The thought of this special issue stemmed from a topical session held on bPseudotachylytes1 and Seismogenic FrictionQ convened at the national meeting of the Geological Society of America, in Denver in November 2003. Natural pseudotachylytes form by asteroid impact on rocky planets or by catastrophic rupture resulting from large magnitude earthquakes and landslides. This special issue concentrates on faultrelated pseudotachylytes formed by coseismic, highvelocity friction. We introduce new results on the mechanisms of formation and the significance of pseudotachylytes, obtained mainly from structural, petrographic, geochemical and magnetic investigations.
This journal published a special issue on bFrictional melting processes and products in geological materialsQ masterly edited by Jerry Magloughlin and John Spray in 1992. Thirteen years later, the focus of pseudotachylyte studies seems to have shifted towards better understanding the seismic rupture mechanisms at depth.
The abundant literature dedicated to fault pseudotachylytes in the last decade is a testimony to the increasing interest of the scientific community for a geological approach to seismological problems. A few amongst many of these innovative investigations include the generation of artificial pseudotachylyte (e.g., Lin and Shimamoto, 1998; Kenkmann, 2000), progress in dating methods Ar–Ar methods (e.g., Magloughlin et al., 1998), thermodynamic models (e.g., O’Hara, 2001), metamorphic studies suggesting that pseudotachylytes may also form in the eclogite facies (e.g., Austrheim and Boundy, 1994), magnetic results pertaining to the origin of their magnetic remanence (e.g., Enomoto and Zheng, 1998; Nakamura et al., 2002) and the role of fluids (e.g., Boullier et al., 2001). Some of the questions unanswered by the above literature are addressed in this special issue.
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