Open AccessThree‐dimensional structure of P‐wave anisotropy in the presence of small‐scale convection in the mantle wedge
Author(s) -
Morishige M.,
Honda S.
Publication year - 2011
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2011gc003866
Subject(s) - geology , mantle convection , convection , mantle wedge , mantle (geology) , geophysics , anisotropy , wedge (geometry) , slab , rheology , subduction , mechanics , seismology , physics , tectonics , optics , thermodynamics
As a possible explanation of “hot fingers” in the mantle wedge below the Tohoku region, Japan, the existence of small‐scale convection has been proposed. In this study, we performed numerical calculations around the subduction zone in 3D with composite rheology (i.e., a combination of linear and non‐linear rheology) and found that small‐scale convection could arise when the rheology determined from laboratory experiments is considered. We also calculated 3D structure of expected P‐wave anisotropy for the case with and without small‐scale convection based on a theory of LPO development and an assumption that anisotropy is approximately represented as hexagonal symmetry, and found that the fast axis of the P‐wave propagation projected on the horizontal cross‐sections is nearly in the same direction as that of plate motion in many places. It implies that effects of large‐scale mantle flow associated with subducting slab is still dominant even in the presence of small‐scale convection in mantle wedge. However, in vertical cross‐sections, the projected fast axis of the P‐wave propagation could tilt vertically while that without small‐scale convection is almost horizontal. Therefore, future seismological studies that determine the fast direction of P‐wave propagation in 3D would give us critical information on the possible existence of small‐scale convection in the mantle wedge.