Seismic heating signatures in the Japan Trench subduction plate-boundary fault zone: evidence from a preliminary rock magnetic ‘geothermometer’

Yang, Tao; Dekkers, Mark J.; Zhang, Bo

doi:10.1093/gji/ggw013

Cited by 17 publications

(32 citation statements)

References 60 publications

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“…The combination of above‐mentioned mineral magnetic properties and SEM/EDS observations provides compelling evidence for the presence of monoclinic pyrrhotite confined to within the three narrow fault zones. In contrast, the plate‐boundary fault zone, which is composed mostly of scaly clays, is dominated by magnetite (see Yang et al, , for details). This difference could be due to the extreme physical/chemical conditions in active plate‐boundary fault zones, compared to the overlying wedge sediment sections (Sutherland et al, ), although further work is required to confirm this explanation.…”

Section: Discussionmentioning

confidence: 99%

“…These include frictional devolatilization of carbonates and hydrous silicates (e.g., Han et al, ; Rowe et al, ), trace element partitioning (e.g., Tanikawa et al, ), and maturation of organic matter (e.g., Savage et al, ). However, each of these approaches can only be applied under specific conditions, and sometimes detect a certain temperature range only (see Yang et al, , for details). Thus, to achieve a complete picture of frictional heating, yet other approaches are desired, either independent of or working in concert with existing methods.…”

Section: Introductionmentioning

confidence: 99%

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Thermal Alteration of Pyrite to Pyrrhotite During Earthquakes: New Evidence of Seismic Slip in the Rock Record

2018

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Seismic slip zones convey important information on earthquake energy dissipation and rupture processes. However, geological records of earthquakes along exhumed faults remain scarce. They can be traced with a variety of methods that establish the frictional heating of seismic slip, although each has certain assets and disadvantages. Here we describe a mineral magnetic method to identify seismic slip along with its peak temperature through examination of magnetic mineral assemblages within a fault zone in deep‐sea sediments cored from the Japan Trench—one of the seismically most active regions around Japan—during the Integrated Ocean Drilling Program Expedition 343, the Japan Trench Fast Drilling Project. Fault zone sediments and adjacent host sediments were analyzed mineral magnetically, supplemented by scanning electron microscope observations with associated energy dispersive X‐ray spectroscopy analyses. The presence of the magnetic mineral pyrrhotite appears to be restricted to three fault zones occurring at ~697, ~720, and ~801 m below sea floor in the frontal prism sediments, while it is absent in the adjacent host sediments. Elevated temperatures and coseismic hot fluids as a consequence of frictional heating during earthquake rupture induced partial reaction of preexisting pyrite to pyrrhotite. The presence of pyrrhotite in combination with pyrite‐to‐pyrrhotite reaction kinetics constrains the peak temperature to between 640 and 800°C. The integrated mineral‐magnetic, microscopic, and kinetic approach adopted here is a useful tool to identify seismic slip along faults without frictional melt and establish the associated maximum temperature.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thermal Alteration of Pyrite to Pyrrhotite During Earthquakes: New Evidence of Seismic Slip in the Rock Record

2018

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“…This critical value can be higher if we consider a higher pore pressure caused by thermal or thermochemical pressurization, but, at the same time should be lower than 343°C which would correspond to a pore pressure equal to the lithostatic pressure (<15 MPa). In fact, as constrained from various temperature proxies (fission tracks, reaction kinetics, magnetic analysis, and trace elemental and isotopic analyses, as well as Raman spectra, vitrinite reflectance, and biomarkers of carbonaceous materials) [e.g., Mishima et al, 2006;Hirono et al, 2006Hirono et al, , 2015Sakaguchi et al, 2007;Ishikawa et al, 2008;Hamada et al, 2009;Otsuki et al, 2009;Kuo et al, 2011;Savage et al, 2014;Yang et al, 2016], much higher temperatures (>276°C) have been reported for the slip zones associated with the aforementioned earthquakes. Taking the 1999 Chi-Chi earthquake, for example, where the principal fault slip occurred at 300 m depth in the Chelungpu scientific drilling [Tanaka et al, 2006], magnetic analysis of the slip materials within the core samples indicated that the slip zones have experienced temperatures of at least 400°C Journal of Geophysical Research: Solid Earth 10.1002/2016JB013824 [Mishima et al, 2006], which is consistent with the temperatures obtained by using the compositions of major and trace elements (>350°C by Ishikawa et al [2008]), inorganic carbon content (550°C by Hirono et al [2006]), and vitrinite reflectance geothermometry (400-626°C by Maekawa et al [2014]), as well as infrared and Raman spectroscopies (~700°C by Hirono et al [2015]).…”

