The M9.0 2011 Tohoku-oki Earthquake

(March 11, 2011)


The largest earthquake in the Japanese history occurred off the Pacific coast of northeastern Japan at 5:46 am on March 11, 2011 (UT). The earthquake was scaled as M9.0, the 2nd largest earthquake in the 21th century following the 2004 Sumatra-Andaman earthquake (M9.1). The earthquake caused a devastating tsunami and the coastal area was heavily damaged. Such a large earthquake was not expected in the governmental long-term forecast although geologists have recently found various evidence of great tsunami in A.D. 869. Even so, the slip amount of 20-30m estimated based on seismological as well as geodetic analyses is difficult to explain since there have been many M7 class earthquakes in the source region. Significant amount of slip-deficit is need to be carried over occurrences of M7 earthquakes.

In this page, I present some of my GPS data analysis result. Time series plots are automatically updated with a latency of 3days. (Last updated 2011.3.30)

(Left) Coseismic crustal deformation obtained by re-analysis of GEONET GPS data. Maximum horizontal displacement of 5.4m as well as subsidence of 1.1m was detected at Ojika (0550) site. (Right) Postseismic deformation during March 11-19.

Kinematic GPS analysis of IGS MIZU (Mizusawa) with respect to IGS USUD (Usuda) site. Data analysis with Bernese GPS Software Ver. 5.0 and IGS final orbit. 

Kinematic GPS analysis of GEONET 0550 (Ojika) with respect to IGS USUD (Usuda) site on DOY068 (March 9), 2011. We can see an eastward offset of ~2cm caused by the M7.3 foreshock around T=330 sec. Oscillatory fluctuations are mainly caused by multi-path effect (Sidereal filtering is not applied). There is no sign of accelerating displacement toward the main shock on March 11 (Please refer to the time series obtained by static analysis shown below). Data analysis with Bernese GPS Software Ver. 5.0 and IGS final orbit. 

GPS coordinate Time Series (daily updated)

Here are links to coordinate time series plots. We can clearly see ongoing postseismic deformation around the main shock source region. For the location of each station, please refer to the map below.

0016 (Shizunai)  0017 (Setana)     0018 (Muroran)    0027 (Kuji)

0030 (Oga-1)     0032 (Sakata)     0033 (Shinjo)     0036 (Onagawa)

0040 (Yamato)    0041 (Iwaki)      0046 (Omachi)     0112 (Onbetsu)

0120 (Shakotan)  0129 (Kyogoku)    0133 (Biratori)   0134 (Nakasatsunai)

0136 (Tomakomai) 0144 (Samani)     0152 (Rokkasho)   0156 (Hachinohe)

0161 (Iwate)     0166 (Yahaba)     0173 (Kurikoma)   0175 (Shizugawa)

0177 (Taiwa)     0179 (Watari)     0188 (Kawabe)     0192 (Chokai)

0197 (Oguni)     0201 (Namie)      0216 (Mito)       0219 (Utsunomiya)

0220 (Katashina) 0221 (Tsumagoi)   0227 (Maruyama)   0231 (Awashimaura)

0276 (Iida)      0516 (Mikasa)     0534 (Imabetsu)   0540 (Hirosaki)

0546 (Sumita)    0550 (Ojika)      0563 (Tateiwa)    0568 (Sumon)

0570 (Itoigawa)  0581 (Satomi)     0583 (Ishige)     0585 (Nasu)

0602 (Aogashima) 0619 (Hagiwara)   0794 (Assabu)     0796 (Isawa)

0799 (Nishikawa) 0805 (Suibara)    0845 (Koriyama)   0894 (Kazamaura)

0902 (Towadako)  0922 (Takanosu)   0936 (Fukushima)  0958 (Otaki)

3001 (Sano)      3015 (Daiei)      3019 (Koganei)    3022 (Choshi)

3033 (Chosei)    3036 (Futtsu)     3038 (Gotenba)    3074 (Shizuoka)

3099 (Horai)     5113 (Hachijo)

All time series are calculated using Bernese GPS Software Ver.5.0 with IGS rapid orbit, regarding 0123 (Kamishihoro) to be fixed. Large symbols are daily solution. Small symbols connected with lines are 3-hour solutions (for limited time period).

copyright © 2011 Takeshi Sagiya