An earthquake with a magnitude of Mw9.0 has occured 130 km east of Honshu, Japan in a depth of ~25 km. This had been the fourth or fifth strongest earthquake to be recorded by instrumental seismology. The quake caused significant destruction to the Honshu Island and triggered a tsunami that destroyed a number of harbours. In some places (Sendai), tsunami heights were reported to exceed 10 m. A tsunami warning has been released for wide parts of the Pacific, but in Hawaii only 1 m was observed, therefore the warnings for the US West Coast have been lowered.
The tsunami warning has now been cancelled. The waves were observed all around the Pacific with wave heights of around 1 – 1.4 m in Hawaii and similar numbers at the US West Coast. Crescent City, however, was hit by a 2.4 m wave. Some damages have been reported, and one person is missing. Most of the Pacific Islands did not suffer waves higher that 1 m.
Honshu Island suffered peak ground accelerations of up to 0.25 g and intensities in the order of VIII (instrumental intensity). Aerial images show devastated land and a huge tsunami wave hitting the coast. Rockfalls and landslides have been caused according to Al-Jazeera and Boston imagery and ground cracks occured widely. Liquefaction appeared as well as slope failure and differential ground settling. Nuclear power plants have been shut down and three meltdowns were reported after four explosions in Fukushima. An Oil refinery was under fire and fires were reported from all over northern Honshu as well as from Tokyo. A good video collection can be found here. The best pictures are as always to be found at Boston.com.
Until now no final information on victims has been confirmed. Japan officials report about 3000 dead and 20000 missing. Yet it’s clear that damages will sum up to hundreds of billions of dollars, causing significant irritation on global stock markets.
Video showing the tsunami to flood Sendai Airport (by Russia today):
USGS has provided a moment tensor solution that clearly shows a subduction event:
The Finite Fault Model provides a 195/14 direction, with up to 17 m of maximum displacement:
This is just incredible. Here’s the USGS surface projection of the slip distribution:
USGS shake map:
Tsunami warning issued by the Japan Meteorological Agency:
Predicted wave heights, map from West Coast and Alaska Tsunami Warning Center:
On 9 March a series of pre-shocks began with an Mw7.2 event only 40 km away from the location of the Mw9.0 event. More events with magnitudes up to M6 followed, three of them at the same day. Most scientists thought that the 7.2 EQ had been the main event followed by aftershocks, but obviously the highest amount of stress has not been released.
Aftershocks map from EMSC:
The Collm seismological observatory of Leipzig University provides live access to their seismograms. Here’s the daily plot from 11 March. The observatory is part of the German Regional Seismological Network and located east of Leipzig. The Geophysical Institute of Leipzig University started instrumental seismology in 1902 and has a complete record since 1923! In 1935, the observatory moved from Leipzig to the Collm because of the increase of anthropogenic noise.
Japan is situated at the Pacific-Eurasia plate boundary, regularly experiencing strong earthquakes. Japan’s population is maybe the best-trained world wide in terms of behaviour during an earthquake and the risks of tsunamis. Seismic building codes count as the strictest world wide. The USGS database lists a huge number of strong events for the last 100 years:
- 1891-10-27: Mino-Owari, Japan – M 8.0 Fatalities 7,273
- 1896-06-15: Sanriku, Japan – M 8.5 Fatalities 27,000
- 1923-09-01: Kanto (Kwanto), Japan – M 7.9 Fatalities 143,000
- 1927-03-07: Tango, Japan – M 7.6 Fatalities 3,020
- 1933-03-02: Sanriku, Japan – M 8.4 Fatalities 2,990
- 1943-09-10: Tottori, Japan – M 7.4 Fatalities 1,190
- 1944-12-07: Tonankai, Japan – M 8.1 Fatalities 1,223
- 1945-01-12: Mikawa, Japan – M 7.1 Fatalities 1,961
- 1946-12-20: Nankaido, Japan – M 8.1 Fatalities 1,330
