Applying Green-function theory to the calculation of flexural rigidity allows to consider relatively high spatial resolution in the order of 50-250 km. The spatial resolution is considerably greater than the one obtainable with the spectral methods. The Green function can be calculated numerically (Braitenberg, et al., 2002, EPSL, 202, 387-404), or analytically (Wienecke, 2006, PhD thesis, 126 pp, FU-Berlin). A geodynamically interesting examples is the Tibet-Qinghai plateau. We present a Moho model and characterise the plateau and surrounding areas in terms of flexural rigidity. The Moho undulations correlate with major suture lines, as the Bangong Nujian Suture (relatively shallow Moho, 65 km). The flexural rigidity is higher for the Tarim and Qaidam basins, with respect to the Tibet plateau. The high rigidity of the Tarim basin explains its lack of seismicity, in contrast to the high tectonic activity in the surrounding areas to the North and South (Braitenberg et al., 2003, EPSL, 205, 211-224). For the South China Sea we model the Moho and basement by using the gravity field derived from altimetry. A sediment thickness and Moho model are included. The basement contains tectonic features, concealed by the sediments and retrievable from gravity inversion. The model crustal thickness values vary between 8 and 12 km and between 10 and 20 km over the oceanic and continental crust of the South China Sea, respectively. The elastic thickness is below 6 km over most of the sea, with lowest values in the margin (between 2 and 4 km). Finally, we invert the gravity data for the gravity-equivalent basement topography, which in sediment- covered areas corresponds to the basement and in sediment-free areas coincides with the bathymetry. We find a continuous ridge structure along the entire mid-basin, changing from a steep valley in the younger SW basin to a less pronounced valley in the NE basin, lined with seamounts. Our model shows the spreading center to be continuous and to bend from the older EW orientation to the younger SW-NE orientation rather than being made up of two separate axis segments.
Geodynamic implications of high resolution flexural rigidity variations-achievements using the convolution method
BRAITENBERG, CARLA;
2006-01-01
Abstract
Applying Green-function theory to the calculation of flexural rigidity allows to consider relatively high spatial resolution in the order of 50-250 km. The spatial resolution is considerably greater than the one obtainable with the spectral methods. The Green function can be calculated numerically (Braitenberg, et al., 2002, EPSL, 202, 387-404), or analytically (Wienecke, 2006, PhD thesis, 126 pp, FU-Berlin). A geodynamically interesting examples is the Tibet-Qinghai plateau. We present a Moho model and characterise the plateau and surrounding areas in terms of flexural rigidity. The Moho undulations correlate with major suture lines, as the Bangong Nujian Suture (relatively shallow Moho, 65 km). The flexural rigidity is higher for the Tarim and Qaidam basins, with respect to the Tibet plateau. The high rigidity of the Tarim basin explains its lack of seismicity, in contrast to the high tectonic activity in the surrounding areas to the North and South (Braitenberg et al., 2003, EPSL, 205, 211-224). For the South China Sea we model the Moho and basement by using the gravity field derived from altimetry. A sediment thickness and Moho model are included. The basement contains tectonic features, concealed by the sediments and retrievable from gravity inversion. The model crustal thickness values vary between 8 and 12 km and between 10 and 20 km over the oceanic and continental crust of the South China Sea, respectively. The elastic thickness is below 6 km over most of the sea, with lowest values in the margin (between 2 and 4 km). Finally, we invert the gravity data for the gravity-equivalent basement topography, which in sediment- covered areas corresponds to the basement and in sediment-free areas coincides with the bathymetry. We find a continuous ridge structure along the entire mid-basin, changing from a steep valley in the younger SW basin to a less pronounced valley in the NE basin, lined with seamounts. Our model shows the spreading center to be continuous and to bend from the older EW orientation to the younger SW-NE orientation rather than being made up of two separate axis segments.Pubblicazioni consigliate
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