New Study Now Quantifies the "Huge" Seafloor Movement in 2011 Japanese Earthquake

At a magnitude of 9.0, the earthquake off the Japanese coast last March was already known as one of the most powerful ever recorded, killing (in large part due to the ensuing tsunami) almost 16,000 people and damaging or destroying more than 125,000 buildings. A recent study (available here; subscription required) now quantifies just how monumental the event was: the seafloor in the Japan Trench northeast of the mainland, where the quake originated, was jolted 50 meters horizontally and 10 meters vertically–movement that was “abnormally, extraordinarily huge,” according to Toshiya Fujiwara of the Japan Agency for Marine-Earth Science and Technology.
Fujiwara led the research that used multibeam bathymetric surveys to measure the depth of the water and contouring of the seafloor. He noted that the research team did not expect to be able to use such equipment to detect the crust movement,which during most earthquakes occurs in scales of millimeters or centimeters. For example, the 2005 Miyagi earthquake, which had a magnitude of 7.2, registered a crustal shift of 10 centimeters at a geodetic station near the Japan Trench. The 2011 earthquake had a shift of 15 meters at the same station. The study also found another vertical shift of at least 4-6 meters of a slab of ocean crust between the Japan Trench and the Japanese coastline, which may have contributed to the pulsating pattern of the tsunami waves that eventually struck the country.
The researchers believe that the fault that caused the quake may extend as far as the axis of the Japan Trench.
“Previously, we thought the displacement stopped somewhere underground,” Fujiwara said, “but this earthquake destroyed the entire plate boundary.”
As we posted previously, a number of presentations at the AMS Annual Meeting in New Orleans will cover the community response to the earthquake and tsunami, including Junichi Ishida of the Japan Meteorological Agency who will discuss the earthquake’s impact, the JMA’s response to it, and lessons learned from the disaster in the keynote address for the 28th Conference on Interactive Information Processing Systems (Monday, 11:00 a.m., Room 356).

The Services Response to the Tōhoku Disaster a Focus of the 2012 AMS Meeting

The science ministry in Japan reported last week that more than 30,000 square km–eight percent of the country–is contaminated by radioactive caesium from the Fukushima nuclear plant disaster that stemmed from the Tohoku earthquake and tsunami in March. The radiation was washed out of the skies by rain and snow. As much as four-fifths of the caesium ended up in the ocean–much of it having blown northeastward toward Alaska–and currents carried it to the U.S. coastal waters within a week of reactor releases. By one week later some of the micron-sized particles had traveled around the world.
Because the geophysical dimensions of the earthquake-tsunami-meltdown last March are evident in so many ways, so are the demands it placed on scientific services–from the warnings of giant waves to forecasts of tainted precipitation and groundwater to modeling global ocean currents. Not surprisingly, the disaster literally redefined the job of the Japanese Meteorological Agency.
On the first day of full sessions at the upcoming 2012 AMS Annual Meeting in New Orleans, the epic Tōhoku cataclysm will be discussed from numerous angles, particularly the premium it put on enhanced operational response. “The earthquake and tsunami increased vulnerabilities to meteorological disasters such as sediment disasters, flood, and inundations, in the affected area, by shaking and loosening the soils and damaging the embankments and drainage facilities,” notes JMA’s Junichi Ishida.
Ishida’s presentation is the special keynote address of the Interactive Information Processing Systems (IIPS) conference (11 a.m. Monday, 23 January, Room 356). Ishida will talk about how JMA took increased vulnerabilities into account, by

  • changing criteria for heavy rain warnings to account for runoff and landslide vulnerabilties
  • lowering criteria for coastal inundation warnings (the earthquake actually lowered coastal ground levels, changing tidal configurations)
  • introduced extreme temperature warnings to account for reduced electricity capacity
  • enhanced aviation support (in particular due to traffic for relief flights) because of flight dangers including radioactive clouds

11 March Tsunami sweeps through Sendai Airport, where waters reached the second level of buildings, destroying key operations equipment, scattering mud and debris, and stranding more than a thousand people for two days. The airport eventually reopened as a hub of relief work. Photos copyright Japan Meteorological Agency, with thanks to Junichi Ishida, who will deliver the IIPS conference keynote at the 2012 AMS Annual Meeting.

At the same time (11 a.m. Monday, in Room 338) Yukio Masumoto of the Japan Agency for Marine-Earth Science and Technology will kick off a session devoted to the March 2011 disaster as part of the Coastal Environment symposium. Masumoto will speak about ocean dispersion of radioactive Caesium-137 and Iodine-131 after the Fukushima releases, including relationships with tides, surface winds and, in one case study, atmospheric fallout. In his abstract, Masumoto reports, “In the near-shore region, the wind forcing is a dominant factor that controls the flow field, while large-scale currents and eddies advect the radionuclides in the off-shore region.”
Several other Monday morning presentations in the Coastal Environment session feature rapid American responses last spring to adapt and construct viable modeling systems to depict Japan’s waterborne radiation hazards–speakers include Ronald Meris of the Defense Threat Reduction Agency, William Samuels of Science Applications International Corp (SAIC), and  Matthew Ward of Applied Science Associates.
After lunch, in the same session (2 p.m., Room 338) Gayle Sugiyama of Lawrence Livermore National Laboratory will talk about how the U.S. Department of Energy’s National Atmospheric Release Advisory Center provided analyses and predictions of the radioactive plume, estimating the exposure in both Japan and the United States. Guido Cervone of George Mason University (2:15 p.m., Room 338) will show how dispersion modeling helped reconstruct the otherwise unknown sequence of radioactive releases at the Fukushima nuclear plant. Masayuki Takigawa  (1:45 p.m., Room 338) will discuss results from regional transport modeling of the radioactivity dispersion on land and ocean, while Teddy R. Holt of the U.S. Naval Research Laboratory will show passive tracer modeling capabilities with the Fukushima events in a coupled ocean-atmosphere mesoscale modeling system (1:30 p.m., Room 338).
In a parallel session of the Coastal Environment Conference next door (1:45 p.m., Room 337) Nathan Becker of NOAA/NWS will discuss calculations of detection times for various configurations of the sensors for the Pacific tsunami warning system, concluding that, “for global tsunami hazard mitigation the installation of about 100 additional carefully-selected coastal sea-level gauges could greatly improve the speed of tsunami detection and characterization.”
Interestingly, Monday’s Space Weather posters (2:30 p.m.-4 p.m., Hall E) include a presentation by Tak Cheung of the ionospheric disruptions caused by the great Japanese earthquake last March. Forecasts of ionospheric disturbances affect yet another service in the wake of the disaster: the communications provided by shortwave radio operators. And that will be a topic for Kent Tobiska (Utah State Univ.) in the Space Weather session at 5 p.m. (Room 252/253