- 1948-06-28: Fukui, Japan – M 7.3 Fatalities 3,769
- 1964-06-16: Niigata, Japan – M 7.5 Fatalities 26
- 1995-01-16: Kobe, Japan – M 6.9 Fatalities 5,502
- 2003-05-26: Near the East Coast of Honshu, Japan – M 7.0
- 2003-09-25: Hokkaido, Japan Region – M 8.3
- 2003-10-31: Off the East Coast of Honshu, Japan – M 7.0
- 2004-09-05: Near the South Coast of Western Honshu, Japan – M 7.2
- 2004-09-05: Near the South Coast of Honshu, Japan – M 7.4
- 2004-10-23: Near the West Coast of Honshu, Japan – M 6.6 Fatalities 40
- 2004-11-28: Hokkaido, Japan Region – M 7.0
- 2005-08-16: Near the East Coast of Honshu, Japan – M 7.2
- 2005-11-14: Off the East Coast of Honshu, Japan – M 7.0
- 2009-08-09: Near the South Coast of Honshu, Japan – M 7.1
(Data from USGS)
There is a large number of paleoseismological studies from Japan (mainly in Japanese), among them Ishibashi & Satake, 1998, Rikitake, 1998, Okumura, 2001, Yamazaki et al., 2002, and Okamura et al., 2005. Barnes, 2010 deals with Archeoseismology in Japan, Ishibashi, 2004 provides an overview on historical seismology. Tsunami deposits are among others discussed by Nishimura & Miyaji, 1995, Nanayama et al., 2000, Minoura et al., 2001 (see below) and Goto et al., 2010.
Strongest earthquakes since 1900 (from IRIS):
A great graphic from IRIS shows the relative energy released by earthquakes since instrumental seismology (read the comment of Jody below for understanding why this is very important):
Another great graphic by the USGS on strong earthquakes and the seismic moment (thanks to Jody):
Jody from Paleotsunami Travels has quite exciting articles on the Japan event on her blog. She kindly allowed to publish two articles on a paleotsunamis, that occured at the same coast like the 2011 one, but 1150 years ago:
Tsunami source of the unusual AD 869 earthquake off Miyagi, Japan, inferred
from tsunami deposits and numerical simulation of inundation
Satake, K.; Sawai, Y.; Shishikura, M.; Okamura, Y.; Namegaya, Y.; Yamaki, S.
American Geophysical Union, Fall Meeting 2007, abstract #T31G-03
The 869 Jogan earthquake, off Miyagi, produced unusually large tsunamis,
according to a historical document and tsunami deposits. One of the oldest
official documents in Japan reported that about 1,000 people were drowned
from the tsunami in Sendai plain, indicating much larger tsunami than the
1896 Sanriku tsunami (the worst tsunami disaster in Japan caused by a
tsunami earthquakes) or the 1933 Sanriku tsunami (caused by the outer-rise
normal fault event). Our systematic field surveys revealed the distribution
of tsunami deposits in Sendai and Ishinomaki plains. In both plains, the 869
tsunami deposits are identified as sand layers just below the regional
tephra (To-A from Towada volcano in AD 915). In Sendai plain, the tsunami
deposits extend about 1 to 3 km from the coast line at that time, which is
estimated as about 1 km inland of the present coast. In Ishinomaki plain,
the tsunami deposits extend > 3 km from the estimated coast line, which is
about 1-1.5 km inland of the present coast. Multiple sand layers indicate
recurrence of such unusual tsunamis with approximately 1,000 yr interval. We
computed tsunami inundation in both plains from several types of tsunami
source models such as outer-rise normal fault, tsunami earthquakes (narrow
fault near trench axis), interplate earthquakes with fault widths of 50 and
100 km. Comparison of the computed inundation area with the distribution of
tsunami deposits indicates that only an interplate earthquake source with
100 km width (depth range of 20 to 50 km) can reproduce the observed
distribution of tsunami deposits in both Sendai and Ishinomaki plains. This
source (Mw=8.1 to 8.3) is much larger than the anticipated Miyagi-oki
earthquake (M~7.5) with 99% probability in the next 30 year.
The 860 Jogan tsunami deposit and recurrence interval of large-scale tsunami on the Pacific coast of northeast Japan
Minoura, K., Imamura, F., Sugawara, D., Kono, Y. & Iwashita, T. (2001)
Read article here: Article (PDF)