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REPORT OF HYDROGRAPHIC AND OCEANOGRAPHIC RESEARCHES JAPAN COAST GUARD TOKYO, JAPAN Older issues http://www1.kaiho.mlit.go.jp/kikaku/kenkyu/liste.html

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI 36 136 138 140 142 144 146 34 32 30 28 26 Shikoku Basin Ridge Myojin-sho Shichito- Iwo-jima Ogasawara Trough Ogasawara Ridge Izu-Ogasawara Trench Kaitoku Smt. Pacific Ocean Funka-Asane Kita-Fukutoku Tai 24 Fukutoku-okanoba Minami-Hiyoshi Smt. Nikko Smt. 22 Parece Vela Basin 136 138 140 142 144 146-11.0-6.0-3.0-2.5-2.0-0.0 3.0

23 35' 23 30' 23 45' 23 40' 23 55' 23 50' Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc depth(km) -2.5-2.0-1.5-1.0-0.5 0.0 141 35' 141 40' 141 45' 141 50' 141 55' 142 00' 142 05' 142 10' Kita-Hiyoshi Smt. Naka-Hiyoshi Smt. Minami-Hiyoshi Smt. 23 20' 23 25' -4.5-3.0-2.0-1.5-1.0-0.0 2.0 depth,km 141 50' 142 00' 141 45'E 141 50'E 141 55'E 142 00'E 142 05'E 23 40' 23 40'N 23 40'N 23 35'N 23 35'N 23 30' 23 30'N 23 30'N 23 25'N 23 25'N 23 20' 23 20'N 23 20'N 141 50' 142 00' 141 45'E 141 50'E 141 55'E 142 00'E 142 05'E km 0 5 10-4.5-3.0-2.0-1.5-1.0-0.0 2.0 depth(km) -5520 496 599 683 765 852 955 1089 1295 1716 91020 Sidescan

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI km 0 5 10 File khiyoss02_mosaic.grd - Sidescan Grid 141 40' 141 50' 141 35'E 141 40'E 141 45'E 141 50'E 23 55'N 23 50' 23 50'N 23 45'N 23 40' 141 40' 141 50' 141 35'E 141 40'E 141 45'E 141 50'E 23 40'N -4.5-3.0-2.0-1.5-1.0-0.0 2.0-8674 400 520 623 724 831 959 1120 1355 1799 74846 Sidescan

09:00 8/6 23:00 Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc 141 40' 142 00' 142 20' Kita-Hiyoshi Smt. airgun1 23 40' 17:00 16:00 Naka-Hiyoshi Smt. 23 20' 18:00 19:00 Line2 21:00 20:00 19:00 15:00 22:00 20:00 MH6 MH7 14:00 MH8 23:00 MH10 MH2 21:00 16:00 13:00 MH4 15:00 MH9 13:00 00:00 8/7 12:00 14:00 22:00 11:00 MH1 12:00 10:00 MH3 01:00 11:00 02:00 10:00 03:00 Minami-Hiyoshi Smt. Line4 MH5 00:00 8/8 Line3 09:00 04:00 08:00 06:00 05:00 07:00 18:00 Line1 17:00 141 40' km 0 10 20 30 142 00' 142 20' -4.5-3.0-2.0-1.5-1.0-0.0 2.0 depth, km

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI Line1 MH1 SSW NNE NW Line3 MH1 SE MH9 MH3 MH7 MH2 MH5 WSW Line2 MH6 MH6 MH4 MH1 ENE Two way travel time (s) Two way travel time (s) Two way travel time (s) 10 km 10 km 10 km Line4 W MH8 MH1 E 10 km Two way travel time (s)

Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc Line1 Line2 MH9 MH6 Line3 MH7 MH1 MH1 MH4 MH2 MH5 MH3 MH1 NW SE NW Line4 MH8 MH1 SSW NNE WSW ENE W E W SE E

