中研院地球科學研究所 - 地殼變形研究室
IES, Academia Sinica - Crustal Deformation Observatory


Introduction

About us

The IES has started to observe the horizontal and vertical crustal deformation in the Longitudinal Valley area of eastern Taiwan using traditional geodetic instruments, the electronic distance meter (EDM) and precise level since 1981. A high shortening rate of about 30 mm/yr and a creeping zone at shallow depth are discovered on the Longitudinal Valley Fault which is a suture zone between the Eurasian Plate and the Philippine Sea Plate. Then taking advantage of the newly developed Global Positioning System (GPS) survey technique, an island-wide "Taiwan GPS network" was established in 1989 and the first survey was carried out by IES in March 1990. The GPS has opened a new era for crustal deformation study in Taiwan. A convergence rate of more than 80 mm/yr across the Taiwan mountain belt and strain accumulation associated with active faults are derived from GPS observations in the past decade. The results provide important information for the researches on plate motion and active tectonics.

Over the five-year period after the 1999 Chi-Chi earthquake, a dense "Taiwan Continuous GPS Array" was set up through a joint effort of the Central Weather Bureau (CWB) and IES. In the event of a major earthquake, the preseismic, coseismic, and postseismic deformations can be more precisely determined. Furthermore, in collaboration with the Department of Terrestrial Magnetism, Carnegie Institution of Washington (CIW), a high sensitivity borehole strainmeter array composed of 11 sites has been established in eastern Taiwan since 2003. An integrated network of borehole strainmeter and GPS would provide critical insights into a whole spectrum of tectonic motions such as the earthquake nucleation process, precursory strain changes before, during, and after earthquakes, slow earthquake and slow slip event, as well as seismic and strain budgets over a seismic cycle.