Cruise inventory

FS Sonne SO215

Cruise summary report

Cruise Info. 
Ship name (ship code)FS Sonne (06BE)
Cruise identifierSO215
Cruise period2011-04-25 — 2011-06-11
StatusCompleted
Port of departureAuckland, New Zealand
Port of returnTownsville, Australia
PurposeResearch
ObjectivesSubduction zones are dynamically evolving features that mark the sites of plate consumption and the recycling of sediment and magmatic material. The Tonga-Kermadec island arc-deep-sea trench system is an ideal study site as it is the most linear, fastest converging and most seismically active of any of the world's subduction zones, and the system has evolved over a long period of geological time (>50 Myr). The rapidity and obliqueness of convergence makes the Louisville Ridge-Tonga-Kermadec Trench an ideal locality to determine the mechanical response of the crust and lithosphere to loading and, hence, the integrated strength of the lithosphere. This is important for assessing whether the coupling between the subducting and overriding plates is 'soft' or 'hard' as well as providing constraints on rheological structure. The Tonga-Kermadec Trench collision with the Louisville Ridge is also associated with a seismic gap, especially so in shallow seismicity. This makes this also an ideal locality to test the 'Kelleher- McCann' hypothesis that bathymetric features on the subducting plate may control aspects of arc seismicity. Our scientific objectives were addressed by an integrated marine geophysical experiment that comprises simultaneous seismic reflection (MCS) and wide-angle (WA) refraction, gravity, magnetic, bathymetry and sub-seabed high-resolution imaging of the Louisville Ridge-Tonga-Kermadec Trench collision system. The acquisition geometry included:

a) Profile A - a 400 km MCS/WA transect across the ridge-trench intersection, designed to determine the across-strike structure of the collision zone between the arc, across the forearc and trench, to the outer rise. Whilst also imaging the crust and uppermost mantle structure in the aseismic zone and high-curvature weak zone in the seaward wall of the trench, this profile also imaged deformation solely related to collision to allow distinction from that induced by seamount interaction with the overriding plate.
b) Profile B - a 425 km MCS/WA transect across the Louisville Ridge and moat as they ride the trench outer rise, designed to determine the mode of isostatic compensation beneath the ridge at the northernmost part of the chain, and the effect of collision on the mechanical strength and flexural response of the subduction system.
c) Profile C - a 725 km MCS/WA transect along the Louisville Ridge, traversing IODP drill sites. This transect extends across the Tonga-Kermadec Trench, and was designed to determine the structure of the Louisville Ridge (the pre-subduction crust), any along-ridge variation in crustal structure or underplating, how seamounts interact with the overriding plate upon their subduction, and how along-ridge variation in topography, crust and uppermost mantle structure relate to observed post-collision uplift.
d) Profile D - a 350 km MCS transect designed to investigate pre-subduction crustal structure "background".
e) Profile G - a 240 km MCS/WA transect designed to investigate the crustal structure of the forearc and deformation in the overriding plate.

