Active extension of the Shanxi rift, north China: Does it result from anticlockwise block rotations?

Abstract

The Shanxi rift is an intraplate extensional zone in the North China Block. Active extension has previously been considered to result from anticlockwise block rotation, with successive indentation of the Indian plate toward the Eurasian plate. However, GPS data show that the entire North China Block is moving coherently from WNW to ESE, indicating that no significant block rotations presently exist along the two sides of the rift. We use a viscoelastic model to predict that its active extension might be caused by intraplate deformation localization with lateral changes of the crustal rheological structures. A model result shows that for the ESE movement of the North China Block, the existing topographical loading and crustal weakness could have resulted in the obvious long-term extension of the Shanxi rift even without different block rotations. The surface extension rate approximated from lateral inhomogeneous crustal models is ∼0.5-1.4 mm yr-1, consistent with observed geological and seismological extension rates. © 2003 Blackwell Publishing Ltd.