Crustal deformation on the Chinese mainland during 1998—2004 based on GPS data

This study focuses on resolving moderate amounts of crustal motion at the continental scale based on a large volume of global positioning system（GPS） data during 1998e2014. A state-of-the-art GPS processing strategy was used to resolve position time series and velocities from carrier beat phases for all available data. Position time series were closely analyzed to estimate linear constant, coseismic displacements, postseismic motions, and other parameters. We present coseismic offsets inferred from the GPS data for the 2010 Yushu and 2014 Yutian earthquakes, and also illustrate transient postseismic motions following the 2001 Kokoxili, 2008 Wenchuan, and 2011 Tohoku-Oki earthquakes. Since not all GPS position time series dominated by postseismic motions can be modeled and corrected reasonably, we present contemporary horizontal velocities from 2009 to 2014 for campaign stations and from 1998 to 2014 for continuous stations, irrespective of postseismic deformations. Our study concludes that we need to accumulate observations over a greater duration and apply accurate postseismic modeling to correct for transient displacement in order to resolve reasonable interseismic velocity.

Crustal movement and deformation in Taiwan and its coastal area

Based on the station velocity data obtained from Fujian coastal GPS network and Taiwan-Luzon GPS network and the data obtained from IGS permanent stations commonly used in the data processing of both networks, the uniformity of reference frames and velocity fields of both GPS networks is realized. It has been discovered from the analysis on the velocity field in Taiwan and its coastal areas that the horizontal crustal movements in the coastal area of Fujian, Taiwan Strait and the northern part of Taiwan Island are fully consistent. The movement direction is around 26.0E by S and the rate is about 39 mm/a. The opposite variation occurs in the coastal mountain area in the eastern part of Taiwan Island with the movement direction of 30.0N by W and the movement rate of about 33.3 mm/a. In the southern end of Taiwan Island, the movement direction is 50.0S by W and the movement rate is about 13 mm/a. If the geometric center of Fujian coast is used as the reference datum, Taiwan Island has a consistent (except its north end) NW-trending movement with the direction of around 50.0N by W. The maximum rate of 61 mm/a occurs along the eastern coast and decreases gradually towards west. The analysis of strain field indicates that Taiwan and its coastal area have a uniform strain field with the principal compressive strain direction of N48.0W and the principal tensile strain direction of N42.0E. The principal compressive strain rate along the eastern coast of Taiwan Island is 3.43610-7/a, which decreases gradually towards west and reaches 1.86110-8/a to Fujian coast. The collision and underthrust of Philippine Sea plate with Eurasian plate in the eastern part of Taiwan Island can be considered as the principal force for the crustal movement, deformation and great earthquake occurred in Taiwan and its coastal area. The direction of principal compressive stress in the area is about N55.0W.