In situ observations of earthquake-driven fluid pulses within the Japan Trench plate boundary fault zone

Abstract

Transient fluid flow within faults is suspected to be an important component of the earthquake cycle and subduction zone evolution. However, an understanding of the mechanisms and time scales involved has been limited due to a paucity of direct measurements. Here we report on in situ observations that appear to capture the thermal signature of earthquakedriven fluid pulses within the damage zone of the Japan Trench plate boundary fault. The data are from a sub-seafloor temperature observatory installed through the fault following the March 2011 M w 9.0 Tohoku-oki earthquake as part of the Integrated Ocean Drilling Program's Japan Trench Fast Drilling Project (JFAST). High-resolution temperature time series data reveal spatially correlated transients in response to earthquakes that are indicative of advection by transient fluid flow. We interpret the observed phenomenon as reflecting pressure redistribution in a fault zone and a potential mechanism for earthquake triggering and episodic heat and chemical transport.

Geophysics From Terrestrial Time‐Variable Gravity Measurements

“…Repeating well-positioned absolute gravity measurements can further probe the physical parameters of the mantle surrounding a subduction megathrust fault (Mazzotti et al, 2007). Measuring the ratio between deformations and gravity rates of change could also provide information on inelastic deformation and fluid transfers during the seismic cycle (Fulton & Brodsky, 2016).…”

Coupled Evolution of Deformation, Pore Fluid Pressure, and Fluid Flow in Shallow Subduction Forearcs

“…At nearly all subduction zones, at least some proportion of relative plate motion is accommodated by earthquakes or transient slow slip events. Fluctuations of stress, fluid pressure, and fluid flow rate throughout seismic and aseismic episodic slip cycles are expected to occur (e.g., Wang & Hu, 2006) and have been documented at various subduction margins (e.g., Davis et al, 2015; Fulton & Brodsky, 2016; Hasegawa et al, 2012; Sun et al, 2017; Tsuji et al, 2013; Wang et al, 2019; Warren‐Smith et al, 2019). A more complete understanding of the deformation and fluid processes over a broad range of timescales would require the combination of modeling studies of both long‐term processes such as the current study and those focusing on shorter term processes such as fault rupture and dynamic friction change.…”

Tōhoku-oki Fault Zone Frictional Heat Measured During IODP Expeditions 343 and 343T

“…Note that due to bathymetric differences between the separate coring and observatory holes, fault locations identified in the core are expected to be a few meters deeper relative to the seafloor than in the observatory (Chester et al, 2013b). Fluid advection is not seen within the plate boundary fault but is observed within the temperature data at shallower depths in response to a December 7, 2012, M w 7.3 earthquake and other aftershocks (Fulton and Brodsky, 2016). The differences in hydrologic and thermal response to earthquakes and drilling disturbance at different depths is indicative of the dominance of conductive heat transfer within the plate boundary fault (Fulton et al, 2013;Fulton and Brodsky, 2016).…”