Crustal Structure In Central And Northern Taiwan From Receiver Functions
Taiwan is the type-example of arc-continent collision, with the Luzon Arc on the oceanic Philippine Sea Plate (PSP) colliding with the continental margin of the Eurasian Plate (EUP). In this three-dimensionally complex convergence zone, the PSP subducts to the north beneath the EUP off of northeastern Taiwan, while the EUP subducts to the east beneath the PSP in central and southern Taiwan. The resulting accretion of the Philippine arc crust to the Eurasian continental margin exemplifies an important process in the growth of continents, yet the geometry and structure of the lithosphere at depth are poorly constrained. Some models of the Taiwan orogen propose that thin-skinned deformation above a basal décollement is the dominant deformational style, while other models suggest lithospheric-scale deformation and crustal thickening. This study, conducted as part of the TAiwan Integrated GEophysical Research (TAIGER) project, uses P and S wave receiver functions calculated from teleseismic earthquake data recorded at 30 broadband seismic stations deployed across northern and central Taiwan to detect lithospheric structure and further constrain the style of deformation at the Taiwan orogen. P wave receiver functions suggest the presence of a detachment fault in western central Taiwan continuing eastward from the Western foothills through the Hsueshan Range, and past the Lishan Fault into the Western Central Range. In central Taiwan, P and S wave receiver functions indicate that the crust thickens to the east, with estimated Moho depths increasing from approximately 29 km on the western coast to ~50 km beneath the Central Ranges. On the western coast of northern Taiwan, receiver functions yield an estimated Moho depth of approximately 23 km, with Moho depths increasing to ~40 - 45 km beneath north-central Taiwan. S wave receiver functions indicate that the depth to the base of the Eurasian slab beneath central Taiwan increases from ~100 km beneath the Coastal Plain in the west to ~165 km beneath central Taiwan. The base of the PSP lithosphere beneath eastern central Taiwan is estimated at ~120 km. These new estimates of crustal structure imply thinskinned deformation above a crustal-scale detachment in western Taiwan, with a transition to thicker crust and thick-skinned deformation in central and eastern Taiwan beneath the Hsueshan and Central Ranges.
Taiwan; Receiver Function; Crustal Structure
Brown, Larry Douglas
Allmendinger, Richard Waldron
M.S. of Geological Sciences
Master of Science
dissertation or thesis