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI

Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc SSW NNE 0 10 20 30 40 50 WSW 60 ENE 0 10 20 30 40 2.23 2.23 4 4.77 2.28 3.47 2.40 2.40 2.43 2.43 3.41 3.41 4.41 4.41 2.50 2.60 2.40 4.34 2.45 2.52 3.34 4.34 2.40 2.52 2.60 3.34 3.27 3.27 4.27 4.27 4.52 2.45 3.21 3.21 4.21 4.21 4.90 2.38 2.30 2.30 3.03 3.03 3.15 4.15 4.15 4.09 4.03 4.09 4.03 5.57 5.57 5.57 5.58 5.54 6.60 3.18 3.29 3.95 3.95 3.29 3.93 3.93 5.91 5.89 5.91 5.81 5.84 5.84 4.72 3.40 3.84 3.84 2.17 2.17 3.80 3.80 2.14 2.14 2.11 2.11 4.20 4.20 5.20 2.09 2.09 2.06 2.06 2.04 2.04 10 6.30 6.30 6.10 6.10 6.10 6.10 6.26 6.26 3.07 3.80 3.80 2.28 2.28 3.23 3.23 3.66 3.66 4.43 4.43 4.61 4.61 5.39 5.39 1.92 2.08 2.08 2.48 2.48 3.80 3.80 3.49 3.49 2.38 2.43 2.43 3.45 3.45 2.33 3.42 3.42 3.38 3.38 2.28 2.22 3.35 3.35 3.32 2.22 3.32 3.30 3.30 1.97 3.17 60 4.06 4.03 4.03 2.96 2.96 5.97 5.64 5.96 5.96 5.94 4.57 5.10 2.92 2.90 2.85 2.85 2.81 2.81 5.10 2.89 4.57 5.64 2.89 5.46 5.46 2.92 5.94 2.90 5.97 4.06 3.08 3.08 3.17 1.97 3.26 3.26 2.28 2.33 2.38 2.50 2.50 3.07 1.92 6.10 6.10 6.32 6.32 11 3.22 3.80 3.20 8 6.07 3.22 3.80 3.68 6.10 12 6.60 6.07 6.13 3.80 6.10 6.13 6.20 6.10 6.20 6.30 2.01 6.10 6.30 2.01 5.98 6.06 6.06 3.68 5.98 3.38 5.20 3.38 5.81 5.85 4.72 5.85 5.87 5.87 5.89 5.91 5.91 3.40 3.88 3.88 5.61 3.97 3.97 5.57 5.58 5.61 5.51 5.51 3.98 5.53 4.77 3.98 5.53 5.54 3.12 3.18 3.07 3.05 3.12 3.09 3.05 3.07 3.09 3.15 4.90 4.63 4.63 4.47 4.47 2.38 4.52 3.47 2.28 6 DEPTH (km) 2.50 2 DEPTH (km) 8 5 2 50 0 0 14 2.5 T-D/6 (s) 1.5 2.0 2.0 1.5 1.0 MH6 0.5 0.5 1.0 MH9 0 20 10 30 DISTANCE (km) 20 40 30 40 0 60 50 60 DEPTH (km) 10 8 6 4 4.77 2.28 2.28 3.47 4.47 2.40 2.40 2.43 2.43 3.41 3.41 4.41 4.41 2.50 2.50 2.45 2.45 2.60 2.60 2.52 2.52 3.21 3.21 4.21 4.21 3.34 3.34 4.34 4.34 2.40 2.40 3.27 3.27 4.27 4.27 4.52 3.47 4.52 4.90 0 2.30 3.03 3.03 3.09 4.09 4.09 4.15 4.15 5.57 5.57 5.58 5.61 5.58 5.91 5.91 6.60 5.89 5.87 5.89 3.29 4.72 5.84 5.84 4.72 5.81 5.81 3.84 3.84 3.40 2.17 2.17 2.14 2.14 2.11 4.20 5.20 2.11 2.09 2.09 2.06 2.06 2.04 2.04 6.10 6.10 6.10 6.10 6.30 6.07 6.30 6.26 6.26 20 3.80 3.22 3.07 3.80 3.80 2.28 2.28 3.23 3.23 3.66 3.66 4.43 4.43 4.61 4.61 5.39 5.39 1.92 2.08 2.08 3.80 3.80 2.48 3.49 3.49 2.38 2.50 2.50 3.07 1.92 2.48 3.22 3.80 40 30 2.43 2.43 3.45 3.45 3.42 3.42 3.38 3.38 2.28 2.22 3.35 3.35 3.32 2.22 3.32 3.30 3.30 3.26 50 40 60 3.17 50 60 4.03 2.96 2.96 5.97 5.97 5.96 5.96 2.92 5.64 5.94 4.57 5.10 2.90 2.85 2.85 2.81 2.81 5.10 2.89 2.89 4.57 5.64 2.92 2.90 5.46 5.46 5.94 4.06 3.08 4.03 4.06 