A multi-scenario assessment of the seismogenic tsunami hazard for Bangladesh

2019 ◽  
Vol 11 (2) ◽  
pp. 156-168
Author(s):  
Janaka J. Wijetunge
Keyword(s):  
Subduction Zones ◽  
Submarine Canyon ◽  
Tsunami Hazard ◽  
Seismic Zone ◽  
Tsunami Propagation ◽  
Content Type ◽  
Arrival Times ◽  
Tsunami Waves ◽  
Scenario Assessment ◽  
Seismic Scenarios

Purpose This paper aims to describe a multi-scenario assessment of the seismogenic tsunami hazard for Bangladesh from active subduction zones in the Indian Ocean region. Two segments of the Sunda arc, namely, Andaman and Arakan, appear to pose a tsunamigenic seismic threat to Bangladesh. Design/methodology/approach High-resolution numerical simulations of tsunami propagation toward the coast of Bangladesh have been carried out for eight plausible seismic scenarios in Andaman and Arakan subduction zones. The numerical results have been analyzed to obtain the spatial variation of the maximum tsunami amplitudes as well as tsunami arrival times for the entire coastline of Bangladesh. Findings The results suggest that the tsunami heights are amplified on either side of the axis of the submarine canyon which approaches the nearshore sea off Barisal in the seaboard off Sundarban–Barisal–Sandwip. Moreover, the computed tsunami amplitudes are comparatively higher north of the latitude 21.5o in the Teknaf–Chittagong coastline. The calculated arrival times indicate that the tsunami waves reach the western half of the Sundarban–Barisal–Sandwip coastline sooner, while shallow water off the eastern half results in a longer arrival time for that part of the coastline, in the event of an earthquake in the Andaman seismic zone. On the other hand, most parts of the Chittagong–Teknaf coastline would receive tsunami waves almost immediately after an earthquake in the northern segment of the Arakan seismic zone. Originality/value The present assessment includes probabilistic measures of the tsunami hazard by incorporating several probable seismic scenarios corresponding to recurrence intervals ranging from 25 years to over 1,000 years.

Assessment of potential tsunamigenic seismic hazard to Sri Lanka

2010 ◽  
Vol 1 (2) ◽  
pp. 207-220 ◽  
Author(s):  
Janaka Wijetunge
Keyword(s):  
Sri Lanka ◽  
Indian Ocean ◽  
Seismic Hazard ◽  
Subduction Zones ◽  
Volcanic Eruptions ◽  
Tsunami Hazard ◽  
Worst Case ◽  
Content Type ◽  
Seismic Zones ◽  
The Indian Ocean

PurposeThe purpose of this paper is to present an assessment of the potential tsunamigenic seismic hazard to Sri Lanka from all active subduction zones in the Indian Ocean Basin.Design/methodology/approachThe assessment was based on previous studies as well as past seismicity of the subducion zones concerned.FindingsAccordingly, four seismic zones capable of generating teletsunamis that could reach Sri Lanka have been identified, namely, Northern Andaman‐Myanmar, Northern Sumatra‐Andaman and Southern Sumatra in the Sunda trench and Makran in the Northern Arabian Sea. Moreover, plausible worst‐case earthquake scenarios and respective fault parameters for each of these seismic zones have been recommended.Research limitations/implicationsHowever, other potential tsunami sources such as seismic activity in the near‐field, submarine landslides and volcanic eruptions have not been considered.Practical implicationsNumerical simulations of tsunami propagation have been carried out for each of the four scenarios in order to assess the potential impact along the coastline of Sri Lanka. Such information relating to the spatial distribution of the likely tsunami amplitudes and arrival times for Sri Lanka would help authorities responsible for evacuation to make a better judgment as to the level of threat in different areas along the coastline, and act accordingly, if a large earthquake were to occur in any of the subduction zones in the Indian Ocean.Originality/valueIn the absence of comprehensive probabilistic assessments of the tsunami hazard to Sri Lanka, this paper's recommendations would provide the necessary framework for the development of deterministic tsunami hazard maps for the shoreline of Sri Lanka.

scholarly journals TSUNAMI HAZARD AND DESIGN OF COASTAL STRUCTURES

1976 ◽  
Vol 1 (15) ◽  
pp. 130
Author(s):  
George Pararas-Carayannis
Keyword(s):  
Tsunami Wave ◽  
Time History ◽  
Tsunami Hazard ◽  
Wave System ◽  
Tsunami Generation ◽  
Coastal Structures ◽  
Tsunami Height ◽  
Tsunami Propagation ◽  
Coastal Site ◽  
Tsunami Waves

