Eddie N. Bernard

Tsunami science before and beyond Boxing Day 2004.

Tsunami science has evolved differently from research on other extreme natural hazards, primarily because of the unavailability until recently of instrumental recordings of tsunamis in the open ocean. Here, the progress towards developing tsunami inundation modelling tools for use in inundation forecasting is discussed historically from the perspective of hydrodynamics. The state-of-knowledge before the 26 December 2004 tsunami is described. Remaining aspects for future research are identified. One, validated inundation models need to be further developed through benchmark testing and instrumental tsunameter measurements and standards for operational codes need to be established. Two, a methodology is needed to better quantify short-duration impact forces on structures. Three, the mapping of vulnerable continental margins to identify unrecognized hazards must proceed expeditiously, along with palaeotsunami research to establish repeat intervals. Four, the development of better coupling between deforming seafloor motions and model initialization needs further refinement. Five, in an era of global citizenship, more comprehensive educational efforts on tsunami hazard mitigation are necessary worldwide.

Real‐time experimental forecast of the Peruvian tsunami of August 2007 for U.S. coastlines

[1]xa0At 23:41 UTC on 15 August 2007, an offshore earthquake of magnitude 8.0 severely damaged central Peru and generated a tsunami. Severe shaking by the earthquake collapsed buildings throughout the region and caused 514 fatalities. The tsunami resulted in three casualties and a representative maximum runup height of ∼7 m in the near field. The first real-time tsunami data available came from a deep-ocean tsunami detection buoy within 1 hour of tsunami generation. These tsunami data were used to produce initial experimental forecasts within 2 hours of tsunami generation. The far-field forecasts indicated that the tsunami would not flood any of the 14 U.S. communities. Comparison with real-time tide gage data showed very accurate forecasts.

The NTHMP Tsunameter Network

A tsunameter (soo-NAHM-etter) network has been established in the Pacific by the National Oceanic and Atmospheric Administration. Named by analogy with seismometers, the NOAA tsunameters provide early detection and real-time measurements of deep-ocean tsunamis as they propagate toward coastal communities, enabling the rapid assessment of their destructive potential. Development and maintenance of this network supports a State-driven, high-priority goal of the U.S. National Tsunami Hazard Mitigation Program to improve the speed and reliability of tsunami warnings. The network is now operational, with excellent reliability and data quality, and has proven its worth to warning center decision-makers during potentially tsunamigenic earthquake events; the data have helped avoid issuance of a tsunami warning or have led to cancellation of a tsunami warning, thus averting potentially costly and hazardous evacuations. Optimizing the operational value of the network requires implementation of real-time tsunami forecasting capabilities that integrate tsunameter data with numerical modeling technology. Expansion to a global tsunameter network is needed to accelerate advances in tsunami research and hazard mitigation, and will require a cooperative and coordinated international effort.

Direct energy estimation of the 2011 Japan tsunami using deep-ocean pressure measurements

[1]xa0We have developed a method to compute the total energy transmitted by tsunami waves, to the case where the earthquake source is unknown, by using deep-ocean pressure measurements and numerical models (tsunami source functions). Based on the first wave recorded at the two closest tsunameters (Deep-Ocean Assessment and Reporting of Tsunamis (DART)), our analysis suggests that the March 11, 2011 Tohoku-Oki tsunami generated off Japan originated from a 300–400 km long and 100 km wide area, and the total propagated energy is 3xa0×xa01015J (with 6% uncertainty). Measurements from 30 tsunameters and 32 coastal tide stations show excellent agreement with the forecasts obtained in real time. Our study indicates that the propagated energy and the source location are the most important source characteristics for predicting tsunami impacts. Interactions of tsunami waves with seafloor topography delay and redirect the energy flux, posing hazards from delayed and amplified waves with long duration. Seafloor topography also gives its spectral imprint to tsunami waves. Travel time forecast errors are path-specific and correlated to the major wave scatterers in the Pacific. Numerical dissipation in the propagation modeling highlights the need of high-resolution inundation models for accurate coastal predictions. On the other hand, it also can be used to account for physical dissipation to achieve efficiency. Our results provide guidelines for the earliest reliable tsunami forecast, warnings of long duration tsunami waves signals and enhancement of the experimental tsunami forecast system. We apply the method to quantify the energy of 15 past tsunamis, independently from earthquake magnitudes. The small tsunami to seismic radiation energy ratios, and their variability (0.01–0.8%), reinforce the importance of using deep-ocean tsunami data, the direct measures of tsunamis, for estimates of tsunami energy and accurate forecasting.

