Crustal Deformation in Central Asia From GPS Measurements, 1994-2002
Abstract
We present Global Positionning System (GPS) measurements of crustal motions at ~50 sites in central Asia (Mongolia-Baikal) for the 1994-2002 period. We investigate the effect of the definition of rigid Eurasia in the implementation of the reference frame and analyze the kinematics of deformation in the northern part of Asia, in particular the motion of north China with respect to Eurasia and south China. In Mongolia, we find rapid spatial changes in strain regime, from NS shortening and right-lateral shear in the Altay, to left-lateral shear in central Mongolia, and to NW-SE extension in Eastern Mongolia and the Baikal rift zone. We find that extension is not limited to the Baikal rift zone, currently opening at 4 mm/yr in a NW-SE direction, but affects a much broader area encompassing most of Eastern Mongolia and, possibly, part of north China. We find that central Mongolia (western part of Amurian-North China block) is moving to the east to southeast at 3-6 mm/yr w.r.t. Eurasia. This is significantly faster than proposed by most deformation models of Asia and 90 degrees off in azimuth, but consistent with other geodetic results in northern China. We model the postseismic effects of four M8 and greater earthquakes that occurred in Mongolia between 1905 and 1957 and show that the present-day contribution of viscoelastic relaxation is less than 3 mm/yr. The discrepancy between GPS observations in Mongolia and model predictions must be sought in processes not accounted for in most of these models, such as the far-field contribution of the Pacific subduction zones and/or the effect of gravitational forces on intracontinental deformation.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.G12C..02V
- Keywords:
-
- 1208 Crustal movements: intraplate (8110);
- 1243 Space geodetic surveys;
- 8155 Plate motions: general;
- 9320 Asia