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The December 26, 2004 tsunami was perhaps the most devastating tsunami in recorded history, causing over 200,000 fatalities and widespread destruction in countries bordering the Indian Ocean. It was generated by the third largest earthquake on record (Mw=9.1–9.3) and was a truly global event, with significant wave action felt around the world. Many measurements of this event were made with seismometers, tide gauges, global positioning system stations, and a few satellite overpasses. There were numerous eyewitness observations and video digital recordings of coastal tsunami impact, as well as subsequent coastal field surveys of runup and flooding. A few ship-based expeditions also took place in the months following the event, to measure and map seafloor disturbances in the epicenter area. Based on these various data sets, recent seismic analysis estimates of rupture propagation speed, and other seismological and geological constraints, we develop a calibrated tsunami source, in terms of coseismic seafloor displacement and rupture timing along 1,200 km of the Andaman–Sunda trench. This source is used to build a numerical model of tsunami generation, propagation, and coastal flooding for the December 26, 2004 event. Frequency dispersion effects having been identified in the deep water tsunami wavetrain, we simulate tsunami propagation and coastal impact with a fully nonlinear and dispersive Boussinesq model (FUNWAVE). The tsunami source is specified in this model as a series of discrete, properly parameterized, dislocation source segments [Okada, 1985, Bull. Seismol. Soc. Am., 75(4), 1135–1154], triggered in a time sequence spanning about 1,200 s. ETOPO2’s bottom bathymetry and land topography are specified in the modeled ocean basin, supplemented by more accurate and denser data in selected coastal areas (e.g., Thailand). A 1 min grid is used for tsunami simulations over the Indian Ocean basin, which is fine enough to model tsunami generation and propagation to nearshore areas. Surface elevations simulated in the model agree well, in both amplitude and timing, with measurements at tide gauges, one satellite transect, and ranges of runup values. These results validate our tsunami source and simulations of the December 26, 2004 event and indicate these can be used to conduct more detailed case studies, for specific coastal areas. In fact, part of the development of our proposed source already benefitted from such regional simulations performed on a finer grid (15 s), as part of a Thailand case study, in which higher frequency waves could be modeled (Ioualalen et al. 2007, J. Geophys. Res., 122, C07024). Finally, by running a non-dispersive version of FUNWAVE, we estimate dispersive effects on maximum deep water elevations to be more than 20% in some areas. We believe that work such as this, in which we achieve a better understanding through modeling of the catastrophic December 26, 2004 event, will help the scientific community better predict and mitigate any such future disaster. This will be achieved through a combination of forecasting models with adequate warning systems, and proper education of the local populations. Such work must be urgently done in light of the certitude that large, potentially tsunamogenic, earthquakes occur along all similar megathrust faults, with a periodicity of a few centuries. [ABSTRACT FROM AUTHOR]

Large scale, three-dimensional, laboratory experiments are performed to study tsunami generation by rigid underwater landslides. The main purpose of these experiments is to both gain insight into landslide tsunami generation processes and provide data for subsequent validation of a three-dimensional numerical model. In each experiment a smooth and streamlined rigid body slides down a plane slope, starting from different initial submergence depths, and generates surface waves. Different conditions of wave nonlinearity and dispersion are generated by varying the model slide initial submergence depth. Surface elevations are measured with capacitance gauges. Runup is measured at the tank axis using a video camera. Landslide acceleration is measured with a microaccelerometer embedded within the model slide, and its time of passage is further recorded at three locations down the slope. The repeatability of experiments is very good. Landslide kinematics is inferred from these measurements and an analytic law of motion is derived, based on which the slide added mass and drag coefficients are computed. Characteristic distance and time of slide motion, as well as a characteristic tsunami wavelength, are parameters derived from these analyses. Measured wave elevations yield characteristic tsunami amplitudes, which are found to be well predicted by empirical equations derived in earlier work, based on two-dimensional numerical computations. The strongly dispersive nature and directionality of tsunamis generated by underwater landslides is confirmed by wave measurements at gauges. Measured coastal runup is analyzed and found to correlate well with initial slide submergence depth or characteristic tsunami amplitude. [ABSTRACT FROM AUTHOR]

Based on numerical simulations presented in Part I, we derive predictive empirical equations describing tsunami generation by submarine mass failure (SMF) that are only valid in the vicinity of the tsunami sources. We give equations for slides and slumps, along with some cautions about their appropriate use. We further discuss results obtained here and in Part I and their practical application to case studies. We show that initial acceleration is the primary parameter describing SMF center of mass motion during tsunami generation. We explain an apparent paradox, raised in Part I, in slump center of mass motion, whereby the distance traveled is proportional to shear strength along the failure plane. We stress that the usefulness of predictive equations depends on the quality of the parameters they rely on. Parameter ranges are discussed in the paper, and we propose a method to estimate slump motion and shear strength and discuss SMF thickness to length values, for case studies. We derive the analytical tools needed to characterize SMF tsunami sources in propagation models. Specifically, we quantify three-dimensional (3D) effects on tsunami characteristic amplitude, and we propose an analytical method to specify initial 3D tsunami elevations, shortly after tsunami generation, in long wave tsunami propagation models. This corresponds to treating SMF tsunami sources like coseismic displacement tsunami sources. We conduct four case studies of SMF tsunamis and show that our predictive equations can provide rapid rough estimates of overall tsunami observations that might be useful in crisis situations, when time is too short to run propagation models. Thus, for each case, we show that the characteristic tsunami amplitude is a reasonable predictor of maximum runup in actual 3D geometry. We refer to the latter observation as the correspondence principle, which we propose to apply for rapid tsunami hazard assessment, in combination with the predictive tsunami amplitude equations. [ABSTRACT FROM AUTHOR]

Numerical simulations are performed with a two-dimensional (2D) fully nonlinear potential flow (FNPF) model for tsunami generation by two idealized types of submarine mass failure (SMF): underwater slides and slumps. These simulations feature rigid or deforming SMFs with a Gaussian cross section, translating down a plane slope. In each case, the SMF center of mass motion is expressed as a function of geometric, hydrodynamic, and material parameters, following a simple wavemaker formalism, and prescribed as a boundary condition in the FNPF model. Tsunami amplitudes and runup are obtained from computed free surface elevations. Model results are experimentally validated for a rigid 2D slide. Sensitivity studies are performed to estimate the effects of SMF–shape, type, and initial submergence depth—on the generated tsunamis. A strong SMF deformation during motion is shown to significantly enhance tsunami generation, particularly in the far-field. Typical slumps are shown to generate smaller tsunamis than corresponding slides. Both tsunami amplitude and runup are shown to depend strongly on initial SMF submergence depth. For the selected SMF idealized geometry, this dependence is simply expressed by power laws. Other sensitivity analyses are presented in a companion paper, and results from numerical simulations are converted into empirical curve fits predicting characteristic tsunami amplitudes as functions of nondimensional governing parameters. It should be stressed that these empirical formulas are only valid in the vicinity of the tsunami sources and, because of the complexity of the problem, many simplifications were necessary. It is further shown in the companion paper how 2D results can be modified to account for three-dimensional tsunami generation and used for quickly estimating tsunami hazard or for performing simple case studies. [ABSTRACT FROM AUTHOR]