Tsunami Arrival Time Research Articles

Source estimate and tsunami forecast from far‐field deep‐ocean tsunami waveforms—The 27 February 2010 Mw 8.8 Maule earthquake

AbstractWe inverted the 2010 Maule earthquake tsunami waveforms recorded at DART (Deep‐ocean Assessment and Reporting Tsunamis) stations in the Pacific Ocean by taking into account the effects of the seawater compressibility, elasticity of the solid Earth, and gravitational potential change. These effects slow down the tsunami speed and consequently move the slip offshore or updip direction, consistent with the slip distribution obtained by a joint inversion of DART, tide gauge, GPS, and coastal geodetic data. Separate inversions of only near‐field DART data and only far‐field DART data produce similar slip distributions. The former demonstrates that accurate tsunami arrival times and waveforms of trans‐Pacific tsunamis can be forecast in real time. The latter indicates that if the tsunami source area is as large as the 2010 Maule earthquake, the tsunami source can be accurately estimated from the far‐field deep‐ocean tsunami records without near‐field data.

The 16 September 2015 Chile Tsunami from the Post-Tsunami Survey and Numerical Modeling Perspectives

On September 16, 2015 a magnitude Mw 8.3 earthquake took place off the coast of the Coquimbo Region, Chile. Three tsunami survey teams covered approximately 700 km of the Pacific coast. The teams surveyed the area, recording 83 tsunami flow depth and runup measurements. The maximum runup was found to be 10.8 m at only one small bay, in front of the inferred tsunami source area. However, it was observed that runup in other locations rarely exceed 6 m. Tsunami runup was larger than those of the 2014 Pisagua event, despite the similar earthquake magnitude. Moreover, tsunami arrival times were found to be shorter than those of previous tsunamis along the Chilean subduction zone. Numerical simulations of the tsunami event showed a good agreement with field data, highlighting that tsunami arrival time and the spatial variation of the tsunami amplitudes were strongly influenced by the bathymetry, coastal morphology and the slip distribution of the causative earthquake.

Tsunami hazard assessment along the Chinese mainland coast from earthquakes in the Taiwan region

Tsunami disasters have been documented several times in Chinese history, mostly in the Taiwan region. To assess the tsunami hazard along the coast of mainland China from sources in Taiwan, this study analyzed historical tsunamis and undersea seismic events around Taiwan and found that the frequency and magnitude of earthquakes around Taiwan are significantly higher than in the adjacent Ryukyu and Manila trenches. The probabilistic seismic hazard analysis method was adopted to estimate the maximum possible earthquake magnitude around Taiwan. Then, six tsunami sources were assumed in those places where both earthquakes and tsunamis have occurred previously. Numerical models of the tsunamis were used to calculate the probable maximum tsunami amplitude and tsunami arrival time. The largest tsunami amplitude and the shortest arrival time were drawn on a GIS map. The modeling results provided a summary of tsunami hazards along the coast of mainland China from tsunami sources in Taiwan. The results showed that tsunamis triggered by the maximum possible earthquakes in the Taiwan region would arrive first at Zhejiang, Fujian, Guangdong, and Hainan Provinces within 3 h; the largest tsunami amplitude was up to 3.3 m. Thus, parts of Zhejiang, Fujian, and Guangdong Provinces were identified as regions with the highest hazard levels.

Beat-the-wave evacuation mapping for tsunami hazards in Seaside, Oregon, USA

Previous pedestrian evacuation modeling for tsunamis has not considered variable wave arrival times or critical junctures (e.g., bridges), and did not effectively communicate multiple evacuee travel speeds. We summarize an approach that identifies evacuation corridors, recognizes variable wave arrival times, and produces a map of minimum pedestrian travel speeds to reach safety, termed a “beat-the-wave” (BTW) evacuation analysis. We demonstrate the improved approach by evaluating difficulty of pedestrian evacuation of Seaside, Oregon, for a local tsunami generated by a Cascadia subduction zone earthquake. We establish evacuation paths by calculating the least-cost distance (LCD) to safety for every grid cell in a tsunami hazard zone using geospatial, anisotropic path distance algorithms. Minimum BTW speed to safety on LCD paths is calculated for every grid cell by dividing surface distance from that cell to safety by the tsunami arrival time at safety. We evaluated three scenarios of evacuation difficulty: (1) all bridges are intact with a 5-min evacuation delay from the start of earthquake, (2) only retrofitted bridges are considered intact with a 5-min delay, and (3) only retrofitted bridges are considered intact with a 10-min delay. BTW maps also take into account critical evacuation points along complex shorelines (e.g., peninsulas, bridges over shore-parallel estuaries) where evacuees could be caught by tsunami waves. The BTW map is able to communicate multiple pedestrian travel speeds, which are typically visualized by multiple maps with current LCD-based mapping practices. Results demonstrate that evacuation of Seaside is problematic seaward of the shore-parallel waterways for those with any limitations on mobility. Tsunami vertical evacuation refuges or additional pedestrian bridges may be effective ways of reducing loss of life seaward of these waterways.

