Mica kink-band geometry as an indicator of coseismic dynamic loading

Energy Partitioning, Dynamic Fragmentation, and Off‐Fault Damage in the Earthquake Source Volume

“…R. Song, Johnson, Song, et al, 2020;Sullivan & Peterman, 2017) and garnet (e.g., Austrheim et al, 2017;Hawemann et al, 2019;Jamtveit et al, 2019;Petley-Ragan et al, 2019;B. R. Song, Johnson, Song, et al, 2020;Trepmann & Stöckhert, 2002), intense kinking of micas (Anderson et al, 2021;Bestmann et al, 2011), mechanical twinning of jadeite (Trepmann & Stöckhert, 2001), unusual quartz microstructures (e.g., Bestmann et al, 2011Bestmann et al, , 2012Price et al, 2016;Trepmann & Stöckhert, 2003), and variations in fluid-inclusion abundance (W. J. in the deeper seismogenic zone have more recently been attributed to coseismic loading. Existing experimental, theoretical, and numerical work points to dynamic stresses being largely responsible for this damage, although elevated-strain-rate, quasistatic loading during post-seismic creep may also make a measurable contribution.…”

Elastic Contrast, Rupture Directivity, and Damage Asymmetry in an Anisotropic Bimaterial Strike‐Slip Fault at Middle Crustal Depths

“…Using fragment size distribution analysis with three-dimensional D-value greater than 2.5, the boundaries between fractured and pulverized zones are located at ∼63 m in the QF and ∼5 m in the schist unit from the lithologic contact, indicating highly asymmetric distribution of pulverized zones as well (Figure 2d; B. R. . The wider pulverized zone determined by fragmented garnet in the QF unit is comparable to the dynamic strain-rate region (∼60 m wide) determined by muscovite kink-band geometries (Anderson et al, 2021) and the coseismic damage zone (∼90 m wide) determined by spatial abundance of fluid inclusions in the QF rocks (W. J. . have summarized these relations and their implications for energy expenditure in the earthquake source.…”

High Stress Deformation and Short‐Term Thermal Pulse Preserved in Pyroxene Microstructures From Exhumed Lower Crustal Seismogenic Faults (Lofoten, Norway)

“…In both cases the stress amplification can be significant within and just below the frictional-viscous transition zone (e.g., >300-500 MPa, Ellis & Stöckhert, 2004;Trepmann & Stöckhert, 2001;Brückner & Trepmann, 2021), but earthquake rupture of the lower crust may require stresses on the order of GPa, especially within strong, anhydrous granulites in the absence of high pore fluid pressure. Such stress magnitudes prior to rupture have been implied by field characterization of pseudotachylyte-bearing faults (Campbell et al, 2020) and, perhaps more commonly, are also associated with deformation linked to coseismic loading once rupture propagation has initiated (e.g., Anderson et al, 2021). This microstructural record of progressive and transient stress variation throughout the earthquake cycle (Anderson et al, 2021;Bestmann et al, 2012;Brückner & Trepmann, 2021;Campbell & Menegon, 2019;Johnson et al, 2021;Mancktelow et al, 2022;Petley-Ragan et al, 2019) offers an under-explored opportunity to further constrain deformation mechanisms and conditions associated with both prerupture stress amplification and coseismic rupture within the lower crust.…”

“…Such stress magnitudes prior to rupture have been implied by field characterization of pseudotachylyte-bearing faults (Campbell et al, 2020) and, perhaps more commonly, are also associated with deformation linked to coseismic loading once rupture propagation has initiated (e.g., Anderson et al, 2021). This microstructural record of progressive and transient stress variation throughout the earthquake cycle (Anderson et al, 2021;Bestmann et al, 2012;Brückner & Trepmann, 2021;Campbell & Menegon, 2019;Johnson et al, 2021;Mancktelow et al, 2022;Petley-Ragan et al, 2019) offers an under-explored opportunity to further constrain deformation mechanisms and conditions associated with both prerupture stress amplification and coseismic rupture within the lower crust.…”

“…Intracrystalline deformation and recrystallization occurring over geologically rapid timescales (i.e., equivalent to the seismic cycle) have been previously recognized in fault zones and deformation experiments (Bestmann et al., 2012; Campbell & Menegon, 2019; Kidder et al., 2016; Kim et al., 2010; Küster & Stöckhert, 1999; Trepmann & Stöckhert, 2001), and recent work on both naturally and experimentally deformed mid‐to lower‐crustal rocks has linked similar microstructures to stress transients. In some cases, such microstructures can be clearly linked to localized stress amplifications associated with deep crustal earthquakes, whether stress increases were generated in situ within the lower crust (Anderson et al., 2021; Campbell et al., 2020; Hawemann et al., 2019) or were transferred from shallower crustal levels (Ellis & Stöckhert, 2004; Papa et al., 2020; Trepmann & Stöckhert, 2002, 2013). In both cases the stress amplification can be significant within and just below the frictional‐viscous transition zone (e.g., >300–500 MPa, Ellis & Stöckhert, 2004; Trepmann & Stöckhert, 2001; Brückner & Trepmann, 2021), but earthquake rupture of the lower crust may require stresses on the order of GPa, especially within strong, anhydrous granulites in the absence of high pore fluid pressure.…”