Broad‐band Rayleigh wave tomography of Taiwan and its implications on gravity anomalies

Abstract

We construct the first broad‐band surface wave group velocity dispersion maps for the entire island of Taiwan using the ambient seismic noise tomography. Continuous data from three island‐wide broad‐band networks are used. In particular, taking advantage of the temporary arrays deployed by the TAiwan Integrated GEodynamics Research project (TAIGER), we have collected an unprecedented data amount for the noise tomography in Taiwan. We construct 2D group velocity maps for Rayleigh waves from 4 to 20 seconds using a wavelet‐based multi‐scale inversion technique. Patterns of lateral variations of our shorter period (<10 seconds) model demonstrate very good correlation with the surficial geology, whereas the overall structure, albeit with much better resolution in the shallow depth, is generally consistent with previously established body wave models. Besides seismic structure, our model also provides vital constraint on resolving the long‐lasting controversy about most prominent Bouguer gravity anomaly in central Taiwan, implying that it is likely caused by a deeper mountain root. With regard to various scenarios of the tectonic evolution of Taiwan, our results seem to favor the lithospheric collision model that invokes significant crustal thickening during the collisional orogeny.