International Geologiical Congress - Oslo 2008

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EIE-07 High-resolution geophysical imaging of geological structures and processes in environmental studies

 

Reflection seismic imaging of the end-glacial Pärvie fault system, northern Sweden

 

Christopher Juhlin, Uppsala University (Sweden)
Björn Lund, Uppsala University (Sweden)
Mahdieh Dehghannejad, Uppsala University (Sweden)
Alireza Malehmir, Uppsala University (Sweden)
 

 

The Pärvie fault system extends over more than 150 km and has a throw exceeding 10 meters. Based on studies of Quarternary deposits in its fault scarps it is inferred to be end-glacial in age and to have been generated by an 8 magnitude earthquake. A key question in understanding the nature of the Pärvie fault, and other similar faults in the northern Baltic Shield, is what the stress field was at the time of faulting. By assuming the tectonic stress to have been the same as today and knowing the geometry of the faults then the stress field at time of faulting can be estimated. In order to investigate the geometry of the Pärvie fault a c. 20 km long reflection seismic profile was acquired in 2007. Rocks exposed at the surface consist mainly of supracrustals with granitic rocks expected at deeper levels. First results indicate that the supracrustals extend to about 1 km depth with the base generating a strong wide-angle reflection. Three surface mapped faults are crossed and imaged; with the westernmost one, the main fault, dipping at 50-60 degrees to the east, the central one dipping at 70-80 degrees to the east and the easternmost one dipping 50-60 degrees to the west.

 

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