Modeling of the 2011 Japan Tsunami: Lessons for Near-Field Forecast

During the devastating 11 March 2011 Japanese tsunami, data from two tsunami detectors were used to determine the tsunami source within 1.5xa0h of earthquake origin time. For the first time, multiple near-field tsunami measurements of the 2011 Japanese tsunami were used to demonstrate the accuracy of the National Oceanic and Atmospheric Administration (NOAA) real-time flooding forecast system in the far field. To test the accuracy of the same forecast system in the near field, a total of 11 numerical models with grids telescoped to 2xa0arcsec (~60xa0m) were developed to hindcast the propagation and coastal inundation of the 2011 Japanese tsunami along the entire east coastline of Japan. Using the NOAA tsunami source computed in near real-time, the model results of tsunami propagation are validated with tsunami time series measured at different water depths offshore and near shore along Japan’s coastline. The computed tsunami runup height and spatial distribution are highly consistent with post-tsunami survey data collected along the Japanese coastline. The computed inundation penetration also agrees well with survey data, giving a modeling accuracy of 85.5xa0% for the inundation areas along 800xa0km of coastline between Ibaraki Prefecture (north of Kashima) and Aomori Prefecture (south of Rokkasho). The inundation model results highlighted the variability of tsunami impact in response to different offshore bathymetry and flooded terrain. Comparison of tsunami sources inferred from different indirect methods shows the crucial importance of deep-ocean tsunami measurements for real-time tsunami forecasts. The agreement between model results and observations along Japan’s coastline demonstrate the ability and potential of NOAA’s methodology for real-time near-field tsunami flooding forecasts. An accurate tsunami flooding forecast within 30xa0min may now be possible using the NOAA forecast methodology with carefully placed tsunameters and large-scale high-resolution inundation models with powerful computing capabilities.

Tsunami: scientific frontiers, mitigation, forecasting and policy implications

Tsunamis are an ever-present threat to lives and property along the coasts of most of the worlds oceans. As the Sumatra tsunami of 26 December 2004 reminded the world, we must be more proactive in developing ways to reduce their impact on our global society. This article provides an overview of the state of knowledge of tsunamis, presents some challenges confronting advances in the field and identifies some promising frontiers leading to a global warning system. This overview is then used to develop guidelines for advancing the science of forecasting, hazard mitigation programmes and the development of public policy to realize a global system. Much of the information on mitigation and forecasting draws upon the development and accomplishments of a joint state/federal partnership that was forged to reduce tsunami hazards along US coastlines—the National Tsunami Hazard Mitigation Programme. By integrating hazard assessment, warning guidance and mitigation activities, the programme has created a roadmap and a set of tools to make communities more resilient to local and distant tsunamis. Among the tools are forecasting, educational programmes, early warning systems and design guidance for tsunami-resilient communities. Information on international cooperation is drawn from the Global Earth Observing System of Systems (GEOSS). GEOSS provides an international framework to assure international compatibility and interoperability for rapid exchange of data and information.

