Publication Date:
2018-02-03
Description:
I have used Euler-vector clustering to assign 469 GEONET stations in southwest Japan to k clusters ( k =2, 3,..., 9) so that for any k the velocities of stations within each cluster are most consistent with rigid-block motion on a sphere. That is, I attempt to explain the raw (i. e., uncorrected for strain accumulation), 1996-2006 velocities of those 469 GPS stations by rigid motion of k clusters on the surface of a spherical Earth. Because block geometry is maintained as strain accumulates, Euler-vector clustering may better approximate the block geometry than the values of the associated Euler vectors. The microplate solution for each k is constructed by merging contiguous clusters that have closely similar Euler vectors. The best solution consists of three microplates arranged along the Nankaido Trough-Ryukyu Trench between the Amurian and Philippine Sea Plates. One of these microplates, the South Kyushu Microplate (an extension of the Ryukyu forearc into the southeast corner of Kyushu), had previously been identified from paleomagnetic rotations. Relative to ITRF2000 the three microplates rotate at different rates about neighboring poles located close to the northwest corner of Shikoku. The microplate model is identical to that proposed in the block model of Wallace et al. (2009) except in southernmost Kyushu. On Shikoku and Honshu, but not Kyushu, the microplate model is consistent with that proposed in the block models of Nishimura & Hashimoto (2006) and Loveless & Meade (2010) without the low-slip-rate boundaries proposed in the latter.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
Permalink