Lateral extrusion and tectonic escape in Ilan Plain of northeastern Taiwan
Reporter: Cheng-Wei Shih
Abstract
The Ilan Plain is surrounded by the high mountains of the Hsuehshan Range to the Northwest and the Central Range to the South. It's also considered as a delta fan formed as a back-extension of Okinawa Trough. We analyze the present-day deformation of Ilan Plain in two ways. One is the Taiwan GPS Network which observed the horizontal components of displacement and deformation on the surface. The other is the analysis of focal mechanisms of earthquakes allowed us to determine the nature of seismotectonic regimes in three dimensions. Then we find that the pattern of velocity vectors with a clockwise rotation around the Ilan Plain is approximately compatible with small circle and resembles a particle flow moving towards the southeast. It is said that tectonic extrusion describes the lateral motion of structural units that move toward a weaker domain ( Okinawa Trough ) with respect to the mountain belt ( Hsuehshan Range ). Also, the general displacement towards the ES that affects the Ilan Plain area is strongly influenced by extrusion and lateral escape at the tip of the Taiwan collision zone.
References
Angelier, J., Chang, T.Y., Hu, J.C., Chang, C.P., Siame, L., Lee, J.C., Deffontaines, B., Chu, H.T, Lu, C.Y., Does extrusion occur at both tips of the Taiwan collision belt? Insights fromactive deformation studies in the Ilan Plain and Pingtung Plain regions, Tectonophysics , 125(1-3), 39-72, 2008.
Hou, C. S., Hu. J. C., Chen, Y. G., Chen, C. L., Cheng, L. W., Tang, C. L., Huang, S. H. and Lo, C. H., The crustal deformation of the Ilan Plain acted as a westernmost extension of the Okinawa Trough, Tectonophysics , 4 66, Issues 3-4 , 344-355, 2009.