Uncertainty in tsunami wave heights and arrival times caused by the rupture velocity in the strike direction of large earthquakes

In tsunami risk assessments, understanding the uncertainties involved in numerical simulations of tsunami wave heights and arrival times is important. However, few studies have been conducted to determine the effects of dynamic parameters (i.e., rupture velocity and rise time) in the simulation of tsunami wave heights and arrival times, although numerous studies have been conducted on the uncertainties that result from static parameters (i.e., top depth, strike, dip, rake, and fault slip). In this study, we calculated the variability in tsunami wave heights and their arrival times as a result of the uncertainties in the along-strike rupture velocity of faults. Specifically, numerical simulations of tsunamis were conducted with various rupture velocities and starting points within a large fault. The numerical analyses considered hypothetical bathymetry and dynamic effects and indicated that the uncertainties in the maximum wave height and its arrival time are greater as the water depth increases. The number of sub-faults affected the wave heights and suggested that we should consider these effects in numerical simulations of tsunamis. The results of the numerical analyses using the actual bathymetry of the Tohoku region in Japan showed that the spatial uncertainty in the maximum wave height at a 50 m depth had a 0.04 log-normal standard deviation based on a distribution of ratios between the calculated wave heights from numerical simulations with and without considering dynamic effects. The results of this study are practical for probabilistic tsunami hazard assessments for which we must evaluate the quantitative value of the spatial uncertainty in wave heights. This study is a basis for similar research in terms of offering a technique for evaluating wave height uncertainty due to the rupture velocity.

Building a Tsunami Simulation Database for the Tsunami Warning System in the Philippines

To enhance the tsunami warning operation system in the Philippines caused by earthquakes in and around the country, staff members of the Japan Meteorological Agency (JMA) joined the SATREPS program in 2012 to help building a tsunami simulation database in the Philippine Institute of Volcanology and Seismology (PHIVOLCS), which storesmultiple results of tsunami simulations such as estimated tsunami arrival times and heights at coasts for multiple hypothetical earthquakes of various hypocenter locations and magnitudes. The procedure to construct a database consists of several steps starting from setting assumed fault parameters and others, proceeding to tsunami simulations and data creation to be stored in the database, and as the last step, creating a searching system which picks results from the database according to the location and magnitude of an earthquake. As of July 2014, the PHIVOLCS has stored the results of tsunami simulations conducted for more than 30,000 assumed faults for local tsunamis. The searching system is also prepared which enables to get a quick grasp of expected tsunami features quantitatively. With this database and the searching system, the PHIVOLCS is in near future to issue initial tsunami warnings based on the information of estimated tsunami arrival times and heights immediately after the hypocenter location and magnitude of an earthquake are determined. When the necessary coordination with related organizations as well as the public education for the system and warning messages are ready, the PHIVOLCS will start the enhanced local tsunami warning operation.

