Late Quaternary to decadal velocity fields in Asia

Abstract

Fields of crustal velocity and strain rate within Asia, averaged over horizontal distances of ∼300 km, are calculated from estimates of Quaternary slip rates on faults and rates of change of lengths of baselines between GPS sites. The calculated fields fit strain rate components estimated from Quaternary slip rates within 95% confidence limits and fit the GPS data with an RMS residual of 2.5 mm yr-1. The strain rate field constrained only by Quaternary slip rates of faults differs from the combined solution at the level of 20 nstrain yr-1, and the differences are explicable by the limited accuracy of geological estimates of slip rate. Therefore the strain rate fields determined by geodetic measurements taken on the 10-year timescale are consistent with geological observations on the 104-year timescale. The combined solution for velocities shows plate- or block-like motion within deforming Asia only in Tarim, south China, and the Amurian region; elsewhere the kinematics of rigid blocks does not provide a useful description of the motion. In particular, velocities relative to Eurasia point at high angles to contours of their magnitudes, not parallel to them as they would if large regions moved as rigid blocks. The axes of principal horizontal compressional strain align with topographic gradients, in agreement with previous suggestions that Asia deforms as a continuum under the influence of gravity. Copyright 2005 by the American Geophysical Union.