Cyclic Upper Lithospheric Collision and Relaxation at the Junction of Collision to Subduction in Northern Hualien, Taiwan
Date Issued
2011
Date
2011
Author(s)
Chen, Kuan-Hsiang
Abstract
Continuous GPS (CGPS) and seismic data from northern Hualien in Taiwan reveal that the convergence between the Eurasian plate and the Philippine Sea plate produces abundant background seismicity and cyclically leading to more seismicity containing larger events with opposite direction of the plate convergence. We discover unusually large horizontal displacement variations of annual east-westward cycle with peak-to-peak more than 30 mm from 15 CGPS time series in northern Hualien. Most stations move eastward during May to October, and move westward during November to April every year. Several studies have shown that CGPS vertical component is typically influenced by seasonal changes of environment factors, and CGPS horizontal components are one-third to one-tenth those of the vertical displacement. We test the perception with newly acquired geodetic and seismological data and found it inadequate for the case of surface displacements in northern Hualien. The evidence for contribution of environment factors in the ground displacements is very weak in this region. We thus calculated the average velocity of northwestern and reversal southeastern motion; the observed displacements are nearly parallel to the direction of subduction of the Philippine Sea plate. The CGPS areal strain also implies high correlation between occurrences of local earthquakes Mw > 5.0 and surface displacements. All observations clearly demonstrate a cycle of the converging and relaxation behaviors of the Eurasian plate and the Philippine Sea plate within the junction of collision to subduction in northern Hualien. As an alternative explanation, the cyclic movement linking to deeper crustal deformation is proposed for the junction area of subduction and collision, instead of the common perception for influence of environmental factors.
Subjects
cyclic motion
junction
crustal strain
seismicity
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-100-R98224204-1.pdf
Size
23.54 KB
Format
Adobe PDF
Checksum
(MD5):b2375046ce5af17f516a1081138a0926