Tsunami modeling from the seismic CMT solution considering the dispersive effect: a case of the 2013 Santa Cruz Islands tsunami

The development of real-time tsunami forecast and rapid tsunami warning systems is crucial in order to mitigate tsunami disasters. The present study shows that tsunami prediction from a seismic centroid moment tensor (CMT) solution would work satisfactorily for the 2013 Santa Cruz Islands earthquake (Mw 8.0) tsunami even though the earthquake source had been modeled as a complicated source characterized by two patches of slip in a past study. We numerically solved the equations for a linear dispersive wave on a spherical coordinate system from the initial tsunami height distribution derived from the CMT solution and a classical scaling law for earthquake faults. The tsunami simulations well explain the observed tsunami arrival times, polarities of initial wave, and maximum amplitudes obtained by deep-ocean pressure measurements. The comparison of the simulation results from dispersive and non-dispersive modeling indicates that the dispersive modeling reproduced the observed waveforms better than the conventional non-dispersive approach. Also, the area affected by a maximum height greater than 0.4 m is decreased by approximately 34% by using dispersion modeling. Those results indicate that the tsunami prediction based on CMT solutions is useful for early warning, and the modeling of dispersion can significantly improve performance.

A methodology for near‐field tsunami inundation forecasting: Application to the 2011 Tohoku tsunami

AbstractExisting tsunami early warning systems in the world can give either one or a combination of estimated tsunami arrival times, heights, or qualitative tsunami forecasts before the tsunami hits near‐field coastlines. A future tsunami early warning system should be able to provide a reliable near‐field tsunami inundation forecast on high‐resolution topography within a short time period. Here we describe a new methodology for near‐field tsunami inundation forecasting. In this method, a precomputed tsunami inundation and precomputed tsunami waveform database is required. After information about a tsunami source is estimated, tsunami waveforms at nearshore points can be simulated in real time. A scenario that gives the most similar tsunami waveforms is selected as the site‐specific best scenario and the tsunami inundation from that scenario is selected as the tsunami inundation forecast. To test the algorithm, tsunami inundation along the Sanriku Coast is forecasted by using source models for the 2011 Tohoku earthquake estimated from GPS, W phase, or offshore tsunami waveform data. The forecasting algorithm is capable of providing a tsunami inundation forecast that is similar to that obtained by numerical forward modeling but with remarkably smaller CPU time. The time required to forecast tsunami inundation in coastal sites from the Sendai Plain to Miyako City is approximately 3 min after information about the tsunami source is obtained. We found that the tsunami inundation forecasts from the 5 min GPS, 5 min W phase, 10 min W phase fault models, and 35 min tsunami source model are all reliable for tsunami early warning purposes and quantitatively match the observations well, although the latter model gives tsunami forecasts with highest overall accuracy. The required times to obtain tsunami forecast from the above four models are 8 min, 9 min, 14 min, and 39 min after the earthquake, respectively, or in other words 3 min after receiving the source model. This method can be useful in developing future tsunami forecasting systems with a capability of providing tsunami inundation forecasts for locations near the tsunami source area.

Tsunami Resonance in Palma Bay and Harbor, Majorca Island, as Induced by the 2003 Western Mediterranean Earthquake

AbstractThe tsunami induced by the May 21, 2003, Algerian Boumerdes-Zemmouri earthquake (moment magnitude Mw = 6.9) propagated across the western Mediterranean Basin, thereby causing material damages in some harbors and coastal areas. This was the case in the Balearic Islands and particularly the Palma harbor. Attempts to simulate the 2003 tsunami event found discrepancies between tsunami arrival times and wave amplitude when comparing tide gauge records with results from numerical models. To date, all published model results of the amplitude of the tsunami are underestimations, attributed to numerical limitations due to the lack of high-resolution bathymetry and poor definition of harbor geometry. Other views suggest the inappropriateness of the available seismic source parameterizations and the possible occurrence of submarine landsliding triggered by the earthquake that has not been included in the numerical simulations. In this article we present the results of a numerical study aimed at better unders...

