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sediment in order to reduce the shock at the landing after a free-fall in the sea water.
(2) Judging from the penetration at the landing and at push-coring, the sediment is
stiff enough to support them stably. (3) They have large resistance against sinking
into the sediment owing to the size of the bottom part that is much larger than the
diameter of the push-corer. (4) Because P wave velocity in unconsolidated sediment
is much the same with that in sea water, top part of the sediment and a seafloor
instrument must move much the same way with the sea water in case of an
earthquake.
One of old benchmarks was recovered after a long stay on the ocean bottom for
about 6 years. Outside of the recovered instrument was healthy enough to encourage
longer-term observation: there was no corrosion on the instrument by the sea water
nor damages by marine lives. Diving survey have provided us many important sug-
gestions, which should be utilized in seafloor instrumentation in the future.
Aknowledgements The authors thank Captain Y. Iwasaki, crew of the R/V Natsushima,
Commander K. Chiba, and team of the ROV Hyper-Dolphin for efficient operations during the
diving surveys. This study was supported by the Deep-sea Research Program of JAMSTEC, and
was partly supported by the program of Dense Oceanfloor Network System for Earthquakes and
Tsunamis (DONET) of JAMSTEC and MEXT, Japan.
References
Chadwell CD, Spiess FN (2008) Plate motion at the ridge-transform boundary of the south Cleft
segment of the Juan de Fuca Ridge from GPS-Acoustic data. Geophys Res Lett 113:B04415.
doi:10.1029/2007JB004936
Fujita M, Ishikawa T, Mochizuki M, Sato M, Toyama S, Katayama M, Kawai K, Matsumoto Y,
Yabuki T, Asada A, Colombo OL (2006) GPS/Acoustic seafloor geodetic observation: method
of data analysis and its application. Earth Planet Space 58:265-275
Gagnon K, Chadwell CD, Norabuena E (2005) Measuring the onset of locking in the Peru-Chile
trench with GPS and acoustic measuring. Nature 434:205-208
Geographical Survey Institute (GSI) (2004) The earthquake SE off Kii peninsula on September 5.
In: the Summary of the 159 Meeting of the Coordinating Committee for Earthquake Prediction.
http://cais.gsi.go.jp/YOCHIREN/JIS/159/index159.html
Hashimoto C, Noda A, Sagiya T, Matsu'ura M (2009) Interplate seismogenic zones along the
Kuril - Japan trench inferred from GPS data inversion. Nat Geosci 2:141-144
Kido M, Fujimoto H, Miura S, Osada Y, Tsuka K, Tabei T (2006) Seafloor displacement at
Kumano-nada caused by the 2004 off Kii Peninsula earthquake, detected through repeated
GPS/Acoustic surveys. Earth Planet Space 58:911-915
Matsumoto Y, Fujita M, Ishikawa T, Mochizuki M, Yabuki T, Asada A (2006) Undersea co-seis-
mic crustal movements associated with the 2005 Off Miyagi Prefecture Earthquake detected
by GPS/acoustic seafloor geodetic observation. Earth Planet Space 58:1573-1576
Spiess FN (1985) Analysis of a possible seafloor strain measurement system. Mar Geod
9:385-398
Spiess FN, Chadwell CD, Hildebrand JA, Young LE, Purcell GH Jr, Dragert H (1998) Precise
GPS/Acoustic positioning of seafloor reference points for tectonic studies. Phys Earth Planet
Inter 108:101-112
Tadokoro K, Ando M, Ikuta R, Okuda T, Besana GM, Sugimoto S, Kuno M (2006) Observation
of coseismic seafloor crustal deformation due to M7 class offshore earthquakes. Geophys Res
Lett 33. doi:10.1029/2006GL026742
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