Section: 1002/2016jb013824mentioning

confidence: 99%

Vaporization of fault water during seismic slip

2017

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Laboratory and numerical studies, as well as field observations, indicate that phase transitions of pore water might be an important process in large earthquakes. We present a model of the thermo‐hydro‐chemo‐mechanical processes, including a two‐phase mixture model to incorporate the phase transitions of pore water, occurring during fast slip (i.e., a natural earthquake) in order to investigate the effects of vaporization on the coseismic slip. Using parameters from typical natural faults, our modeling shows that vaporization can indeed occur at the shallow depths of an earthquake, irrespective of the wide variability of the parameters involved (sliding velocity, friction coefficient, gouge permeability and porosity, and shear‐induced dilatancy). Due to the fast kinetics, water vaporization can cause a rapid slip weakening even when the hydrological conditions of the fault zone are not favorable for thermal pressurization, e.g., when permeability is high. At the same time, the latent heat associated with the phase transition causes the temperature rise in the slip zone to be buffered. Our parametric analyses reveal that the amount of frictional work is the principal factor controlling the onset and activity of vaporization and that it can easily be achieved in earthquakes. Our study shows that coseismic pore fluid vaporization might have played important roles at shallow depths of large earthquakes by enhancing slip weakening and buffering the temperature rise. The combined effects may provide an alternative explanation for the fact that low‐temperature anomalies were measured in the slip zones at shallow depths of large earthquakes.

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“…Anomalous rock magnetic properties, often magnetic enhancement, have been reported in earthquake slip zones, for example, from the Nojima Fault (Japan), which ruptured during the 1995 Kobe Mj 7.3 earthquake (e.g., Enomoto & Zheng, ; Ferré et al, ), the Chelungpu Fault (Taiwan) that hosted the 1999 Mw 7.6 Chi‐Chi earthquake (e.g., Hirono et al, ), and the Yingxiu‐Beichuan Fault (YBF; Sichuan, China) that accommodated the 2008 Wenchuan Mw 7.9 earthquake (e.g., Li et al, ; Pei et al, ). Rock magnetic measurements thus have been proposed as a means to locate fault slip (e.g., Chou, Song, Aubourg, Lee, et al, ; Chou, Song, Aubourg, Song, et al, ; Ferré et al, ; Han et al, ; Hirono et al, ; Yang et al, , and references therein) and to constrain the maximum temperature rise caused by the frictional heating (e.g., Chou, Song, Aubourg, Song, et al, ; Hirono et al, ; Mishima et al, ; Yang et al, , ). However, a full appreciation of the rock magnetic approach for earthquake slip diagnosis and concomitant temperature rise requires a thorough understanding of the mechanisms of such magnetic changes.…”

Section: Introductionmentioning

confidence: 99%

High‐Velocity Friction Experiments Indicate Magnetic Enhancement and Softening of Fault Gouges During Seismic Slip

Yang

Chen

et al. 2019

JGR Solid Earth

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High-velocity friction experiments were conducted on two natural fault gouges retrieved from the Yingxiu-Beichuan fault zone (Sichuan, China), which accommodated the 2008 Wenchuan Mw 7.9 earthquake. The experiments simulate large earthquake slip; the rotary shear apparatus enables to gather information as a function of shear displacement (and slip velocity) in a single experiment. The two starting fault gouges are essentially paramagnetic with one containing goethite. The experimentally sheared gouges both show a significant magnetic enhancement and softening with increasing slip distance. Rock magnetic measurements reveal that magnetite was formed during the experiment due to thermochemical reactions of iron adsorbed on clay minerals (smectite, chlorite). Scanning electron microscope observations showed that the new magnetite occurs as spherical and sintered irregular aggregates. This implies a high-temperature origin. The peak temperatures are estimated numerically to range from~260 to~440°C. Also, during the experiment on the goethite-bearing fault gouge, goethite was altered, reduced to magnetite due to the decomposition of trace organic matter present in the starting material. Magnetic susceptibility and magnetization of sheared samples are linearly increasing with the temperature rise induced by frictional heating; coercivities are decreasing. The grain size of the newly formed magnetite increases with heating temperature. This demonstrates that short-duration frictional heating generated by fast seismic slip induces thermal alteration: neoformation of ferrimagnetic minerals leads to magnetic enhancement and softening of slip zones. Thus, rock magnetic methods are a useful tool for diagnosing the earthquake slip and estimating the temperature rise of coseismic frictional heating.

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Seismic heating signatures in the Japan Trench subduction plate-boundary fault zone: evidence from a preliminary rock magnetic ‘geothermometer’

Cited by 17 publications

References 60 publications

Thermal Alteration of Pyrite to Pyrrhotite During Earthquakes: New Evidence of Seismic Slip in the Rock Record

Thermal Alteration of Pyrite to Pyrrhotite During Earthquakes: New Evidence of Seismic Slip in the Rock Record

Vaporization of fault water during seismic slip

High‐Velocity Friction Experiments Indicate Magnetic Enhancement and Softening of Fault Gouges During Seismic Slip

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