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One of aims of crustal structural expedition is to obtain P-wave velocity structures underneath the ocean bottom. Seismic data used here are deep penetrating refraction and wide-angle reflection waves generated by a large airgun array system.Ocean Bottom Seismographs (OBS) are settled on the sea bottom and positioned by using a real time super short base line (SSBL) acoustic positioning system with accuracy of 1-3% of water depth. Since we have required a high resolution seismic image, a super-densely deployed OBS array with spacing of a few to 10 km is preferred. These seismic methods using OBS can be used for understanding of deeper structure.

Survey Specification

SOURCE : Airgun (Bolt Technology Inc.)
Shot Interval : 100-200m
Total Volume : 12000cu.in.[200L] (1999-) / 4000cu.in.[66L](-1998)
Pressure : 2000psi

Ocean Bottom Seismograph (OBS) :
Maximum Depth : 6000m
Sensor : Three-component Geophone & Hydrophone
[One vertical and two horizontal components, Natural frequency:4.5Hz, Sensitivity:0.69V/inch/s(OPEN)]
Recording System : Sampling continuously (Timer control is possible for start time.)
Recording Media : DAT(digital audiotape) or Hard Disk
Sampling Rate : 100Hz
Power : Rechargeable lithium-ion or alkali battery
Accoustic Communication & Release System: Transponder,Transducer, Forced electrochemical erosion
Attached Parts : Weight, Flush light, Radio beacon
Pressure Resistant Container : 17 inch glass sphere