3.08 3.17 1.97 1.97 3.26 2.28 2.33 2.33 2.38 6.10 6.10 6.32 6.32 11 6.07 6.13 12 6.60 6.13 6.20 3.20 6.10 6.20 3.80 6.10 6.06 2.01 3.68 3.68 6.10 5.98 6.10 6.30 2.01 5.20 5.98 6.06 6.30 3.38 3.80 3.80 4.20 3.38 5.85 5.85 5.87 10 3.40 3.88 3.88 5.51 5.57 5.91 5.91 3.29 3.93 5.61 3.18 5.51 5.53 5.54 5.54 3.93 5.57 3.95 3.97 3.97 5.53 3.98 3.95 4.77 3.98 3.12 3.18 3.07 3.12 3.05 4.03 3.05 4.03 3.07 3.09 3.15 30 DISTANCE (km) 2.30 2.38 4.63 4.63 4.47 4.90 2.38 3.15 2 DEPTH (km) 2 20 10 0 2.23 2.23 50 0 10 5 0 8 T-D/6 (s) 2.5 3.0 3.0 3.5 3.5 14 14 14 2.5 T-D/6 (s) 1.5 2.0 2.0 1.5 1.0 MH1 MH4 0.5 0.5 1.0 T-D/6 (s) 2.5 3.0 3.0 3.5 3.5 0 10 0 20 10 30 DISTANCE (km) 20 40 30 40 0 60 50 20 30 DISTANCE (km) 40 50 60 0 10 20 30 40 50 60 10 60 2.23 0 2.23 50 DEPTH (km) 10 8 6 4 2.28 2.28 3.47 2.40 2.40 2.43 2.43 3.41 2.60 3.34 2.52 2.60 3.34 3.27 2.52 3.27 4.27 3.47 4.41 4.63 2.45 2.40 4.27 4.34 4.47 2.40 3.41 4.52 4.41 4.77 2.50 4.52 2.45 3.21 3.21 4.21 4.21 4.90 2.38 2.30 2.30 3.03 3.03 3.15 4.15 4.15 3.09 4.09 4.09 4.03 5.61 5.58 5.57 5.58 5.51 5.57 5.57 3.93 3.29 3.29 3.88 3.88 3.93 5.91 5.91 5.91 5.89 5.89 5.87 5.87 5.91 5.85 5.84 5.84 5.81 5.85 4.72 5.81 3.40 3.40 3.84 3.84 3.80 3.80 4.20 2.17 2.17 2.14 2.14 2.11 2.11 4.20 2.09 2.09 2.06 2.06 3.38 4.72 5.57 5.61 5.20 3.18 4.77 5.51 3.95 3.95 5.53 5.54 3.97 3.97 5.54 3.12 3.98 5.53 3.07 3.18 3.98 3.05 3.12 4.03 3.05 3.07 3.09 3.15 4.63 4.47 4.90 4.34 2.38 0 2.50 5.98 6.06 3.38 2.04 2.04 6.10 6.10 6.10 6.30 6.30 6.20 6.30 6.20 6.13 6.13 6.07 6.07 6.26 6.26 14 2.28 3.22 3.07 3.80 1.92 1.92 2.08 2.08 2.50 3.80 3.23 3.23 3.66 3.66 2.48 4.43 4.43 4.61 4.61 5.39 5.39 3.49 3.49 2.38 2.50 3.07 3.80 2.28 2.48 3.80 2.43 3.45 3.45 2.33 2.33 3.38 3.38 2.28 3.42 3.42 2.22 3.35 3.32 3.32 3.30 3.30 3.26 2.22 3.26 3.17 4.06 3.08 2.96 2.96 5.94 5.46 5.64 5.94 5.97 5.97 2.92 2.92 4.57 4.57 5.10 2.90 2.90 5.46 2.89 5.10 2.85 2.85 2.81 2.81 2.89 5.64 4.03 4.03 3.17 4.06 1.97 1.97 3.08 2.28 3.35 2.38 2.43 5.96 5.96 6.10 6.10 6.32 6.32 11 3.5 3.5 3.0 3.0 2.5 2.5 T-D/6 (s) 1.5 2.0 2.0 1.5 1.0 MH3 0 10 Fig. 8 20 30 DISTANCE (km) 40 50 MH1 0.5 0.5 1.0 T-D/6 (s) 3.22 3.80 14 3.80 3.20 6.10 6.30 12 3.80 6.10 6.60 6.60 3.68 6.10 6.10 2.01 6.10 2.01 3.68 5.98 6.06 5.20 2 5 8 2 DEPTH (km) 60 0 Ray diagrams (top) and comparison between 10 20 30 DISTANCE (km) 40 Fig. 9 Same as Fig. 8 but for Line 2. observed and calculated travel times for each OBS along Line 1 (bottom). The observed travel times are indicated by vertical bars and the calculated ones by lines. The reduction velocity is 6.0 km/s. 11 50 60

