Coseismic and postseismic crustal deformations of the Korean Peninsula caused by the 2011 Mw 9.0 Tohoku earthquake, Japan, from global positioning system data

Abstract

Terra Nova, 24, 295–300, 2012 Abstract We present the first analysis on the crustal deformation in the Korean peninsula by the 2011 Tohoku earthquake. The great Mw 9.0 earthquake extended the Korean peninsula along E–W direction even though it is at a distance longer than one thousand kilometres from the epicentre. The coseismic surface displacements from 1.0 cm (in the southwestern part) to 5.4 cm (in the eastern part) were detected by continuous GPS observation. The estimated coseismic strains from the displacements correspond to approximately 6–28 years of accumulated strains in the Korean peninsula. The postseismic displacements during 162 days after the earthquake showed 43–48% of the coseismic displacements. The results imply that the contractional strains of the Korean peninsula have been accumulated by the locked subduction zone off, and a part of accumulated strains has been released by the mainshock and the afterslip of the 2011 Tohoku earthquake.

A geodetic plate motion and Global Strain Rate Model

“…Even though this station is >2000 km from the epicenter, it is likely that this velocity change is due to viscoelastic postseismic relaxation. Similar far-field effects are seen in stations in SE Australia after the 23 December 2004, M w 58.1, Macquarie Ridge earthquake [Tregoning et al, 2013] and in east Asia after the 11 March 2011, M w 59.0 Tohoku-Oki event [Baek et al, 2012;Shestakov et al, 2012]. However, unlike Reddy et al [2010], we do not see an east-ward speed-up for the CGPS station in Hyderabad, 500 km north of Bangalore.…”

“…These transients are often due to postseismic deformation or slow-slip events (where the excluded part of the time series is replaced with an offset). In the extreme, the exclusion could be for periods >10 years, sometimes at stations as far as several thousands kilometers from the largest earthquakes Baek et al, 2012;Shestakov et al, 2012;Tregoning et al, 2013]. An exception is made for stations on the Indian plate, explained in section 4.1.…”

Crustal Deformation of South Korea After the Tohoku‐Oki Earthquake: Deformation Heterogeneity and Seismic Activity

“…Before the Tohoku‐Oki earthquake, velocity vectors in South Korea generally trended about N113°E with an average magnitude of 30 mm/year (the red arrows in Figure ); after the mainshock, the average direction instantly changed to point toward the epicenter (N82°E) with magnitudes of 1.0–54.0 mm (Baek et al, ; Kim et al, ; the used reference frame of these studies is the same as ours; IGS 2008). We analyzed average velocities of two‐year interval to evaluate the time taken for the velocities to change into premainshock values (Table and Figure ).…”

“…There was a significant coseismic surface displacement not only in the Japanese Islands (Nishimura et al, ) but throughout East Asia (up to 3,000 km from the epicenter; Pollitz et al, ; Shestakov et al, ; Wang et al, ). Coseismic and postseismic crustal deformation of South Korea due to the Tohoku‐Oki earthquake, as estimated from Global Positioning System (GPS) data, was dominated by dilatation; that is, either the absolute magnitude of the positive maximum principal straining axis was greater than that of the negative minimum principal straining axis or both the maximum and minimum principal straining axes were positive (Baek et al, ; Kim et al, ). Focal mechanism solutions of earthquakes in South Korea indicate that the dominant type of earthquake faulting was strike slip, while thrust and normal faulting are relatively uncommon (Choi et al, ; Park et al, ).…”

Seismic Velocity Changes in the Backarc Continental Crust After the 2011 Mw 9.0 Tohoku‐Oki Megathrust Earthquake

“…The peak lateral coseismic displacements reached ∼4.3 m in Northern Honshu and 2–5 cm on the Korean Peninsula (Baek et al, ; Hong et al, ; Simons et al, ). Postseismic displacements continued following the coseismic displacements (Kim et al, ; Sun et al, ; Tobita, ).…”