OBS Cruise List
Year Cruise ID Survey Area The Number of OBSs Period Deploy
ment 		Shooting Retrival Method
2012 KR12-20 Off Sanriku, Japan Trench 30 Dec.10.-Jan.08. * * * MCS
OBS
NT12-29 Off Kii Peninshula - Tokai, Nankai Trough 147 Nov.09.-Nov.26.     * OBS
KR12-12 Off Kii Peninshula - Tokai, Nankai Trough 156 Jun.29.-Aug.06. * *   MCS
OBS
NT12-11 Off Shikoku - Kii Peninshula, Nankai Trough 15 May.03.-May.10.     * OBS
KR12-10 Eastern Margin of Japan Sea 46 Apr.02.-May.13. * * * MCS
OBS
KY12-01 Nankai Trough, Off Shikoku - Off Kii 168 Jan.04.-Jan.19.     * OBS
2011 KR11-09 Nankai Trough, Off Shikoku - Off Kii 168 Sep.13.-Oct.10. * *   MCS
OBS
KR11-08 Eastern Margin of Japan Sea 55 Aug.03.-Aug.27. * * * MCS
OBS
KY11-E02 Izu-Bonin Arc 43 Mar.28.-Apr.05.     * OBS
KR11-05 Izu-Bonin Arc 43 Mar.03.-Mar.14. * *   MCS
OBS
NT11-01 Nankai Trough, Kii Suido 174 Jan.04.-Jan.22.     * OBS
2010 NT10-21 Nankai Trough, Kii Suido 174 Dec.20.-Dec.29.     * OBS
KR10-13 Izu-Bonin Arc 90 Dec.07.-Dec.28. * * * MCS
OBS
KR10-11 Nankai Trough, Kii Suido 174 Oct.13.-Nov.10. * *   MCS
OBS
KR10-10 Easetern Margin of Japan Sea 58 Aug.03.-Sep.06. * * * MCS
OBS
KY10-10 NW Pacific 101 Jul.16.-Jul.30.     * OBS
KR10-09 NW Pacific / Off Boso 101 Jul.01.-Jul.28. * *   MCS
OBS
KR10-05 Ontong-Java 100 Feb.25.-Mar.26. * * * MCS
OBS
KY10-02 Nankai Trough, Off Shikoku 201 Jan.28.-Feb.17.     * OBS
2009 KR09-17 NW Pacific 75 Nov.17.-Dec.12. * * * MCS
OBS
KR09-14 Nankai Trough, Off Shikoku 201 Sep.30.-Oct.20. * *   OBS
KY09-06 Eastern Margin of
Japan Sea		 30 Aug.06-Aug.19. * * * OBS
KY09-03 NW Pacific 90 Jul.05.-Jul.21.     * OBS
KR09-06 NW Pacific 90 Jun.19-Jul.05. * *   MCS
OBS
KY09-E01 Nankai Trough, Hyuganada 160 Jan.14.-Jan.28.     * OBS
2008 KR08-16 Nankai Trough, Hyuganada 160 Dec.07.-Dec.26. * *   OBS
KY08-E03 Izu-Bonin Arc 61 Nov.06.-Nov.21. *   * OBS
KY08-08 Izu-Bonin Arc 85 Aug.14.-Aug.28.   * * OBS
KR08-09 Izu-Bonin Arc /
Off Kumano		 85 Jul.27.-Aug.12. * *   MCS
OBS
KY08-04 Izu-Bonin Arc 110 May.14.-Jun.09. * * * OBS
KY08-02 Izu-Bonin Arc 105 Feb.28.-Mar.28. * * * OBS
2007 KY07-15 Izu-Bonin Arc 110 Nov.26.-Dec.23. * * * OBS
KR07-13 Izu-Bonin Arc 102 Sep.30.-Oct.29. * * * OBS
KR07-E01 off Niigata, Japan sea 40 Aug.18.-Aug.28. * * * MCS
OBS
KR07-10 Nankai Trough 78 Jul.28.-Aug.16. * * * OBS
KY07-07 Izu-Bonin Arc 110 May.15.-Jun.13. * * * OBS
KR07-03 Izu-Bonin Arc 100 Mar.04.-Mar.30. * * * MCS
OBS
2006 KY06-13 Off Kii Peninsula, Nankai Trough 90 Nov.07.-Dec.02. * * * OBS
KY06-09 Izu-Bonin Arc 95 Aug.03.-Sep.02. * * * OBS
KR06-05 Izu-Bonin Arc 100 May.15.-Jun.06. * * * MCS
OBS
KR06-01 Izu-Bonin Arc 100 Jan.05.-Jan.27. * * * OBS
2005 KY05-11 Izu-Bonin Arc 110 Oct.05.-Nov.03. * * * OBS
KY05-07 Izu-Bonin Arc 104 Jul.08.-Aug.01. * * * OBS
KY05-02 Izu-Bonin Arc 109 Feb.12.-Mar.11. * * * OBS
2004 KY04-13 Off Kii Peninsula, Nankai Trough 110 Nov.10.-Nov.29. * * * OBS
KR04-10
Leg 1 		Off Miyagi, Japan Trench 72 Aug.06.-Aug.19. * *   OBS
KY04-08 Izu-Bonin Arc 103 Jul.08.-Jul.28. * * * OBS
KY04-01 Off Kii Peninsula, Nankai Trough 100 Jan.11.-Feb.12. * * * OBS
2003 KR03-09 Off Sanriku, Japan Trench 60 Aug.06.-Aug.28. * * * MCS
OBS
KY03-06
Leg 2 		Middle Mariana Area 46 Jun.28.-Jul.16. * * * OBS
KY03-01
Leg 1 		Middle Mariana Area 106 Jan.09.-Feb.01. * * * OBS
2002 KY02-09
Leg 2 		Off Kumano, Nankai Trough 5 Sep.08.-Sep.24. * * * MCS
OBS
KY02-09
Leg 1 		Off Tottori, Japan Sea 35 Aug.25.-Sep.07. * * * OBS
2001 KY01-06 Off Tokai, Nankai Trough 170 Jul.29.-Sep.06. * * * OBS
2000 KY00-08 Off Miyake-jima / Kozu-shima 77 Oct.26.-Nov.05. * * * OBS
KY00-05 Off Nemuro, Kuril Trench / Okhotsk Sea 45 Jul.16.-Aug.14. * * * OBS
KY00-02 Off Aomori, Japan Trench 46 May.29.-Jun.23. * * * OBS
1999 KY99-05 Off Miyagi, Japan Trench 39 Jul.20.-Aug.20. * * * OBS
KY99-03 Off Muroto, Nankai Trough 98 Jun.01.-Jun.30. * * * OBS
KR99-04 Off Muroto, Nankai Trough 38 May.02.-Jun.10. *     MCS
OBS
1998 KY98-13 Off Muroto, Nankai Trough 15 Oct.31.-Nov.07.     * OBS
KR98-10 Off Muroto, Nankai Trough 15 Oct.07.-Oct.23. * *   MCS
OBS
KR98-06 Off Shikoku - Kumano, Nankai Trough 14 Jun.06-Jul.08. * * * MCS
OBS
KR98-04 Off Miyagi, Japan Trench 15 Apr.16.-May.05. * * * MCS
OBS
1997 KR97-07 Off Miyako, Japan Trench 26 Sep.30.-Oct.16. * * * MCS
OBS
KR97-04 Off Muroto, Nankai Trough 25 Jun.25.-Jul.22. * * * MCS
OBS

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