Presenter: Pei-Cheng Wu
Date: 2015/12/31
Abstract
The Ilan Plain in the northeastern Taiwan is surrounded by the high mountains and the western tip of the Okinawa Trough, the back-arc basin of the Ryukyu subduction zone. It also is the largest known productive geothermal area in Taiwan. To delineate the geothermal structure in this area, a geomagnetic survey was performed in 1978. The existence of a magma chamber in the shallow crust and shallow intrusive igneous rock results in the high heat flow and geothermal gradient. Furthermore, the NE deep fault system within the meta-sandstones provides meteoric recharge from a higher elevation to artesian ally drive the geothermal system. On the other hand, to analyzed the present-day surface deformation of the Ilan Plain and tried to find the relationship with the regional tectonics, Persistent Scatterers InSAR (PSI) had been used to reveal surface vertical displacements, which indicate that there is an area of active subsidence (∼18 mm/yr) located in the southern part of the plain in probable connection with active basement faults and in agreement with previous geodetic measurements and existing geophysical data. The PSI results show that the subsidence occurred in the south of the Ilan Plain. It implies that the opening of the Ilan Plain may have a differing mechanism compared to the Okinawa Trough. Combine the result of geomagnetic survey and PSI, it had been better known about the feature and pattern of active fault in Ilan Plain.
Reference
Tong, L.T., S., Ouyang, T.R., Guo, C.R., Lee, K.S., Hu, C.L., Lee, C.J., Wang(2008) Insight into the geothermal structure in Chingshui, Ilan, Taiwan. Terr. Atmos. Ocean.Sci. 19 (4), 413–424.
Kang, C. C., C. P. Chang, L. Siame, and J. C. Lee (2015) Present-day surface deformation and tectonic insights of the extensional Ilan Plain, NE Taiwan. J. Asian Earth Sci., 105, 408-417, doi: 10.1016/j.jseaes.2015.02.013.