Mapping pressurized volcanic fluids from induced crustal seismic velocity drops

Abstract

Volcanic eruptions are caused by the release of pressure that has accumulated due to hot volcanic fluids at depth. Here, we show that the extent of the regions affected by pressurized fluids can be imaged through the measurement of their response to transient stress perturbations. We used records of seismic noise from the Japanese Hi-net seismic network to measure the crustal seismic velocity changes below volcanic regions caused by the 2011 moment magnitude (M(w)) 9.0 Tohoku-Oki earthquake. We interpret coseismic crustal seismic velocity reductions as related to the mechanical weakening of the pressurized crust by the dynamic stress associated with the seismic waves. We suggest, therefore, that mapping seismic velocity susceptibility to dynamic stress perturbations can be used for the imaging and characterization of volcanic systems.

Static and Dynamic Moduli of Malm Carbonate: A Poroelastic Correlation

“…However, when seismic energy is released, part of the energy propagates through the crust as seismic body waves resulting in dynamic stress changes, i.e. as transient stress perturbations (Brenguier et al, 2014). Due to the short time scale of an earthquake in comparison to the rate of fluid flow, undrained conditions are favored in the fluid saturated zones and a higher velocity ratio in comparison to drained conditions is expected.…”

“…There are some observations and evidence that confirm this hypothesis. For example, passivesource seismic imaging suggested the existence of a zone of high velocity and Poisson ratios down-dip of a subduction ridge which was attributed to high pore fluid pressures and low effective pressures (Brenguier et al, 2014). Moreover, Segall (1989) has shown that poroelastic contraction of a zone from which fluid are produced can destabilize faults and induce seismicity in areas where the fluid mass content does not change (i.e.…”

“…At the time of an earthquake the static stress change can be considered negligible (Brenguier et al, 2014). However, when seismic energy is released, part of the energy propagates through the crust as seismic body waves resulting in dynamic stress changes, i.e.…”

“…A novel method was developed to correlate the static and dynamic moduli, which can later be used to populate geomechanical models, to monitor the reservoir behavior using 4D seismic data, and for characterizing low effective pressure zones after earthquakes (Segall, 1989;Brenguier et al, 2014). In other words, this correlation approach can be used in relating seismicity and geomechanics (seismo-mechanics).…”

Monitoring deep‐ocean temperatures using acoustic ambient noise

“…This has been shown among others in the fields of ultrasonics [Weaver and Lobkis, 2001;Larose et al, 2004;Lani et al, 2011], helioseismology [Duvall et al, 1993;Rickett and Claerbout, 1996], seismology [Sabra et al, 2005a;Shapiro et al, 2005;Brenguier et al, 2007], structural health monitoring [Sabra and Huston, 2011;Snieder and Cafak, 2006;Larose et al, 2007;Farrar and James, 1997], and elastography [Sabra and Archer, 2009;Sabra et al, 2007]. For instance, ambient noise correlation processing has successfully been used to continuously monitor with unprecedented temporal resolution seismically active systems such as fault zones [Brenguier et al, 2008] and volcanic areas [Brenguier et al, 2014]. In the context of ocean acoustics [Roux et al, 2004;Godin et al, 2010;Fried et al, 2013;Brown et al, 2014], previous studies have demonstrated that the noise correlation method requires excessively long integration (i.e., averaging) times to reliably estimate the same discrete slanted acoustic paths used to infer temperature variations by previous acoustic thermometry studies conducted with active sources [The ATOC Consortium, 1998;Munk et al, 1995].…”