Principal objective and sub-goals
The main objective of this study is to improve our understanding of the structure, the stress conditions and sources, and the dynamics and deformation characteristics of the continental margin near Bear Island. The processes involved in the formation of the margin and the opening of the Atlantic are addressed, as well as the natural hazard exposure of the region. This will be accomplished by a well coordinated field campaign and associated data analysis efforts. The investigations will include: Detailed recovery of the crustal and lithosphere structure; improved hypocenter determination to identify the active tectonic faults; mapping of the deformation of sedimentary wedge of the steep continental slopes; calculation of focal mechanisms to study the complex stress field; investigation of the lithosphere low-velocity structure by surface wave analysis; study the imprint of the passive margin on crust and lithosphere using receiver functions and S-wave anisotropy.
Summary
A concentrated active and passive seismological experiment is proposed along the continental margin of the Barents Sea near Bear Island and the mid-Atlantic along the Knipovich Ridge. We will study the Earth's structure and dynamics at this margin from its top sedimentary cover to its imprint in the upper mantle. The continental margin in this region includes an extremely thick sedimentary wedge and steep slopes, with at least one major paleo fracture-zone cutting through the wedge. Recent studies in this area indicate very low seismic velocities in the lithosphere, which may be explained by a subcrustal extension of Mohns Ridge. The stress field undergoes an extensional-compressional transition in the region of the margin. It is therefore of particular interest to understand the structural architecture, the stress and the dynamics of the whole region because of its natural hazard exposure, and the processes involved in the formation of the margin and opening of the Atlantic.
The collection of deep seismic sounding data, and detailed monitoring and analysis of the seismicity between margin and mid-Atlantic ridge system, using temporary broadband stations, are necessary for providing such information. Data from existing seismic stations in the European Arctic (ARC/ARA0, Bear Island/BJO, KBS, JMI/JMIC, and SPI/SPA0), will also be analysed.
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Research area (red rectangle) on
the background of main tectonic elements. Gray triangles show location of seismic arrays and stations important for the project. |
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Map showing the area of interest and the locations of the planned active and passive seismological experiments. |
The planned field experiments comprise installation and parallel operation of seismic instruments during 2007-2008. This includes installation of a small broadband array on Bear Island and 12 broadband Ocean Bottom Seismometers (OBSs) from the German instrument pool for amphibian seismology (DEPAS).
In addition, we plan to install two broadband STS-2 seismometers one at the Polish Polar Station Hornsund and one on Hopen Island. We also plan to perform active seismic refraction/reflection experiments along two profiles crossing the mid-Atlantic ridge systems, the margin and Bear Island. The profiles will be supplemented with about 50 short-period stations on Bear Island and about 15 short period OBSs to retrieve the 3D lithosphere structure.
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