0 10 20 30 40 50 60 10 8 6 4 2 0 DEPTH (km) 3.43 3.43 3.36 3.36 3.28 3.28 3.21 3.21 3.20 3.20 3.18 3.18 3.15 3.15 3.12 3.12 3.09 3.09 3.06 3.06 3.03 3.03 4.90 4.90 4.90 4.90 4.90 4.67 4.67 4.56 4.56 5.37 5.37 5.19 5.19 5.13 5.13 5.10 5.10 5.08 5.08 5.05 5.05 5.03 5.03 5.21 5.21 0 10 20 30 40 50 60 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 10 8 6 4 2 0 DEPTH (km) 3.43 3.43 3.36 3.36 3.28 3.28 3.21 3.21 3.20 3.20 3.18 3.18 3.15 3.15 3.12 3.12 3.09 3.09 3.06 3.06 3.03 3.03 4.90 4.90 4.90 4.90 4.90 4.67 4.67 4.56 4.56 5.37 5.37 5.19 5.19 5.13 5.13 5.10 5.10 5.08 5.08 5.05 5.05 5.03 5.03 5.21 5.21 0 10 20 30 40 50 60 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) MH8 MH1 W E 0 10 20 30 40 50 60 70 14 12 10 8 6 4 2 0 DEPTH (km) 1.93 1.93 2.18 2.18 2.16 2.16 2.13 2.13 2.11 2.11 3.42 3.42 3.28 3.28 3.09 3.09 2.92 2.92 2.12 2.12 2.14 2.14 2.14 2.14 2.17 2.17 2.19 2.19 2.83 2.83 2.88 2.88 2.93 2.93 3.51 3.51 3.51 3.51 3.53 3.53 3.54 3.54 3.56 3.56 3.58 3.58 3.60 3.60 3.36 3.36 3.60 3.60 2.90 3.69 2.90 3.69 3.30 3.83 3.30 3.83 5.48 5.48 4.41 4.72 4.41 4.72 4.20 4.75 4.20 4.75 4.32 4.32 4.40 5.07 4.40 5.07 4.25 5.15 4.25 5.15 4.20 5.53 5.53 5.73 5.73 5.36 5.72 5.36 5.72 5.84 6.21 5.84 6.21 5.13 5.13 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 14 12 10 8 6 4 2 0 DEPTH (km) 1.93 1.93 2.18 2.18 2.16 2.16 2.13 2.13 2.11 2.11 3.42 3.42 3.28 3.28 3.09 3.09 2.92 2.92 2.12 2.12 2.14 2.14 2.14 2.14 2.17 2.17 2.19 2.19 2.83 2.83 2.88 2.88 2.93 2.93 3.51 3.51 3.51 3.51 3.53 3.53 3.54 3.54 3.56 3.56 3.58 3.58 3.60 3.60 3.36 3.36 3.60 3.60 2.90 3.69 2.90 3.69 3.30 3.83 3.30 3.83 5.48 5.48 4.41 4.72 4.41 4.72 4.20 4.75 4.20 4.75 4.32 4.32 4.40 5.07 4.40 5.07 4.25 5.15 4.25 5.15 4.20 5.53 5.53 5.73 5.73 5.36 5.72 5.36 5.72 5.84 6.21 5.84 6.21 5.13 5.13 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 14 12 10 8 6 4 2 0 DEPTH (km) 1.93 1.93 2.18 2.18 2.16 2.16 2.13 2.13 2.11 2.11 3.42 3.42 3.28 3.28 3.09 3.09 2.92 2.92 2.12 2.12 2.14 2.14 2.14 2.14 2.17 2.17 2.19 2.19 2.83 2.83 2.88 2.88 2.93 2.93 3.51 3.51 3.51 3.51 3.53 3.53 3.54 3.54 3.56 3.56 3.58 3.58 3.60 3.60 3.36 3.36 3.60 3.60 2.90 3.69 2.90 3.69 3.30 3.83 3.30 3.83 5.48 5.48 4.41 4.72 4.41 4.72 4.20 4.75 4.20 4.75 4.32 4.32 4.40 5.07 4.40 5.07 4.25 5.15 4.25 5.15 4.20 5.53 5.53 5.73 5.73 5.36 5.72 5.36 5.72 5.84 6.21 5.84 6.21 5.13 5.13 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 14 12 10 8 6 4 2 0 DEPTH (km) 1.93 1.93 2.18 2.18 2.16 2.16 2.13 2.13 2.11 2.11 3.42 3.42 3.28 3.28 3.09 3.09 2.92 2.92 2.12 2.12 2.14 2.14 2.14 2.14 2.17 2.17 2.19 2.19 2.83 2.83 2.88 2.88 2.93 2.93 3.51 3.51 3.51 3.51 3.53 3.53 3.54 3.54 3.56 3.56 3.58 3.58 3.60 3.60 3.36 3.36 3.60 3.60 2.90 3.69 2.90 3.69 3.30 3.83 3.30 3.83 5.48 5.48 4.41 4.72 4.41 4.72 4.20 4.75 4.20 4.75 4.32 4.32 4.40 5.07 4.40 5.07 4.25 5.15 4.25 5.15 4.20 5.53 5.53 5.73 5.73 5.36 5.72 5.36 5.72 5.84 6.21 5.84 6.21 5.13 5.13 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) 0 10 20 30 40 50 60 70 DISTANCE (km) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 T-D/6 (s) MH7 MH2 MH1 MH5 SE NW SE NW Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI

Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc Line1 Line2 MH9 MH6 Line3 MH7 MH1 T-D/6 (s) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 0 10 20 30 40 50 60 T-D/6 (s) T-D/6 (s) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 T-D/6 (s) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 T-D/6 (s) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 T-D/6 (s) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 T-D/6 (s) 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 T-D/6 (s) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 MH1 MH3 0 10 20 30 40 50 60 0 10 20 30 40 50 60 DISTANCE (km) MH4 MH1 DISTANCE (km) SSW NNE WSW ENE 0 10 20 30 40 50 60 NW MH2 MH5 DISTANCE (km) 0 10 20 30 40 50 60 DISTANCE (km) SE 0 10 20 30 40 50 60 DISTANCE (km) T-D/6 (s) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Line4 W MH8 E NW 0 10 20 30 40 50 60 W MH1 DISTANCE (km) SE E

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI 0 SSW 1 2 3 4 D e p t h (km) 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 MH9 2.4 5.6 1.6 2 2.8 3.2 5.2 4.8 3.6 4 4.4 5.2 5?? 6 6 5.6 5.2 5.6 6 MH3 Line1 5 6? 7 8 9 10 0 10 20 30 40 50 60 2.4 3.6 4.8 2.8 5.2 3.2 1.6 4 4.4 5.6 5.2 5.6 2.4 1.6 3.6 2 3.2 4.4 4 4.8 2.8 4.8 5.2 5.2 5.6 6 NNE MH1 0 WSW MH4 1 Line2 ENE 2 2 MH6 3 4 5 6?? 7 8 9 10 0 10 20 30 40 50 60 D i s t a n c e (km) D e p t h (km) MH1 NW D e p t h (km) D e p t h (km) 0 1 2 3 4 7 8 9 1.6 2 3.2 3.6 2.4 4 5.2 6 2.8 4.4 5.2 4.8 5.6 MH7 MH2 1.6 2 2.4 2.8 3.2 3.6 4 4.4 4.8 1.6 2 3.2 2.4 2.8 3.6 4 5.2 5.2 6 4.4 4.8 5.6 5.6 MH5 Line3 10 0 10 20 30 40 50 60 70 W MH1 0 E 1 MH8 Line4 1.6 2 2 3 4? 5 0 10 20 30 40 50 60 D i s t a n c e (km) MH1 2 3 4 5 6 7 8 P wavespeed (km/s)? SE

Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc 2001 Aug.5 horizontal component 2001 Sep.7 MH1 MH5 MH1 MH5 horizontal component MH2 MH6 MH6 MH3 MH7 MH3 MH7 MH4 MH9 MH4 MH9

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI 2001 Aug.5 MH8 horizontal component 5-30HzBPF 2001 Sep.7 MH8 5-30HzBPF 2001 Sep.8 MH1 horizontal component 23-24h

Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc N 100 MH1 100 MH5 50 50 N 0 100 50 0 0 1 2 3 4 5 6 7 8 9 10 100 MH2 50 0 1 2 3 4 5 6 7 8 9 10 MH6 N 0 100 50 0 0 1 2 3 4 5 6 7 8 9 10 100 ~126 MH3 50 0 1 2 3 4 5 6 7 8 9 10 MH7 N 0 100 50 0 0 1 2 3 4 5 6 7 8 9 10 100 MH4 50 0 1 2 3 4 5 6 7 8 9 10 MH9 0 0 1 2 3 4 5 6 7 8 9 10 S-P time (sec) 0 0 1 2 3 4 5 6 7 8 9 10 S-P time (sec)

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI MH1V MH4V MH3V MH3H MH6V MH5V MH2V MH9V MH7V 1sec 138 140 142 36 141 20' 141 40' Kita-Fukutoku Tai 142 00' 34 24 20' Fukutoku-okanoba 32 30 28 24 00' 26 Fukutoku-okanoba Minami-Hiyoshi Smt. Nikko Smt. 24 Kita-Hiyoshi Smt. 22 23 40' Minami-Hiyoshi Smt. 23 20' 23 00' Nikko Smt. 141 20' 141 40' 142 00' 142 20'

