Search

The prevailing complex geological and ecological conditions of Taiwan have drawn considerable attention from various geo-ecological communities because of their vulnerability to produce various natural hazards at different scales. Located in the tropical/subtropical zone of the Pacific Rim, its ecological and rugged mountainous properties are environmentally sensitive making monitoring and observation especially difficult because of the high population density. In this article, we have investigated the land deformation in two adjacent industrial parks, Jhong-Li and Guei-Shan, in northern Taiwan using radar interferometry. The Interferometric Synthetic Aperture Radar technique for processing a series of data sets was first validated by comparison with ground levelling measurements over a test site. Excellent agreement was obtained in both deformation pattern and magnitude of subsidence rate. The period of observation dated from 1993 to 2000 with Synthetic Aperture Radar images from ERS-1 and ERS-2. The results, after least-squares adjustment, revealed that the maximum subsidence reached 10 cm and the subsidence rates were about 1.8 cm year−1 (at epicentres) since 1993 at both parks. It was also found that the subsidence rate slowed down after 1998 at Jhong-Li park while continuing at Guei-Shan park. This was strongly associated with local groundwater extraction activities. [ABSTRACT FROM AUTHOR]

Uncertainties in the length of active faults and the styles of deformation often hamper the evaluation of seismic potentials in a region. In the area near Chiayi City of southwestern Taiwan, where historically there have been many strong earthquakes, complex fault and fold systems produced by regional tectonic forces and the subsequent deformation are frequently obscured by vegetation and anthropogenic effects; and therefore detailed deformation information has not been available for evaluation of the seismic potential. By stacking the results from Differential Interferometry and removing the ambiguity of interferograms using GPS data, we were able to retrieve surface deformation information about the area under consideration near Chiayi City. In our results, we found that the Meishan fault to the north of Chiayi City extended 10 km to the west of its currently documented area and served as a geological boundary separating the northern part, where sediments were thicker, from the southern part of the westward extension of the Meishan fault. Chiayi City was under active deformation by a double plunging fold with vertical uplift rate at approximately 1 cm/yr. Frequent seismicity and active deformation allowed the tectonic stress to permute between strike–slip and thrust in this area. Continuous folding of Chiayi City and episodic large earthquakes along the Meishan Fault posed a serious threat of seismic hazards in this region, and called for continuous monitoring of the area. [Copyright &y& Elsevier]