Controls of inherited continental margin architecture on the deformation and kinematics of orogenic wedges in arc-continent collisions
The aim of this project is to determine the effect that previous architecture of a continental margin (morphology, structure, rheology) imposes on the early structural evolution of an orogenic wedge. In particular, to determine the variations that these elements of the continental margin (e.g., the change from the platform to the slope, or changes in extensional basins) have on the geodynamics of the orogen and if they predetermine the subsequent structure of the mountain belt. The study area is located in Taiwan, a region that is undergoing active oblique arc-continent colision between the Luzon Arc and the continental margin of Eurasia. In particular, in the south of Taiwan the continental margin is oblique to the trend of the orogen. This disposition provides an exceptional natural example in which to undertake our study since it provides a transect from the platform in the north to the slope in the south. Furthermore, the large amount of seismicity in the region provides a unique data set that allows us to use earthquake hypocenter locations to map faults at depth and provides data for local seismic tomography. Our group has access to the data from some 900 seismic stations in Taiwan. The results obtained by the project will aid in the study of mountain belts worldwide, including Spain, by helping to identify the causes of structural inheritance related to the different parts of a continental margin. Also, it could help in identifying hazardous faults in active orogens. This project will further develop, and enhance on, an earlier project (CGL2009-11843-BTE). The expected results can be divided into four groups; 1) Determination of the 3D structure and kinematics of the frontal part of the mountain belt in southern Taiwan; a region that includes a basementinvolved trust system. The project has a large component of field studies that will focus on detailed structural analyses. 2) Characterise the deep structure of the mountain belt by intergration of the field data with geophysical data including; seismicity, P- and S-wave tomography, gravity, and magnetism. To achieve this, we will model potential field data, and continue to work with our Taiwanese colleauges on seismicity studies and developing new, higher resolution tomographic models. 3) Determination of earthquake fault plane solutions, from which the P, T, and B axes and the horizontal stress will be calculated for the study area. This will provide information on the kinematics of the fault systems and on the state of stress in the deforming slope of the continental margin. 4) Develop models for the geodynamic processes and the tectonic evolution of the area and its application to other orogens worldwide, especially áreas in which the Spanish group has previously worked, such as the Iberian Massif, the Dominican Republic and the Uralides. For this proposal, these processes include, but are not restricted to; a) how the continental crust (in particular the thinned, slope area) deforms as it arrives at an oblique collision zone, b) what the importance is of pre-existing faults and the inversion of sedimentary basin on the structural and kinematic evolution of the orogen, and in the distribution of sesimic activity, and c) what effect the change from the platform area of the margin to the slope has on the structural/kinematic development of the thrust wedge.