A global Earth Magnetic Anomaly Grid (EMAG2) was compiled from satellite, ship and airborne magnetic measurements. (Maus et al., 2009) Over the continents and the Arctic we made use of exisiting magnetic anomaly grids, whereas original ship and airborne trackline data were processed over the rest of the oceans, wherever available. CHAMP satellite magnetic measurements provided the magnetic field at wavelengths above 330 km. The EMAG2 grid is available at http://geomag.org and http://ngdc.noaa.gov. Directional gridding Due to the sparsity of magnetic field measurements in the southern oceans, it is necessary to interpolate the magnetic field between tracklines. Our interpolation algorithm takes the direction of the magnetic lineations into account. Tje lineations are parallel to the isochrons, which are perpendicular to the gradient of the age of teh oceanic crust. We use the age grid of Müller et al. (2008). The magnetic field ad a given grid point is computet by Least Squares Collocation from the surrounding measurements. If the point is on land, we use an isotropic correlation function with Rc = 14 km correlation length. Over the oceans we use Rc = 56 km parallel to the isochrons and Rc = 14 km in the spreading direction. Measurements seperated from the grid point by an age discontinuity or a topographic feature are excluded from the collation.

During the cruise with S.V. EXPLORA within the Ross Sea on the second marine-geophysical expedition of the Federal Institute for Geosciences and Natural Resources (BGR) to Antarctica, in total 6,745 km of magnetic, gravity and digital reflection seismic lines and additionally 1,400 km gravity lines were acquired in the period from January 10th to March 2nd 1980. On 43 stations sonobuoy refraction measurements have been carried out. The main results are: (1) In the eastern part of the Ross Sea Shelf two striking discontinuities have been identified in the reflection seismics representing gaps in the sediments at the turn-over of the Upper Miocene to the Pliocene (ca. 7 mio years B.P.) and between the Middle and Upper Miocene (ca. 11.5 mio. years B.P.) according to results of DSDP boreholes. (2) In the southern part of the Ross Sea Shelf the basement is uncovered at depths over 700m due to a thrust of the shelf ice recently. (3) A structural unit extends alongside the meridian of 180° separating the Ross Sea into two different geologic regions. This unit is characterised by two basement highs with seismic velocities exceeding 5 km/sec. (4) In relation with the GANOVEX expedition two profiles have been measured off northern Victoria Land which indicate two large faults with a faulting amount of 2 km. Another area is characterised by intrusive and volcanic bodies.

Within the frame of the comprehensive SPOC project (Subduction Processes off Chile) the SONNE cruises SO161 Leg 2 and 3 have been conducted between October 16th and November 29th, 2001, off central Chile between 28° and 44° S. In that period some 5,300 km were surveyed with multichannel seismic (MCS) reflection, magnetic, gravity, high-resolution bathymetric and echographic methods. In addition, approximately 3,900 km were surveyed with the same spectrum of methods but without MCS. The total number of 2D profiles was 48. Target was the variation of the subduction properties between the convergent oceanic Nazca and continental Southamerica plates and the different conditions that might influence the subduction process as there are: (1) age of the oceanic crust, (2) its structure and composition, (3) its sedimentary cover, (4) its thermal state, (5) the subduction angle and obliquity, and (6) the terrigenous sediment afflux from the continent. Furthermore, special focus was given to the subduction front, the subduction interface, the structure of the slope as well as to the forearc basin structure and history, and the general distribution of gas hydrate indicating bottom simulating reflectors (BSR's). The results are to be compared with previous studies of the Chilean active margin, e.g. CONDOR (SO 101 and 103) and CINCA (SO 104). The SPOC target area was subdivided into three sub-areas A,B and C. One area was chosen for a detailed survey by aid of a narrowly spaced grid and for a close link with a lot of partners. This area is characterized by a distinctly different margin type south of it is assumed. Moreover, the subducting portion of the aseismic Juan Fernandez Ridge is located in that area representing another important target of the survey. Advantageous conditions enabled the survey of an east-west profile south of Chiloé Island, providing a section through the submerged coastal Cordillera into the flooded longitudinal valley. Some results of Leg 2 and 3 are: In all areas A, B and C no subduction bulge (outer high) in the oceanic crust was visible perhaps due to the shortness of the profiles. The sedimentary cover of the oceanic crust is exceptionally thin, and the crustal thickness is generally quite "normal" with around 7 km derived from relatively weak Moho reflections. In area B a so far magnetically unmapped region was filled providing reliable ages of the oceanic crust, and suggesting that the Challenger Fracture Zone abruptly terminates west of the area of investigation. The survey in area C yielded valuable information on the trench morphology. The so far unique MCS profile south of Chiloé island shows a very wide trench and allows to extrapolate the general conditions encountered an area A southward to approximately 44° S. It can be stated that the situation is in sharp contrast to the basin structures detected by industry profiles further north in the Golfo de Corcovado.

The Sonne Cruise SO122 was carried out by the Federal Institute for Geosciences and Natural Resources (BGR, Hannover) from 3rd August to 9th September 1997, in cooperation with GEOMAR (Kiel), the National Institute of Oceanography (NIO, Karachi) and the Hydrocarbon Development Institute of Pakistan (HDIP). During the joint project with R/V SONNE the Makran accretionary wedge off Pakistan should have been investigated in detail with multi-channel reflection seismics, magnetics and gravimetry. Intense fishery offshore Pakistan forced a change of the area of investigation to the south with the following objectives: investigation of the crustal structure and occurrence of the bottom simulating reflector (BSR) in the Makran accretionary wedge; investigation of the structure of the Murray Ridge System in order to reconstruct the geodynamic evolution of the eastern Indian Plate margin; determination of the origin of the crust underlying the Indus Fan and reconnaissance of the sedimentary history of the Indus Fan in order to reveal the uplift and erosion history of the Himalayas.

On the F.S. POLARSTERN cruise ANT-IV/3 (6th December, 1985 - 13th March, 1986) multichannel seismic measurements were carried out in parallel with magnetic and gravimetric measurements on 33 lines with a total length of 6,263 km. 3,350 km of the multichannel seismic lines have been processed aboard. The geophysical studies were designed to investigate the structure and geological development of the Weddell Sea continental margin from meridians zero to 60°W, and to define suitable and safe drilling locations for Leg 113 of the Ocean Drilling Program. The main results of the geophysical studies are: (1) The discovery of an approximately N50°E trending failed drift basin, following the trend of a negative magnetic anomaly and a positive gravity anomaly. (2) The discovery of two extensive wedge-shaped and symmetric basement units around a failed drift basin between longitudes 40°W and 20°W. The seismic characteristics, i.e. seismic velocities of 4 km/s and an internally divergent pattern of reflectors suggest that both wedges are formed from extrusive/intrusive volcanic rocks. (3) The confirmation of a major plate tectonic boundary trending approximately N80°E to N60°E, i.e. the EXPLORA-ANDENES escarpment. (4) The confirmation of a glaciogenic progradational wedge beneath the shelf of the Weddell Sea Embayment, made up of several thousand metres of sediments. (5) The definition of 13 suitable and safe drilling locations for ODP-Leg 113.