Effects of coastal submarine canyons on tsunami propagation and impact

Abstract We analyse the variations produced on tsunami propagation and impact over a straight coastline because of the presence of a submarine canyon incised in the continental margin. For ease of calculation we assume that the shoreline and the shelf edge are parallel and that the incident wave approaches them normally. A total of 512 synthetic scenarios have been computed by combining the bathymetry of a continental margin incised by a parameterised single canyon and the incident tsunami waves. The margin bathymetry, the canyon and the tsunami waves have been generated using mathematical functions (e.g. Gaussian). Canyon parameters analysed are: (i) incision length into the continental shelf, which for a constant shelf width relates directly to the distance from the canyon head to the coast, (ii) canyon width, and (iii) canyon orientation with respect to the shoreline. Tsunami wave parameters considered are period and sign. The COMCOT tsunami model from Cornell University was applied to propagate the waves across the synthetic bathymetric surfaces. Five simulations of tsunami propagation over a non-canyoned margin were also performed for reference. The analysis of the results reveals a strong variation of tsunami arrival times and amplitudes reaching the coastline when a tsunami wave travels over a submarine canyon, with changing maximum height location and alongshore extension. In general, the presence of a submarine canyon lowers the arrival time to the shoreline but prevents wave build-up just over the canyon axis. This leads to a decrease in tsunami amplitude at the coastal stretch located just shoreward of the canyon head, which results in a lower run-up in comparison with a non-canyoned margin. Contrarily, an increased wave build-up occurs on both sides of the canyon head, generating two coastal stretches with an enhanced run-up. These aggravated or reduced tsunami effects are modified with (i) proximity of the canyon tip to the coast, amplifying the wave height, (ii) canyon width, enlarging the areas with lower and higher maximum height wave along the coastline, and (iii) canyon obliquity with respect to the shoreline and shelf edge, increasing wave height shoreward of the leeward flank of the canyon. Moreover, the presence of a submarine canyon near the coast produces a variation of wave energy along the shore, eventually resulting in edge waves shoreward of the canyon head. Edge waves subsequently spread out alongshore reaching significant amplitudes especially when coupling with tsunami secondary waves occurs. Model results have been groundtruthed using the actual bathymetry of Blanes Canyon area in the North Catalan margin. This paper underlines the effects of the presence, morphology and orientation of submarine canyons as a determining factor on tsunami propagation and impact, which could prevail over other effects deriving from coastal configuration.

Effects of the Tsunami Countermeasures Focusing on the Tsunami Arrival Time in Kamakura

Effects of the Tsunami Countermeasures Focusing on the Tsunami Arrival Time in Kamakura

토카이, 토난카이 및 난카이 대규모 지진으로 인한 지진해일의 전파특성에 관한 수치적 연구

After the 2011 Tohoku Earthquake, it has been pointed out that Tokai, Tonankai and Nankai massive earthquakes with a magnitude of 9.0 could strike the Pacific coasts in western Japan. This study aims at investigating numerically propagation characteristics of tsunami generated by a 9.0 magnitude Tokai, Tonankai and Nankai massive earthquakes on the Pacific coasts and three major bays in Japan, Tokyo Bay, Ise Bay and Osaka Bay. It was revealed from the numerical results that the tsunami heights on the Pacific coasts for M9.0 earthquake were about twice as much as those for M8.7 earthquake and the first tsunami arrival time was faster at some areas distant from the tsunami source. Moreover, high water level in the bays was recognized to continue for a long time because of the enclosed bays.

Tsunamis from the Arica-Tocopilla source region and their effects on ports of Central Chile

The last great earthquake in northern Chile took place in 1877, and the ensuing tsunami affected not only that region but also Central Chile. For example, the Bay of Concepcion, which is located 1,500 km south of the tsunami source, experienced an inundation height of around 3 m. Ports are important in the Chilean economy, due to the fact that a large percentage of Chilean exports (excluding copper) use ports located in Central Chile. With this in mind, the authors investigated the potential effect of an 1877-like tsunami on the main ports of Central Chile. To do this, the dispersive wave model Non-hydrostatic Evolution of Ocean WAVEs was used. In addition, the first tsunami forecast model for Talcahuano, inside the Bay of Concepcion, was developed by means of numerical simulation of several events of different moment magnitudes. The results showed that most of the important ports (Valparaiso, San Antonio, San Vicente and Coronel) had inundation heights on the order of just 1 m, while inundation levels in Talcahuano reached up to 3.5 m. The forecast model for Talcahuano uses only earthquake magnitude, focal depth and tide level to determine tsunami inundation heights. In addition, the tsunami arrival time was computed to be 3 h, and the maximum tsunami amplitude takes place at 4 h and 45 min after the earthquake.

