On 11 March 2011, at 05:46:24 UTC, a magnitude 9.0 Mw earthquake occurred near the east coast of Honshu, Japan. The earthquake generated a tsunami with wave heights up to 38.9 m. The earthquake and tsunami caused almost 20,000 deaths and missing in Japan. The tsunami was observed all over the Pacific Ocean and caused additional deaths in Indonesia and California, USA. The earthquake and tsunami also caused the worst nuclear emergency since Chernobyl. The damage costs resulting from the earthquake and tsunami in Japan will be between 16 and 25 trillion yen. The National Geophysical Data Center (NGDC) and co-located World Data Center for Geophysics maintain a global historical event database of tsunamis, significant earthquakes, and significant volcanic eruptions (http://www.ngdc.noaa.gov/hazards/). As of 3 October 2011, NGDC has collected 288 tide gauge observations, 34 Deep-ocean Assessment and Reporting of Tsunami (DART 1 ) and bottom pressure recorder (BPR) station observations, and over 5,000 eyewitness reports and post-tsunami field survey measurements. These data will be useful for understanding and modelling tsunami generation, propagation, and inundation on land.
[1] We report unique deep-sea recordings of the Sumatra tsunami of December 2004 by high-resolution DART® (Deep-ocean Assessment and Reporting of Tsunami) and CORK (Circulation Obviation Retrofit Kit) bottom pressure sensors deployed at depths of ∼1500-3500 m in Cascadia Basin in the northeast Pacific. The simultaneous records from these sites establish the first-ever regional-scale tsunami detection array for the open ocean, enabling us to resolve both seafloor and crustal tsunami signals and to determine fundamental properties of the waves following their 22,000 km journey from the source region. Waves reaching the basin had mean amplitudes of ∼5 mm with energy spread over a broad frequency band from 0.4 to 7 cph. Peak tsunami energy was in the 0.8 to 2 cph (75 to 30 min) band. Leading waves from the event arrived 34-35 h after the earthquake, roughly 7 h later than expected, suggesting that the tsunami mainly propagated by the "most economic" (minimum energy loss) path along mid-ocean ridge wave-guides rather than taking the direct and fastest path across the ocean. Motions within the peak energy band comprise roughly 50% coherent progressive waves propagating from the south at longwave phase speeds of ∼150 ms −1 and 50% random waves scattered from the coast and bottom irregularities. Tsunami amplitudes in the borehole were onethird those on the seafloor. The extensive "ringing" and anomalously slow (3.5-day) e-folding decay time of the tsunami wave energy indicates long duration energy flux radiating from the Indian Ocean via the Southern Pacific Ocean.
In response to the 2004 Indian Ocean tsunami, the United States began a careful review and strengthening of its programs aimed at reducing the consequences of tsunamis. Several reports and calls to action were drafted, including the Tsunami Warning and Education Act (Public Law 109-424) signed into law by the President in December 2006. NOAA's National Geophysical Data Center (NGDC) and co-located World Data Center for Geophysics and Marine Geology (WDC-GMG) maintain a national and international tsunami data archive that fulfills part of the P.L. 109-424. The NGDC/WDC-GMG long-term tsunami data archive has expanded from the original global historical event databases and damage photo collection, to include tsunami deposits, coastal water-level data, DART TM buoy data, and high-resolution coastal DEMs. These data are used to validate models, provide guidance to warning centers, develop tsunami hazard assessments, and educate the public about the risks from tsunamis. In this paper we discuss current steps and future actions to be taken by NGDC/WDC-GMG to support tsunami hazard mitigation research, to ultimately help save lives and improve the resiliency of coastal communities.
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