科研之友
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摘要
Broad-band body and mantle wave data are used to study the 2004 December 23, Tasman Sea earthquake. In common with other strike-slip earthquakes studied in the same fashion, the mantle wave data indicates that there are two pure-double couple constrained solutions, along with a range of mechanisms between them, that fit the data almost equally well. Aftershocks relocated for this study indicate that the rupture occurred on a fracture zone which bends sharply in the epicentral region. Horizontally polarised S body waves and P body waves are used to determine the rupture parameters. A model with two faults best fits the data. The northern fault plane, with strike 160 degrees, dip 86 degrees and rake 5 degrees, is compatible with the first motion solution found in this study and has a strike consistent with the fracture zone north of the bend. The southern fault plane, with strike 178 degrees, dip 54 degrees and rake 65 degrees, has a strike consistent with the portion of the fracture zone to the south of the bend and has a dip which can be explained by the style of deformation that the region is undergoing. The centroid moment tensor solution of the broad-band model is calculated and found to be consistent with the region of low misfit in mantle wave solution space. The broad-band solution has a moment of 1.53 x 10(21)N m (M(w) 8.1), again, consistent with the mantle wave data. Slip propagated bilaterally with an approximate rupture velocity of similar to 3 km s(-1) similar to 80 per cent of local shear wave speed. The rupture front is less well resolved to the south of the epicentre than to the north. The majority (similar to 75 per cent) of moment originated from slip on the northern fault. The broad-band data requires significant slip below the oceanic Moho with as much as 70 per cent of moment due to slip in the brittle uppermost mantle in the preferred model.
- 出版日期2011-9