Tsunami Mapping Related to Local Earthquakes on the French–Italian Riviera (Western Mediterranean)

The Ligurian coast, located at the French–Italian border, is densely populated as well as a touristic area. It is also a location where earthquakes and underwater landslides are recurrent. The nature of the local tsunamigenesis is therefore a legitimate question, because no tsunami warning system can resolve tsunami arrival times of a few minutes, which is the case for the area. As far as the seismicity of the area is concerned, the frequent recurrent earthquakes are generally of moderate magnitude: most of them are lower than Mw 5. However, the relatively large Mw 6.9 earthquake (Larroque et al., in Geophys J Int, 2012. doi:10.1111/j.1365-246X.2012.05498.x) that occurred on the February 23, 1887, offshore of Imperia (Italian Riviera) is quite emblematic. This unusual event for the region merits a complete study: the quantification of its rupture mechanism is essential (1) to understand the regional active deformation, but also (2) to evaluate its tsunamigenesis potential by deriving relevant rupture scenarios obtained from our knowledge of the event; for that purpose the event is extensively described here. The first point has been the subject of quite a few studies based on the seismotectonics of the area. The last documented approach has been completed by Larroque et al. (Geophys J Int, 2012. doi:10.1111/j.1365-246X.2012.05498.x) who proposed a rupture scenario involving a reverse faulting along a north dipping fault and favoring a Mw 6.9 magnitude. In the present paper (1) we study the accuracy of their solutions in relation to the computational grid spacing and the dispersive/nondispersive parameterization, (2) based on an uncertainty on the recorded wave amplitude of the Genoa tide gauge they used, we propose a Mw 6.7 earthquake magnitude solution for the event (the kinematics is unchanged), co-existing with the Mw 6.9, (3) we evaluate the tsunami coastal impact of the 1887 event, and (4) we test a range of possible ruptures that local faults may undergo in order to propose a synoptic mapping of the tsunami threat in the area. The spatial distribution of the maximum wave height (MWH) is provided with a tentative identification of the processes that are responsible for it. This latter issue is imperative in order to make our mapping as generic as possible in the framework of our deterministic approach (based on realistic scenarios and not on ensemble statistics). The predictions suggest that the wave impact is mostly local, considering the relatively moderate size of the rupture planes. Although the present-day seismicity in this region is moderate, stronger earthquakes (M > 6.5) have occurred in the past. The studied scenarios show that for such events specific localities along the French–Italian Riviera may experience very significant MWH related to the shallow focal depth tested for such scenarios. We may reasonably conclude that the tsunami threat is relatively significant and uniform at the Italian side of the Riviera (from Ventimiglia to Imperia), while it is more localized (sporadic) at the French side from Antibes to Menton with, however, higher local level of inundation, e.g., Nice city center.

Estimating the effect of Earth elasticity and variable water density on tsunami speeds

The speed of tsunami waves is typically calculated using the shallow‐water approximation over a rigid‐body Earth. Recent comparisons of tsunami arrival times from the 11 March 2011 tsunami suggest, however, that the standard formulation has errors around the 1% level, and it has been suggested that the elasticity of the Earth can explain the discrepancy. While previous work has indeed shown that such elastic deformation can modify tsunami speeds, the effect has been neglected partly due to the difficulty in understanding how large this elastic effect is. Here, we remedy this by providing a new derivation and expression for how to incorporate the first‐order effect that solid Earth elasticity and ocean water compressibility have on tsunami speeds. This result is shown to agree approximately with previous theory and helps to explain observed timing discrepancies from the 11 March 2011 tsunami. The dispersive elastic correction and the non‐dispersive compressibility correction together may account for the majority of the observed discrepancy.

Estimación de la amenaza por tsunami en el municipio de San Andrés de Tumaco, Pacífico colombiano, utilizando información LiDAR