Along each WA profile ocean-bottom seismographs (OBSs) were deployed at ~10-15 km intervals, to record airgun shots from an array configured for contemporaneous MCS / WA acquisition. Gravity, magnetic and swath bathymetry data were acquired along all profiles.
Chief scientistChristine Peirce (University of Durham, Department of Earth Sciences)
Cruise reportFS Sonne SO215 cruise report sonne215.pdf — access key 'C' (12.74 MB) 
Ocean/sea areas 
GeneralTasman Sea
SpecificLouisvile Ridge and its intersection with the Tonga-Kermadec Trench
Track chartsFS Sonne SO215 cruise track — sonne215trk.pdf (0.16 MB) 
Measurements 
Physical oceanography 
BathythermographQuantity: number of deployments = 24
Description: Expendible bathymetric thermograph
Other physical oceanographic measurementsQuantity: number of deployments = 1
Description: Sound velocity
Geology and geophysics 
Multi-beam echosoundingQuantity: activity duration in days = 37
Description: Atlas Parasound PS 70
Multi-beam echosoundingQuantity: activity duration in days = 47
Description: Swath bathymetry - Simrad EM120
Multichannel seismic reflectionQuantity: track kilometres = 240
Description: Profile G - 96 channel multichannel reflection seismic data - Sercel SEAL
Multichannel seismic reflectionQuantity: track kilometres = 350
Description: Profile D - 96 channel multichannel reflection seismic data - Sercel SEAL
Multichannel seismic reflectionQuantity: track kilometres = 425
Description: Profile B - 96 channel multichannel reflection seismic data - Sercel SEAL
Multichannel seismic reflectionQuantity: track kilometres = 400
Description: Profile A - 96 channel multichannel reflection seismic data - Sercel SEAL
Multichannel seismic reflectionQuantity: track kilometres = 725
Description: Profile C - 96 channel multichannel reflection seismic data - Sercel SEAL
Seismic refractionQuantity: track kilometres = 240
Description: Profile G - wide-angle refraction seismic data - 4 component OBS
Seismic refractionQuantity: track kilometres = 725
Description: Profile C - wide-angle refraction seismic data - 4 component OBS
Seismic refractionQuantity: track kilometres = 400
Description: Profile A - wide-angle refraction seismic data - 4 component OBS
Seismic refractionQuantity: number of deployments = 126
Description: Ocean-bottom seismograph (OBS) deployments
Seismic refractionQuantity: track kilometres = 425
Description: Profile B - wide-angle refraction seismic data - 4 component OBS
Gravity measurementsQuantity: activity duration in days = 47
Description: Gravity - LaCoste-Romberg - Air-Sea meter, base tied pre- and post-cruise
Magnetic measurementsQuantity: number of profiles = 5
Description: Magnetics - SeaSpy
Magnetic measurementsQuantity: number of surveys = 3
Description: Magnetics - SeaSpy
Data held at BODC 
Series/Profiles 
22  Bathythermograph (MBT/XBT)
Sound velocity and travel time in the water column
Vertical spatial coordinates
Temperature of the water column
Reference numbers
Sound velocity and travel time in the water column
Vertical spatial coordinates
Temperature of the water column
Reference numbers

BODC idDate/TimeLocationDoc.
17188372011-04-28 13:05 27° 48' 13" S  175° 56' 57" W  View metadata report for BODC series reference number 1718837
17188492011-05-01 13:15 27° 26' 30" S  177° 5' 34" W  View metadata report for BODC series reference number 1718849
17188502011-05-01 21:13 27° 4' 14" S  176° 2' 16" W  View metadata report for BODC series reference number 1718850
17188622011-05-02 05:25 26° 39' 1" S  174° 52' 19" W  View metadata report for BODC series reference number 1718862
17188742011-05-02 12:22 26° 15' 53" S  174° 49' 48" W  View metadata report for BODC series reference number 1718874
17188862011-05-02 16:47 26° 1' 4" S  174° 18' 57" W  View metadata report for BODC series reference number 1718886
17188982011-05-02 20:50 25° 51' 25" S  174° 54' 50" W  View metadata report for BODC series reference number 1718898
17189052011-05-03 19:58 25° 11' 30" S  177° 17' 31" W  View metadata report for BODC series reference number 1718905
17189172011-05-13 14:56 25° 31' 43" S  176° 6' 21" W  View metadata report for BODC series reference number 1718917
17189292011-05-15 22:59 28° 57' 28" S  173° 1' 37" W  View metadata report for BODC series reference number 1718929
17189302011-05-16 06:34 28° 9' 6" S  173° 42' 54" W  View metadata report for BODC series reference number 1718930
17189422011-05-16 11:12 27° 36' 46" S  174° 10' 5" W  View metadata report for BODC series reference number 1718942
17189542011-05-16 15:18 28° 9' 6" S  173° 42' 54" W  View metadata report for BODC series reference number 1718954
17189662011-05-16 20:54 26° 16' 50" S  174° 49' 44" W  View metadata report for BODC series reference number 1718966
17189782011-05-17 01:43 25° 33' 29" S  175° 10' 26" W  View metadata report for BODC series reference number 1718978
17189912011-05-17 07:00 24° 43' 53" S  175° 33' 43" W  View metadata report for BODC series reference number 1718991
17190052011-05-17 15:45 23° 35' 33" S  176° 5' 20" W  View metadata report for BODC series reference number 1719005
17190172011-05-27 14:10 25° 11' 4" S  175° 35' 34" W  View metadata report for BODC series reference number 1719017
17190292011-05-27 20:58 26° 14' 19" S  175° 50' 38" W  View metadata report for BODC series reference number 1719029
17190302011-06-02 00:32 25° 53' 30" S  177° 4' 0" W  View metadata report for BODC series reference number 1719030
17190422011-06-02 00:57 25° 53' 30" S  177° 4' 59" W  View metadata report for BODC series reference number 1719042
17190542011-06-02 01:24 25° 53' 30" S  177° 10' 59" W  View metadata report for BODC series reference number 1719054