Mode of seismic moment release at the Pacific-Antarctic Ridge (abstract)

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This paper presents an analysis of transform fault (TF) events along the Eltanin fracture zone (FZ) and the Udintsev FZ, the Pacific-Antarctic Ridge. We redetermined fault plane solutions and seismic moments of 12 TF events by moment tensor inversion (FITCH et al. : J. Geophys. Res., 85,3817,1980) using Claerbout's Robust modelling (CLAERBOUT and MUIR : Geophysics, 38,826,1973). Corrections for physical dispersion and instrumental response were made by a simple method same as that of CHUNG and KANAMORI (Phys. Earth Planet. Inter., 23,134,1980). Conclusions are as follows : (1) Events for which fault plane solutions were well-constrained were all left-lateral strike-slip fault events, which is consistent with the concept of the transform fault. (2) Total amount of the seismic moments released at the Eltanin FZ, the Pacific-Antarctic Ridge, is 6-7×(10)^<26>dyn・cm, including all of the TF events of the surface wave magnitude Ms greater than 5.8. The estimate is 8-10% of an amount of 7.5×(10)^<26>dyn・cm predicted by a simple plate kinematics with parameters of a TF length of 1300km, a crustal thickness of 10km, a rigidity of 4×(10)^<11>dyn・cm, a spreading rate of 9cm/yr and the period of 16 years. This indicates that the main part of transform fault movements was released aseismically at the Eltanin FZ. The conclusion (2) seems to be a proof for the conclusion that the fast-spreading center like the Pacific-Antarctic Ridge is hot and plastic because hot mantle materials are being supplied by the fast-moving mantle-convection current.
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Mode of seismic moment release at the Pacific-Antarctic Ridge (abstract)

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