Long-Term Stability of Acoustic Benchmarks Deployed on Thick Sediment for GPS/Acoustic Seafloor Positioning - Accretionary Prisms and Convergent Margin Tectonics in the Northwest Pacific Basin - page 266

Fig. 2 PXP locations with their site names indicated. Nagoya and Tohoku sites correspond to N
and T in Fig. 1 . Solid circles are surveyed PXPs during this diving cruise, while open circles are
not. Dive courses are schematically shown by arrows with dive numbers
Three PXPs at the westernmost site deployed by the Nagoya University group
contributed to the detection of a co-seismic crustal movement (Tadokoro et al.
2006 ). Figure 3a-c show photographs of them on the seafloor. Figure 3d shows an
instrument before deployment. The reddish hard hut contains a glass-sphere pres-
sure vessel of 0.3 m in diameter, and the black unit on the top is an acoustic trans-
ducer. The bottom frame supporting the hard hut is buried in the sediment. Each
instrument stands almost vertical on the bottom, and there was nothing indicating
an effect of the earthquakes.
The ROV visited four of the five PXPs in the central array of the Tohoku
University group, which also detected the co-seismic movement (Kido et al. 2006 ).
As is shown in Fig. 4 , they sat stably on the floor. The yellow hard hut contains a
glass sphere of 0.4 m in diameter. The white bottom frame, 1 m in diameter, stably
holds the hard hut.