The underthrusting of continental crust during mountain building is an issue of debate for orogens at convergent continental margins. We report three-dimensional seismic anisotropic tomography of Taiwan that shows a nearly 90° rotation of anisotropic fabrics across a 10- to 20-kilometer depth, consistent with the presence of two layers of deformation. The upper crust is dominated by collision-related compressional deformation, whereas the lower crust of Taiwan, mostly the crust of the subducted Eurasian plate, is dominated by convergence-parallel shear deformation. We interpret this lower crustal shearing as driven by the continuous sinking of the Eurasian mantle lithosphere when the surface of the subducted plate is coupled with the orogen. The two-layer deformation clearly defines the role of subduction in the formation of the Taiwan mountain belt.

A gasoline powered engine installed and operated on an engine dynamometer was used to investigate the reduction in polycyclic aromatic hydrocarbon (PAH) emission and air pollution [CO, hydrocarbons (HCs), NO x ] by using a methanol-containing additive (US Department of Commerce Patent and Trademark Office Certification No. 5688295, 18 November 1997). Mixtures of 25 per cent methanol with 75 per cent 95 lead-free gasoline (LFG), 25 per cent methanol with 75 per cent 92 LFG and 25 per cent methanol with 75 per cent premium leaded gasoline (PLG) were used as the power fuels. The engine was simulated for the idling condition and for cruising engine speeds of 1500, 2000 and 3000 r/min. The concentrations of 21 individual PAHs and air pollutants in the engine exhaust emissions were determined. The experimental results proved that the methanol-containing additive obviously promotes PAH and air pollution reduction, especially at an engine speed of 1500 r/min. The concentration of carcinogenic compounds-benzopyrene (BaP), dibenzanthracene (DBA), indenopyrene (IND) and benzoperylene (BghiP)-found in major vehicle fuels is approximately zero in the methanol-containing additive.