1.6 2 2.4 4 3.6 2.4 12:00 13:00 14:00 7/5 99fuku07 11:00 15:00 11:00 16:00 12:00 10:00 10:00 7/4 13:00 21:00 14:00 99fuku04 03:00 99fuku05 02:00 7/5 15:00 04:00 20:00 05:00 06:00 17:00 99fuku06 09:00 19:00 08:00 7/5 18:00 2 2.4 2.8 3.2 2.4 4 3.2 4 airgun1 08:30 8/6 09:00 16:30 09:30 16:00 17:00 15:30 10:00 15:00 04:30 05:00 04:00 05:30 14:30 17:30 03:30 10:30 03:00 14:00 06:00 02:30 11:00 13:30 02:00 18:00 01:30 13:00 01:00 11:30 12:30 06:30 22:30 13:00 2 00:30 22:00 18:30 13:30 21:00 20:30 19:00 00:30 00:00 8/8 23:30 23:00 21:30 20:00 19:30 12:00 00:00 8/7 12:00 12:30 23:30 11:30 14:00 23:00 07:00 11:00 22:30 14:30 22:00 10:30 2 21:30 4 10:00 21:00 07:30 15:00 20:30 09:30 20:00 09:00 15:30 19:30 4 08:00 08:30 16:00 19:00 18:30 16:30 18:00 17:30 17:00 5.6 6 3.6 2 2 4 4 4.4 5.6 Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc 25 00' 24 30' 24 00' 23 30' 23 00' 141 00' 141 00' km Line4 0 10 20 30 141 30' Iwo-jima 141 30' Kita-Fukutoku Tai Line3 Line1 Line2 Line2 Line4 GMT 2002 Dec 5 16:51:29 /export/home6/hiyoshi/topo/nmariana_wgs84.grd -Jm1:1300000 142 00' Fukutoku-okanoba Minami-Iwo-jima Line1 Line3 142 00' Mt. Fuji 142 30' 1.6 2.4 2.8 Nikko Smt. Minami-Hiyoshi Smt. 3.2 3.6 1.6 4.4 4.8 2.4 2.8 5.2 142 30' -4.5-3.0-2.0-1.5-1.0-0.0 4.0 depth(km) 1999 Fukutoku-okanoba submarine volcano Line1 W E 1.6 1.6 2 3.2 3.2 3.6 MH9 5.6 4.4 5.2? 5 6? 4.8 5.2 5.6 D e p t h (km) 6 6 5.6 10 0 1 2 3 4 5 6 7 8 9 SSW Line1 NNE 0 10 20 30 40 50 60 WSW MH4 ENE 1.6 2 2.4 2.8 1.6 2 3.2 2.4 2.8 2.4 1.6 3.2 3.6 2.8 3.6 3.6 4 4.4 4 4.4 4.8 5.2 4.8 5.2 5.2 5.6 5.6 6 MH6 2.4 4 2.8 4.4 3.2 4.8 3.6 5.2 4.8 5.6 5.2 4.8 5.6 5.2 D e p t h (km) 6 5.2 10 0 0 1 2 3 4 5 6 7 8 9 FK2 Line2 0 10 20 30 40 50 60 D i s t a n c e (km) FK3 3.2 2.8 3.6 3.6 1 2.4 3.2 2.8 2 4 3 4 4 3.6 5 0 MH1 MH1 NW MH7 Line3 SE 1 MH2 MH3 MH5 D e p t h (km) MH1 FK4 FK5? 10 2 3 4 7 8 9 0 10 20 30 40 50 60 70 W 0 MH1 E Line4 2.4 1.6 2 2.8 3.2 1.6 MH8 4.4 4.8 5.2 D e p t h (km) D e p t h (km) 0 5 10 15 20 25 30 35 D i s t a n c e (km) Line2 W E FK7 FK9 1.6 0 2 1.6 2.4 2 2.8 3.2 3.6 3.2 2.8 3.6 3.2 2.8 4 1 3.6 2 4.4 3.6 3 D e p t h (km) 4.8 4 5 0 5 10 15 20 25 30 35 D i s t a n c e (km)?? Line3 SSW NNE 1 0 1 2 3 4 5 FK6 FK3 FK1 4 2 3 4.4 4.8 4 1 2 3 4 0 5 D e p t h (km) 5 FK1 FK4? 0 10 20 30 40 50 60 D i s t a n c e (km) FK9 D e p t h (km)???? 2001 Minami-Hiyoshi Seamount Line4 NNW SSE???? 0 5 10 15 20 25 30 D i s t a n c e (km)? 0 5 10 15 20 25 D i s t a n c e (km) 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 P wavespeed (km/s)

Azusa NISHIZAWA, Tomozo ONO, Noboru SASAHARA, Hiroshi HASHIGUCHI and Yasuo OTANI Phys. Earth Planet. Int. 47 30 36

Ocean Bottom Seismographic Observation at Minami-Hiyoshi Seamount at the Northern End of the Mariana Arc 37 38 Geophys. Res. Lett 29 39 20 39 5 Geophys. Res. Lett 29 35 79 Can. J. Explor. Geophys 24

Ken-ei ONODERA, Tsuyoshi KATO, Noritsune SEO

Crustal Structure in the Vicinities of Fukutoku-okanoba Submarine Volcano Estimated from Gravity and Magnetic Anomalies

Ken-ei ONODERA, Tsuyoshi KATO, Noritsune SEO

Crustal Structure in the Vicinities of Fukutoku-okanoba Submarine Volcano Estimated from Gravity and Magnetic Anomalies

Ken-ei ONODERA, Tsuyoshi KATO, Noritsune SEO

Crustal Structure in the Vicinities of Fukutoku-okanoba Submarine Volcano Estimated from Gravity and Magnetic Anomalies

Ken-ei ONODERA, Tsuyoshi KATO, Noritsune SEO

Crustal Structure in the Vicinities of Fukutoku-okanoba Submarine Volcano Estimated from Gravity and Magnetic Anomalies 38 39 35 33 23 Jour. Geophy. Res. 93 Geol. Soc. Am. Bull 84