A New Velocity Field from a Dense GPS Array in the Southernmost Longitudinal Valley, Southeastern Taiwan

Abstract

In the southernmost Longitudinal Valley (LV), Taiwan, we analyzed a dense GPS array composed of 10 continuous stations and 86 campaign-mode stations. By removing the effects of the four major earthquakes (one regional and three local) occurred during the 1992 -2010 observation period, we derived a new horizontal velocity field in this area, which then allows better locating the surface traces of the major active faults, including the Longitudinal Valley Fault (LVF) system and the Central Range Fault, and characterizing the slip behaviors along the faults. Note that LVF reveals two sub-parallel strands in the study area: the Luyeh Fault to the west and the Lichi Fault to the east. Based on the results of strain analyses, including dilatation and shear strain, and projected vectors of station velocities across the major faults, we came to the following geological interpretations. During the inter-seismic periods, the surface deformation of the southernmost LV is mainly accommodated by the faulting on the two branches of the LVF; there is very little surface deformation on the Central Range Fault.The Luyeh River appears to act as a boundary to divide the LVF to behave differently to its northern and southern sides. The Lichi Fault reveals a change of slip kinematics from an oblique shearing/thrusting in the north to a nearly pure shearing with minor extension to the south. Regarding the slip behavior of the Luyeh Fault, it exhibits a creeping behavior in the north and a partially near-surface-locked faulting behavior in the south. We interpret that the two strands of the LVF merge together in the northern Taitung alluvial plain and turns to E-W trend toward the offshore area.

Determination of Vertical Velocity Field of Southernmost Longitudinal Valley in Eastern Taiwan: A Joint Analysis of Leveling and GPS Measurements

“…12). Indeed, the GPS interseismic horizontal displacements favor the latter scenario (Chen et al 2011). A recent study taken from bathymetric geomorphic features also suggests a sharp E-W turn of the LVF in the offshore area east of Taitung (O'hara et al 2011).…”

Reducing distance dependent bias in low-cost single frequency GPS network to complement dual frequency GPS stations in order to derive detailed surface deformation field

“…One major advantage of singlefrequency GPS is that the cost of hardware is much 1 Velocity field of the near-fault GPS array in the Taitung area. The left graph shows the vertical velocities (Chen et al, 2012) and the right graph presents the horizontal velocities relative to the ITRF2005 reference frame (Chen et al, 2013). Black lines represent major active faults: Chihshang Fault (1), Lichi Fault (2) Networks of L1 GPS receivers mixed with dualfrequency receivers have been previously proposed and tested in active fault zones and for volcano monitoring systems with encouraging results (Chen, 2001;Roberts, 2002;Rizos, 2002).…”

“…The convergence rate is about 8.2 cm/year, while one-third of horizontal shortening of about 3 cm/year is being absorbed across the southern LV (Yu et al, 1990;Yu and Kuo, 2001). Recent global positioning system (GPS) and precise levelling results from mostly campaign-mode surveys combined with 10 continuously operating reference stations (CORS) indicated that the velocity fields of horizontal and vertical components vary in different faults and in different locations in this area (Chen et al, 2012;Chen et al, 2013) (Fig. 1).…”

What Causes the Common‐Mode Error in Array GPS Displacement Fields: Case Study for Taiwan in Relation to Atmospheric Mass Loading

“…The International GPS Service final orbits and the standard antenna calibration were employed to reduce the effects of the orbit errors and the phase center biases. The GPS Lab processing mitigates the first‐order ionospheric bias by forming the double‐differenced ionosphere‐free linear combination of carrier phase observations (Bos & Spakman, 2003; Chen et al, 2013; Yu et al, 1997).…”

“…We obtain the continuous GPS daily data from the GPS Lab of the Academia Sinica (Chen et al, 2013) that comprises Taiwan's local networks of the Central Weather Bureau, Academia Sinica, and Central Geological Survey. The GPS data are routinely compiled, processed by means of Bernese software, and solved relative to the tectonically stable station (S01R) of Penghu off the west coast (Chang & Chao, 2014; Chen et al, 2013; Yu et al, 1997). The International GPS Service final orbits and the standard antenna calibration were employed to reduce the effects of the orbit errors and the phase center biases.…”