|
Journal: |
Journal of Geophysical Research 2019 No.6
clicks:253 |
|
Title:
|
|
|
Author:
|
C. Honsho1 , M. Kido2 , F. Tomita3 , and N. Uchida1 |
|
Adress: |
|
|
Abstract:
|
One of the important issues on the GPS‐acoustic (GPS‐A) observation for sea bottom
positioning is how to address the horizontal heterogeneity of the sound speed in oceans. This study
presents an analysis method of GPS‐A data in the presence of a sloping sound speed structure. By applying
this method and revising the analysis scheme to make full use of existing data, we reevaluated the
horizontal postseismic deformations occurring ~1.5–5 years after the 2011 Tohoku earthquake. The revised
horizontal movements have more uniform directions and rates between neighboring sites, suggesting
enhancement of the array positioning accuracy. The revised displacement rate of the site on the incoming
Pacific plate, located ~100 km northeast of the main rupture zone, was decreased significantly; it was only
slightly, by 1.4 cm/year larger than the global motion of the Pacific plate, suggesting a relatively small
effect of viscoelastic relaxation. The horizontal movements of the near‐trench sites above the main rupture
zone were generally landward and were significantly faster than the Pacific plate motion, indicating a
viscoelastic relaxation of 5–10 cm/year. The distribution of the fast landward movements peaked near 38°N
at an updip of the mainshock hypocenter and extended significantly farther to the north than to the south.
This implies the existence of a secondary coseismic slip patch in the northern area in addition to a
primary slip patch at ~38°N. The occurrence of episodic slow slip in early 2015 to the north of the main
rupture zone was also verified from the GPS‐A analyses. |
|
Comment: |
|
|
|
|