Se estimó la amenaza por tsunami en el área urbana del municipio de San Andrés de Tumaco, a partir de la simulación numérica de escenarios basados en el evento real de tsunami de 1979 que causó daños considerables en el municipio. Se utilizó batimetría de detalle de 15 m de resolución espacial (multihaz) e información Light Detection and Ranging (LiDAR) que permite representar la altimetría del terreno del área de estudio con una exactitud posicional de ±30 cm en el plano vertical y ±30 cm en el plano horizontal de acuerdo con los datos adquiridos por Dimar. Los resultados indican que el escenario denominado E1, simulado con parámetros macrosísmicos y de marea idénticos a los del escenario utilizado para elaborar el mapa oficial del municipio en 2004, provoca cambios significativos en las zonas de inundación del área urbana del municipio. El tiempo de llegada del tsunami varía en promedio entre 20 y 18 minutos. Finalmente, se realiza una comparación entre los mapas de inundación por tsunami elaborados para el municipio en 2004 y 2012, encontrando que la isla de Tumaco, con inundación aproximada del 88 % en el mapa 2004, presenta inundación del 96 % en el mapa de 2012, lo cual representa más de 100 000 m² de área inundada en la isla. La determinación de escenarios de inundación por tsunami contribuye a la disminución de la vulnerabilidad de los pobladores de las zonas costeras ante este evento de origen natural, toda vez que son una herramienta base para la formulación de planes municipales de contingencia ante tsunami y permiten a la Unidad Nacional de Gestión del Riesgo la toma de decisiones concernientes al manejo de desastres, a los planes de capacitación en respuesta ante tsunami y a la formulación de estrategias de mitigación.

Finite Element Analysis of Tsunami by Viscous Shallow-Water Equations

In this paper, viscous shallow-water equations are derived from three-dimensional Navier-Stokes equations under the hydrostatic assumption. The viscous shallow-water equations are approximated by the finite element method based on our numerical scheme developed in 1978. This approach is used to simulate a tsunami in Hakata Bay. Results show a reasonable estimate of the tsunami arrival time.

Effects of the Tohoku tsunami of March 11, 2011 on the Pacific coast of Russia

The records of the Tohoku tsunami of March 11, 2011, obtained at the nearest Deep-Ocean Assessment and Reporting of Tsunamis (DART) stations and the coastal telemetric recorders of the Russian Tsunami Warning System, are analyzed. Such parameters as tsunami arrival times, heights of the first and maximal waves, and predominant periods are presented. The eyewitness accounts and photographs of tsunami effects are presented. The tsunami height distribution along the coast of Kuril Islands is discussed.

Tsunami Characteristics along The Coast of Biak Island based on the 1996 Biak Tsunami Traces

Identification on tsunami traces had been conducted along the coast of Biak Island, Papua, to recognize the character of tsunami potential in this region, referring to the 1996 tsunami event. This study is to observe the influence of tsunami to the environment and tsunami character itself which can be learned from tsunami deposit. According to the 1996 Biak tsunami run up distributions, it can be observed that the maximum tsunami run up was found at the coast which has an undulating to steep morphology rather than other places which has a relatively flat one. The 1996 Biak Tsunami arrival times were approximately between 10 and 15 minutes, such as at the northern and southern coasts of Biak, except for the western one which is about 1 to 5 minutes. This was influenced by the local bathymetry and another possible source triggering tsunami such as a local submarine landslide. The number of tsunami waves were between 2 and 4, and the second one was usually the highest. Based on a sedimentological analysis, the 1996 tsunami deposit is characterized by the dominant coarse sand, while grain size distribution curve shows a character of transportation process similar to an ordinary beach process dominated by saltation current. The foraminifera fossil content tends to indicate that the tsunami deposit was derived from > 200 m seafloor depth (bathyal zone).

Tsunami Characteristics along The Coast of Biak Island based on the 1996 Biak Tsunami Traces

DOI: 10.17014/ijog.v7i1.135Identification on tsunami traces had been conducted along the coast of Biak Island, Papua, to recognize the character of tsunami potential in this region, referring to the 1996 tsunami event. This study is to observe the influence of tsunami to the environment and tsunami character itself which can be learned from tsunami deposit. According to the 1996 Biak tsunami run up distributions, it can be observed that the maximum tsunami run up was found at the coast which has an undulating to steep morphology rather than other places which has a relatively flat one. The 1996 Biak Tsunami arrival times were approximately between 10 and 15 minutes, such as at the northern and southern coasts of Biak, except for the western one which is about 1 to 5 minutes. This was influenced by the local bathymetry and another possible source triggering tsunami such as a local submarine landslide. The number of tsunami waves were between 2 and 4, and the second one was usually the highest. Based on a sedimentological analysis, the 1996 tsunami deposit is characterized by the dominant coarse sand, while grain size distribution curve shows a character of transportation process similar to an ordinary beach process dominated by saltation current. The foraminifera fossil content tends to indicate that the tsunami deposit was derived from > 200 m seafloor depth (bathyal zone).