[1] To characterize the present-day vertical displacement field in the active Taiwan orogenic belt, 1843 precise leveling and 199 continuous GPS measurements from 2000 to 2008 are collected and analyzed in this study. Vertical velocities derived from the leveling data are placed in a reference frame of the Chinese continental margin using continuous GPS observations at nearby sites. The leveling and GPS vertical velocities generally reveal a dome-shaped pattern with uplift of ∼0.2–18.5 mm/yr in the interior of the mountain range and subsidence on the flanks of the mountains and coastal plains. Modern uplift rates in the active fold and thrust belt are generally consistent with geologic uplift rates. However, present-day uplift rates in the Central Range are faster than the million-years-averaged exhumation rates. The modern subsidence rates are generally consistent with geologic rates, except for the rates in western coastal areas due to groundwater pumping. Present-day subsidence in the southern Central Range and northern Coastal Range is, however, inconsistent with long-term uplift, which may reflect interseismic elastic strain accumulation across faults. Present-day subsidence in northern Taiwan occurs in a region of postcollisional orogenic collapse. We model the present-day and geologic vertical velocities and published GPS horizontal velocity data across southern Taiwan using a 2-D lithospheric model. The model suggests a combined slip rate of 40 mm/yr on the frontal thrusts and 45 mm/yr on the Longitudinal Valley fault. The model requires an additional source of crustal thickening under the Central Range to match the observed present-day uplift rates.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2011JB008242

Modern vertical deformation rates and mountain building in Taiwan from precise leveling and continuous GPS observations, 2000–2008

http://basin.earth.ncu.edu.tw/download/courses/seminar_MSc/2011/0112-2_01.pdf

Thirty-year land elevation change from subsidence to uplift following the termination of groundwater pumping and its geological implications in the Metropolitan Taipei Basin, Northern Taiwan

Risk assessment and zoning are very important to risk management. In this study, a land subsidence risk assessment index was proposed based on the Disaster Risk Index. The cumulative subsidence volume, the land subsidence velocity, and the groundwater exploitation intensity were collected, analyzed, and put together to create a land subsidence hazard evaluation map in Tianjin coastal area. The population density, Gross Domestic Product per square kilometer, and construction land proportion were adopted as indexes to create the vulnerability map. In addition, the capability of land subsidence prevention and reduction was also assessed. Finally, the land subsidence risk map was created by combing the hazard, vulnerability, and the capability of land subsidence prevention and reduction map. Specifically, the land subsidence risk was classified into five levels, i.e., very high, high, medium, low, and very low. The result of this research could provide a solid basis for the sustainable development as well as disaster prevention policy-making of Tianjin city.

Risk assessment of land subsidence at Tianjin coastal area in China

https://ir.nctu.edu.tw:443/bitstream/11536/20427/1/000309794100008.pdf

Modeling aquifer-system compaction and predicting land subsidence in central Taiwan

[1] Using data at 110 continuous GPS stations from 1 January 2003 to 31 December 2005, we characterized the surface deformation in Taiwan after the M w = 7.6 Chi-Chi earthquake of 21 September 1999. In continuous GPS (CGPS) data, the maximum coseismic deformation of the Chengkung earthquake and Ilan double earthquakes reached 165.5 ± 0.5 mm and 35.4 ± 0.5 mm in horizontal displacement and 181.7 ± 1.1 mm and 12.6 ± 1.5 mm in vertical displacement, respectively. With respect to Paisha station, S01R, the stations of the Coastal Range and Lanhsu showed an average displacement of 40.5-93.6 mm/yr with directions of307°-333°. The stations in the Longitudinal Valley and Central Range revealed velocities in the range 19.0―49.3 mm/yr with directions of 285°―318°. In western Taiwan, the velocities in the inner fold-and-thrust belt range from 14.2 to 45.5 mm/yr with directions of 284°―304°. Extensional strain affects the Ilan and Pingtung plains near belt tips, revealing lateral extrusion toward the adjacent subduction zones. Extensional strain also affects the southern Central Range because of the rapid uplift related to the southward propagating collision process. Large and medium size earthquakes affect the strain pattern revealed by CGPS, albeit in different ways: regional extension and displacement were large and rotations were small regarding the M w = 7.6 Chi-Chi earthquake. In contrast, the limited size of the affected area, moderate displacement, and large rotations characterized the 2003 M w = 6.8 Chengkung earthquake. The impact of smaller earthquakes such as the 2005 M w = 5.9 Ilan double earthquakes and the 2005 M w = 5.6 Hualien earthquake was locally significant but regionally minor. The CGPS data provide a snapshot of the deformation that is generally consistent with the long-term history of the collision but should not be directly extrapolated because thrust deformation is migrating along the tectonic boundary. Regarding the Chi-Chi earthquake, the new CGPS data show that the Chi-Chi hanging wall is still recognizable as a kinematic block, whereas in the previous pattern the hanging wall was not discemable.

http://www.gl.ntu.edu.tw/geodesy/images/publications/paper/pa58-0.pdf

GPS crustal deformation, strain rate, and seismic activity after the 1999 Chi‐Chi earthquake in Taiwan

The contribution to tectonic subsidence by groundwater abstraction in the Pingtung area, southwestern Taiwan as determined by GPS measurements

Estimation of subsidence using GPS measurements, and related hazard: the Pingtung Plain, southwestern Taiwan

Erosion gullies reflect the incision of bedrock by rivers during the tectonic and topographic evolution of active orogenic zones; however, a limited amount of measurement data is currently available. Therefore, this study explored the incision erosion rate of different lithology in the collapsed surface of a landslide induced by the Chi-chi earthquake in the Tsaoling area of Yunlin County. In this study, we investigated the distribution of erosion gullies produced in different rock formations by the collapsed surface of the Tsaoling landslide based on an openness analysis using a red relief image map (RRIM) and calculated the bedrock incision rate for the Cholan Formation and Chishui Shale for 1999 and 2011, which was 31–39 cm/year and 54–89 cm/year on average, respectively. These results indicated that the Cholan Formation has a higher resistance to erosion than the Chishui Shale, where the erosion was more serious.

Chin-Shyong Hou

Papers

The contribution to tectonic subsidence by groundwater abstraction in the Pingtung area, southwestern Taiwan as determined by GPS measurements

Estimation of subsidence using GPS measurements, and related hazard: the Pingtung Plain, southwestern Taiwan

Using Airborne LiDAR DEM to Determine the Bedrock Incision Rate: An Indirect Dating from Landslide Sliding Surface, Taiwan