting sequence is not well explained with models of elastic stress transfer, particularly the persistence of hanging-wall seismicity that included two events with magnitudes greater than 5. Here we show that this sequence may have been driven by a fluid pressure pulse generated from the coseismic release of a known deep source of trapped high-pressure carbon dioxide (CO2). We find a strong correlation between the high-pressure front and the aftershock hypocentres over a two-week period, using precise hypocentre locations and a simple model of nonlinear diffusion. The triggering amplitude (10-20 MPa) of the pressure pulse overwhelms the typical (0.1-0.2 MPa) range from stress changes in the usual stress triggering models. We propose that aftershocks of large earthquakes in such geologic environments may be driven by the coseismic release of trapped, high-pressure fluids propagating through damaged zones created by the mainshock. This may provide a link between earthquakes, aftershocks, crust/mantle degassing and earthquake-triggered large-scale fluid flow.

Failure patterns caused by localized rise in pore‐fluid overpressure and effective strength of rocks

“…The main results are the following: (1) Depending on the initial conditions, the geometry, and the material properties, five different patterns of failure can be characterized, either with tensile or shear mode. (2) The critical fluid pressure at the onset of failure could also be determined for all failure patterns and an analytical solution for p c is given in equation (17) and Table 1. [26] These results can be used in many geological applications, including the formation of hydrothermal vent structures triggered by sill intrusion [Jamtveit et al, 2004], the aftershocks activities caused by motions of fluids inside faults [Miller et al, 2004], or the tremors caused by sediments dehydration in subduction zones [Shelly et al, 2006]. Finally, our simulations did not allow studying any transient effects in the fluid pressure during fracture propagation.…”

Shallow inland earthquakes in NE Japan possibly triggered by the 2011 off the Pacific coast of Tohoku Earthquake

“…This suggests that an inhomogeneous structure of viscoelastic structure and overpressured fluid distribution in the lower crust (e.g. Miller et al, 2004) are spatially related to the distribution of the post-megathrust events. Not only is the elastic stress transfer/change, but also are the inelastic deformation and/or fluid redistribution, possibly important for understanding the interaction between the large subduction-thrust ruptures and the ensuring inland earthquake.…”

Aftershock seismicity and tectonic setting of the 2015 September 16 Mw 8.3 Illapel earthquake, Central Chile

“…The reason for the spatial spreading of the aftershocks, compared to the coseismic rupture, may be due to the maximum differential stress changes in the region around the rupture area (Das & Henry 2003). According to poroelastic fluid diffusion models (Miller et al 2004;Terakawa et al 2013), the occurrence of earthquakes can drastically change the surrounding pore fluid pressure fields. Miller et al (2004) studied the 1997 Umbria-Marche seismic sequence in Italy, and proposed that aftershocks of large earthquakes may be driven by the coseismic release of trapped, highly pressurized fluids propagating through damage zones created during coseismic rupture.…”

“…According to poroelastic fluid diffusion models (Miller et al 2004;Terakawa et al 2013), the occurrence of earthquakes can drastically change the surrounding pore fluid pressure fields. Miller et al (2004) studied the 1997 Umbria-Marche seismic sequence in Italy, and proposed that aftershocks of large earthquakes may be driven by the coseismic release of trapped, highly pressurized fluids propagating through damage zones created during coseismic rupture. The associated pressure pulses are suggested to trigger aftershocks by reducing the effective normal stress of incipient slip at Bibliothek des Wissenschaftsparks Albert Einstein on September 29, 2016 http://gji.oxfordjournals.org/ Downloaded from applies.…”