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

Abstract

In order to provide a detailed vertical velocity field in southernmost Longitudinal Valley where shows a complex threefault system at the plate suture between Philippine Sea plate and Eurasia, we conducted leveling and GPS measurements, compiled data from previous surveys and combined them into a single data set. We compiled precise leveling results from 1984 to 2009, include 5 E-W trending and one N-S trending routes. We calculated the GPS vertical component from 10 continuous stations and from 89 campaign-mode stations from 1995 to 2010. The interseismic vertical rates are estimated by removing the co-and post-seismic effects of major large regional and nearby earthquakes. A stable continuous station S104 in the study area was adopted as the common reference station. We finally establish a map of the interseismic vertical velocity field. The interseismic vertical deformation was mainly accommodated by creeping/thrusting along two east-dipping strands of the three-fault system: the Luyeh and Lichi faults. The most dominant uplift of 30 mm yr-1 occurs at the hanging wall of the Lichi fault on the western Coastal Range. However the rate diminishes away from the fault in the hanging wall. The Quaternary tablelands inside of the Longitudinal Valley reveals uplift with a rate of 5-10 mm yr-1. Outside of the tablelands, the rest of the Longitudinal Valley flat area indicates substantial subsidence of-10 to-20 mm yr-1. Finally, it appears that the west-dipping blind fault under the eastern side of the Central Range does not play a significant role on interseismic deformation with subsidence rate of-5 to-10 mm yr-1 .

Seismogenic strain across the transition from fore‐arc slivering to collision in southern Taiwan

“…(b) Shaded relief map of the area outlined in Figure 6a with configuration of major active faults on land from Chen et al . [] and the zone of inferred strike‐slip offshore based on our analyses shown as pairs of half arrows. Contours of elevation change shown in color (see key).…”

“…Coseismic subsidence during the 2006 Peinan M w 6.7 earthquake was localized in the valley north of Taitung and at the southern termination of the Coastal Range northeast of Taitung [ Chen et al ., ]. Long‐term GPS data from this region processed to remove the effects of the Peinan earthquake [ Chen et al ., ] likewise reveal subsidence localized at the southern end of the Longitudinal Valley and Coastal Range (see orange and red contour lines in Figure b). These data also indicate rapid uplift to the north where ongoing collision is well documented (see blue and purple contour lines in Figure b).…”

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).…”

“…1), which comprises three major active faults, namely the Lichi fault, the Luyeh fault (Yu et al, 1990;Lee et al, 1998;Yu and Kuo, 2001), and the likely blind Central Range fault (Biq, 1965;Lu and Hsu, 1992;Wu et al, 2006;Shyu et al, 2008;Chen et al, 2012). Tectonically, it is located at the suture zone between the Luzon arc of the Philippine Sea plate (i.e.…”