Abstract
ABSTRACTWe focus herein on the location, characterization and the quantification of the most active structural feature of Taiwan: the Longitudinal Valley Fault that corresponds to the suture in between the Philippine and Eurasian Plates. In order to determine and monitor its present inter-seismic deformation, we focus on the Pingting Terraces area, situated in the South Longitudinal Valley (Eastern Taiwan). We first determine the structural geometry issued from both photo-interpretation deduced from new unmanned aerial vehicle (UAV) high-resolution Digital Terrain Model data that we acquired (34.78 km2 with 7.73 cm ground sampling distance), combined with geological field work. In order to characterize and quantify the present deformational patterns over the Pingting terraces, we used an InSAR time series Interferometry algorithm (MT-InSAR) applied to nine L-band SAR images from ALOS satellite acquired over the period 2007–2010. The unprecedented density of measurements (about 120 points per km2 for a total of 6,400 points) gives a continuous overview of the inter-seismic shallow deformation. The structural geometry combined with the mean velocity map (MT-InSAR) reveals two clear active faults situated above the scarps of the Pingting terraces and responsible for up to 7 and 20 mm/yr velocity offset along the radar line of sight. A temporal analysis of the deformation is performed with one measurement at each SAR acquisition date, giving major improvements in the characterization and quantification of the Longitudinal Valley active Fault trace.
Highlights
How to locate, characterize and quantify the active deformation of the southern Longitudinal Valley Fault (LVF) in eastern Taiwan which is the most active tectonic feature of the Taiwan orogen (Figure 1(a))? The Longitudinal Valley is the outcropping active tectonic suture in between the ongoing collision of the continental Eurasian margin and the oceanic and volcanic Philippine Sea plate (e.g. Ho 1986; Angelier et al 1997; Malavieille et al 2002)
It should be interesting to date precisely the remnants of the CoaR Paleo Surfaces (PS: item 6 of Figure 3) revealed by the photo-interpretation of the so precise Digital Terrain Model (DTM) in order to reconstruct the longer term of the neotectonic deformation
Over the Pingting Terraces, the use of both high-resolution topographic data combined with previous geological maps, allow us mapping more precisely the structural geometry of the major suture of the Eurasian/Philippine sea plate collision within the Longitudinal Valley
Summary
Characterize and quantify the active deformation of the southern Longitudinal Valley Fault (LVF) in eastern Taiwan which is the most active tectonic feature of the Taiwan orogen (Figure 1(a))? The Longitudinal Valley is the outcropping active tectonic suture in between the ongoing collision of the continental Eurasian margin and the oceanic and volcanic Philippine Sea plate (e.g. Ho 1986; Angelier et al 1997; Malavieille et al 2002). The Longitudinal Valley is the outcropping active tectonic suture in between the ongoing collision of the continental Eurasian margin and the oceanic and volcanic Philippine Sea plate (b) Active tectonic map of the south Longitudinal Valley (Eastern Taiwan). Barrier & Muller 1984; Chang et al 2000; Huang et al 2008; Chi et al 2014) This area represents a case geomorphic example in Taiwan of super-imposition of active tectonics and river incision within the dark blue, soft and deep-offshore clayey and blocky Lichi Melange (Figure 1). We propose to precise (1) the detailed structural geometry of the place by both using classical photo-interpretation of high-resolution Digital Terrain Model (DTM) acquired through unmanned aerial vehicle (UAV) and validated by field studies, and (2) to determine the activity of the LVF branches by adding information derived by the PALSAR À ALOS1 time series interferometry in between 2007 and 2010
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