PASSEQ 2006-2007 - Passive Seismic Experiment in TESZ: Recognition of the lithosphere-asthenosphere system in the transition between Proterozoic and Phanerozoic Europe

Richard England

Our understanding of the physical properties of the continental lithosphere and its response to deformation are largely based on studies of the crust, which is easily accessible to geological and geophysical study. The properties and role of the mantle lithosphere is less well understood. Much can be learnt from the study of post rift subsidence patterns of sedimentary basins or from relaxation of strains caused by faulting. However, recent developments in seismic tomography, receiver function and SKS analysis have made it possible to attempt to study the structure of the mantle lithosphere in detail. This knowledge will contribute to a better understanding of the mechanisms of continental evolution and deformation. For example, it will permit us to test the validity of models for basin formation and heat flow in different types of lithosphere and determine better the response of the lithosphere to unloading as a result of deglaciation or major faulting events.

The Caledonian (c. 400 Ma) suture zone between the East European Craton and the Palaeozoic mobile belts of western Europe is one of the most distinct on Earth, making it an ideal natural laboratory to investigate the physical properties of adjacent contrasting lithospheres. Recent extensive seismic wide-angle profiling  has shown that thick (40 - 45 km) crust beneath the craton is separated from thinner (c. 30 km) thick crust beneath western Europe by the near vertical and narrow (c. 60 km wide) Trans European Suture zone (TESZ). Shear wave tomography  has shown that this boundary is as distinct within the mantle lithosphere as it is in the crust. In contrast there is little evidence of the suture at the surface. A near flat peneplained topography is formed on a Mesozoic/Cenozoic transtensional sedimentary basin developed over the suture zone.

To study this boundary and the properties of the crust on either side of it colleagues from the University of Warsaw have invited geophysics groups from across Europe to deploy a passive seismic network across the TESZ. 10 SEIS-UK instruments from Leicester are being deployed in July 2006 along the main profile to record, teleseismic and surface waves from distant earthquakes. The instruments will be recovered in November 2007 and the data analysed thereafter.

This is the most recent of a series of major seismic experiments conducted in Europe but is the first that UK researchers have been able to fully participate in for some time because of the limited numbers of suitable instruments available in the UK. The establishment of SEIS-UK has made participation in this experiment possible.

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Last updated: 13th July 2006
R.W.England
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