The 1987–88 Alaskan Bight Tsunamis: Deep Ocean Data and Model Comparisons

Excellent deep ocean records have been obtained of two tsunamis recently generated in the Alaskan Bight on 30 November 1987 and 6 March 1988, providing the best available data set to date for comparison with tsunami generation/propagation models. Simulations have been performed with SWAN, a nonlinear shallow water numerical model, using source terms estimated by a seafloor deformation model based on the rectangular fault plane formalism. The tsunami waveform obtained from the model is quite sensitive to the specific source assumed. Significant differences were found between the computations and observations of the 30 November 1987 tsunami, suggesting inadequate knowledge of the source characteristics. Fair agreement was found between the data and the model for the first few waves of the 6 March 1988 tsunami. Model estimates of the seismic moment and total slip along the fault plane are also in fair agreement with those derived from the published Harvard centroid solution for the 6 March 1988 event, implying that the computed seafloor deformation does bear some similarity to the actual source.

Tsunami forecast analysis for the May 2006 Tonga tsunami

[1]xa0This study applies tsunami forecast models developed for NOAAs Tsunami Warning and Forecast System to investigate the May 2006 Tonga Tsunami. Inversion of the Deep-ocean Assessment and Reporting of Tsunamis (DART) measurements estimates a tsunami magnitude equivalent to an earthquake moment magnitude of 8.0. The DART-constrained modeling forecasts show good agreement with observations at eight coastal tide stations in Hawaii, U.S. West Coast, and Alaska, including first arrival times, wave periods, wave amplitudes, and decay during the day following the earthquake. The forecast system correctly reproduces the reflected waves from North America and the scattered waves by the bottom topography in the South Pacific, which arrived in the Hawaiian Islands 16 and 18.5 h after the earthquake, respectively. Wavelet analysis of the tsunami waves suggests that harbor and local shelf resonances may be predominantly responsible for the late occurrence of the maximum wave observed in some coastal areas. These results suggest expanding the operational use of the real-time forecast models and demonstrate the applicability of the forecast results for “all-clear” evaluations, search and rescue operations, as well as event and postevent planning. This research highlights the value of high-resolution inundation models in real-time forecasts during a long-duration hazard for coastal communities. It also provides a rigorous and successful test of the performance and accuracy of the forecast models when run in real-time mode.

The U.S. National Tsunami Hazard Mitigation Program: A Successful State–Federal Partnership

The U.S. National Tsunami Hazard Mitigation Program (NTHMP) is a State/Federal partnership created to reduce tsunami hazards along U.S. coastlines. Established in 1996, NTHMP coordinates the efforts of five Pacific States: Alaska, California, Hawaii, Oregon, and Washington with the three Federal agencies responsible for tsunami hazard mitigation: the National Oceanic and Atmospheric Administration (NOAA), the Federal Emergency Management Agency (FEMA), and the U.S. Geological Survey (USGS). In the 7 years of the program it has, 1. established a tsunami forecasting capability for the two tsunami warning centers through the combined use of deep ocean tsunami data and numerical models; 2. upgraded the seismic network enabling the tsunami warning centers to locate and size earthquakes faster and more accurately; 3. produced 22 tsunami inundation maps covering 113 coastal communities with a population at risk of over a million people; 4. initiated a program to develop tsunami-resilient communities through awareness, education, warning dissemination, mitigation incentives, coastal planning, and construction guidelines; 5. conducted surveys that indicate a positive impact of the program’s activities in raising tsunami awareness. A 17-member Steering Group consisting of representatives from the five Pacific States, NOAA, FEMA, USGS, and the National Science Foundation (NSF) guides NTHMP. The success of the program has been the result of a personal commitment by steering group members that has leveraged the total Federal funding by contributions from the States and Federal Agencies at a ratio of over six matching dollars to every NTHMP dollar. Twice yearly meetings of the steering group promote communication between scientists and emergency managers, and among the State and Federal agencies. From its initiation NTHMP has been based on the needs of coastal communities and emergency managers and has been results driven because of the cycle of year-to-year funding for the first 5 years. A major impact of the program occurred on 17 November 2003, when an Alaskan tsunami warning was canceled because real-time, deep ocean tsunami data indicated the tsunami would be non-damaging. Canceling this warning averted an evacuation in Hawaii, avoiding a loss in productivity valued at

Evolution of tsunami warning systems and products.

68M. Copyright Springer 2005