Elasticity and anelasticity of polycrystalline material containing dislocations; toward understanding of seismic images in the mantle

2017 Fiscal Year Final Research Report

• Project/Area Number: 15K13560
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Solid earth and planetary physics
• Research Institution: The University of Tokyo
• Principal Investigator: Takei Yasuko 東京大学, 地震研究所, 教授 (30323653)
• Research Collaborator: SASAKI Yuto 東京大学, 地震研究所, 大学院生
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 転位 / 非弾性 / 地震波減衰 / アナログ実験

Outline of Final Research Achievements

Rock anelasticity causes seismic dispersion and attenuation and hence plays an important role in the interpretation of seismological structures. Effects of dislocations on the rock anelasticity, however, have been poorly understood. We experimentally investigated the dislocation-induced anelasticity near room temperature by using borneol (organic polycrystal) as a rock analogue. We found that (1) deformation mechanism of borneol changes from diffusion to dislocation creep at the differential stress of about 1 MPa, (2) after the dislocation creep, Young's modulus was significantly reduced, (3) characteristic frequency of the dislocation-induced anelastic relaxation exists between 1 MHz and 100 Hz, and (4) the modulus recovered due to a dislocation recovery during the anelasticity measurement. (5) We further developed a new experimental system to measure anelasticity during the dislocation creep.

Free Research Field

固体地球科学