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Unusually large shear wave anisotropy for chlorite in subduction zone settings
Author(s) -
Mookherjee Mainak,
Mainprice David
Publication year - 2014
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2014gl059334
Subject(s) - chlorite , anisotropy , subduction , peridotite , shear (geology) , shear modulus , geology , mantle (geology) , materials science , mineralogy , geophysics , composite material , physics , seismology , petrology , optics , tectonics , quartz
Using first principle simulations we calculated the elasticity of chlorite. At a density ρ ~ 2.60 g cm −3 , the elastic constant tensor reveals significant elastic anisotropy: V P ~27%, V S 1 ~56%, and V S 2 ~43%. The shear anisotropy is exceptionally large for chlorite and enhances upon compression. Upon compression, the shear elastic constant component C 44 and C 55 decreases, whereas C 66 shear component stiffens. The softening in C 44 and C 55 is reflected in shear modulus, G , and the shear wave velocity, V S . Our results on elastic anisotropy at conditions relevant to the mantle wedge indicates that a 10–20 km layer of hydrated peridotite with serpentine and chlorite could account for the observed shear polarization anisotropy and associated large delay times of 1–2 s observed in some subduction zone settings. In addition, chlorite could also explain the low V P / V S ratios that have been observed in recent high‐resolution seismological studies.