Three‐dimensional P velocity structures of the lithosphere beneath Taiwan from the analysis of TAIGER and related seismic data sets

Abstract

The convergence of the Philippine Sea and the Eurasian plates in the Taiwan region led to the formation of a young collisional mountain between two subduction zones of nearly orthogonal polarities. The geological processes underlying the collision and its relation to subduction are the primary targets of TAIGER (Taiwan Integrated Geodynamic Research) project. Newly acquired passive and active sources data on land, supplemented by ocean bottom as well as permanent seismic network data, are used to derive a new 3‐D tomographic velocity model. Using the 7.5 km/sec contour as a marker for crustal deformation, two trend‐parallel “roots,” one under the Central Range with a maximum depth of 55 km and the other under the Coastal Range at 40 km, are found to extend from southern to central (∼24°N) Taiwan. Between the two roots and lying approximately beneath the Longitudinal Valley, the 7.5 km/sec contour rises to 25 km depth. In the upper mantle, a high velocity zone, east‐dipping and its upper surface coinciding with a Wadati‐Benioff zone in the south (∼22.8°N), becomes near vertical and ill‐defined in the north (∼23.9°N). The crustal deformation as defined by the “roots” and the along‐trend variations of the upper mantle structures under Taiwan provide key information for the orogeny. With the thickening of crust to 55 km or more processes such as eclogitization and delamination may come into play.

On the Use of Explosion Records for Examining Earthquake Location Uncertainty in Taiwan

“…For the positions which were moved southward, the same situation may have resulted due to the differences in the Moho depths. In southern Taiwan, the Moho depth is relatively shallower than that in central-northern Taiwan (Kim et al 2005;Wu et al 2007;Kuo-Chen et al 2012;Ustaszewski et al 2012) indicating that the average velocity in southern Taiwan is higher than that in central-northern Taiwan. Therefore, most of the relocated positions may move southward as well.…”

“…The coastal plains and the mountain regions (Fig. 1) are relatively low and high, respectively (Kim et al 2005;Wu et al 2007Wu et al , 2009Kuo-Chen et al 2012). In such regions, the velocity model we used may not have enough low and high seismic-wave speeds in such regions.…”

“…Recently, the Taiwan Integrated GEodynamic Research (TAIGER) project, a large Taiwan-US cooperative research project, was conducted from 2004 -2009. Scientists from France, Japan, and the Philippines also participated (Kuo-Chen et al 2012). The TAIGER project employed seismological techniques to image the crustal and upper mantle structures beneath mountain belts and surrounding seas in and around the Taiwan region, and explore mountain building processes, plate boundary dynamics, seismogenic mechanisms, and marine geo-hazards.…”

Active tectonics in Taiwan: insights from a 3-D viscous finite element model

“…The model domain is 100 km in depth. The threedimensional lithospheric structure is very complex in Taiwan area (Kim et al 2005;Wu et al 2007;Kuo-Chen et al 2012). In this study, for simplification, the crustal thickness is based on the Crust2.0 model (http://igppweb.ucsd.edu/ *gabi/rem.html), assuming Airy isostasy and using the topography data from ETOPO2v2g (http://www.ngdc.…”

Hybrid Ground Motion Simulation for the 2013 ML 6.4 Ruisui, Taiwan Earthquake

“…In this study our goal is not to obtain the best fit model but to investigate the main source properties and reproduce the overall characteristics of the observed ground motions. Thus, following the fault setting of Lee et al (2014), we used the F-K method (Zhu and Rivera 2002) with a 1D velocity model modified from a 3D velocity model (Kuo-Chen et al 2012) to compute the synthetic Green's functions. Figure 2 shows a comparison of the observed and synthetic acceleration waveforms, both with bandpass filters at 0.08 -0.5 Hz.…”