Damage of coastal structures by tsunamis results by the direct and indirect action of hydrostatic and dynamic pressures, foundation failures, overtopping and flooding. Reliable assessment of the potential tsunami hazard at a coastal site and adequate engineering design of critical structures require analysis and understanding of all aspects of a tsunami system leading to its terminal behavior. Description of the space-time history of tsunami waves generated by impulsive disturbances require consideration of events and processes in the following regimes: (a) generation; (b) propagation and dispersion; and (c) termination. Processes and events in each regime during the development of a tsunami are under their own unique hydrodynamic constraints but are dependent on what has preceeded. In predicting tsunami wave characteristics at some distance from the generating source, the error structure may be pyramidal. Essential to any method of tsunami prediction at a distant or a nearby coast will be the full consideration and study of tsunami generative mechanisms. If the tsunami generation mechanics cannot be deduced with a reasonable degree of accuracy, it is not likely that the tsunami terminal aspects will be reliably predicted. Prediction of tsunami height at a distant or at a nearby coast requires knowledge of the magnitude and type of ground displacements in the tsunami generating area and of the characteristics of the surface waves resulting from such action. Although all mechanisms involved during tsunami generation are not fully understood, it is possible to obtain a suitable tsunami initiating function through the use of experimental data, historical data, and established empirical relationships, for each type of generating mechanism. Reliable computation of the tsunami propagation effects over and across the ocean can be obtained with proper modeling to provide an adequate description of the tsunami energy flow through the use of physical and numerical studies. Similarly, the terminal aspects and nearshore modification of the tsunami wave system can be approximated to provide the engineering criteria necessary for the assessment of the potential tsunami hazard at a coastal site.

scholarly journals Tsunami hazard assessment in the Ionian Sea due to potential tsunamogenic sources – results from numerical simulations

2010 ◽  
Vol 10 (5) ◽  
pp. 1021-1030 ◽  
Author(s):  
G-A. Tselentis ◽  
G. Stavrakakis ◽  
E. Sokos ◽  
F. Gkika ◽  
A. Serpetsidaki
Keyword(s):  
Great Majority ◽  
Tsunami Hazard ◽  
Fault System ◽  
Coseismic Deformation ◽  
Seismic Sources ◽  
Ionian Sea ◽  
Tsunami Propagation ◽  
Arrival Times ◽  
System A ◽  
First Time

Abstract. In spite of the fact that the great majority of seismic tsunami is generated in ocean domains, smaller basins like the Ionian Sea sometimes experience this phenomenon. In this investigation, we study the tsunami hazard associated with the Ionian Sea fault system. A scenario-based method is used to provide an estimation of the tsunami hazard in this region for the first time. Realistic faulting parameters related to four probable seismic sources, with tsunami potential, are used to model expected coseismic deformation, which is translated directly to the water surface and used as an initial condition for the tsunami propagation. We calculate tsunami propagation snapshots and mareograms for the four seismic sources in order to estimate the expected values of tsunami maximum amplitudes and arrival times at eleven tourist resorts along the Ionian shorelines. The results indicate that, from the four examined sources, only one possesses a seismic threat causing wave amplitudes up to 4 m at some tourist resorts along the Ionian shoreline.

Seismically Derived Ground Tilts Related to the 2010 Chilean Tsunami

2021 ◽  
Author(s):  
Jui-Chun Freya Chen ◽  
Wu-Cheng Chi ◽  
Chu-Fang Yang
Keyword(s):  
Deep Ocean ◽  
Propagation Model ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Tsunami Propagation ◽  
Ground Tilt ◽  
Tsunami Waves ◽  
The Pacific ◽  
Seismic Networks ◽  
Back Azimuth

Abstract Developing new ways to observe tsunami contributes to tsunami research. Tidal and deep-ocean gauges are typically used for coastal and offshore observations. Recently, tsunami-induced ground tilts offer a new possibility. The ground tilt signal accompanied by 2010 Mw 8.8 Chilean earthquake were observed at a tiltmeter network in Japan. However, tiltmeter stations are usually not as widely installed as broadband seismometers in other countries. Here, we studied broadband seismic records from Japan’s F-net and found ground tilt signals consistent with previously published tiltmeter dataset for this particular tsunamic event. Similar waveforms can also be found in broadband seismic networks in other countries, such as Taiwan, as well as an ocean-bottom seismometer. We documented a consistent time sequence of evolving back-azimuth directions of the tsunami waves at different stages of tsunami propagation through beamforming-frequency–wavenumber analysis and particle-motion analysis; the outcomes are consistent with the tsunami propagation model provided by the Pacific Tsunami Warning Center. These results shown that dense broadband seismic networks can provide a useful complementary dataset, in addition to tiltmeter arrays and other networks, to study or even monitor tsunami propagation using arrayed methods.

scholarly journals TSUNAMI PHASE SPEED REDUCTION DUE TO WATER COMPRESSIBILTY

2018 ◽  
pp. 9
Author(s):  
Ali Abdolali ◽  
James T. Kirby
Keyword(s):  
Arrival Time ◽  
Phase Speed ◽  
Propagation Speed ◽  
Frequency Dispersion ◽  
Wave Theory ◽  
Polar Coordinates ◽  
Ocean Bottom ◽  
Tsunami Propagation ◽  
Boussinesq Model ◽  
Tsunami Waves

Most existing tsunami propagation models consider the ocean to be an incompressible, homogenous medium. Recently, it has been shown that a number of physical features can slow the propagation speed of tsunami waves, including wave frequency dispersion, ocean bottom elasticity, water compressibility and thermal or salinity stratification. These physical effects are secondary to the leading order, shallow water or long wave behavior, but still play a quantifiable role in tsunami arrival time, especially at far distant locations. In this work, we have performed analytical and numerical investigations and have shown that consideration of those effects can actually improve the prediction of arrival time at distant stations, compared to incompressible forms of wave equations. We derive a modified Mild Slope Equation for Weakly Compressible fluid following the method proposed by Sammarco et al. (2013) and Abdolali et al. (2015) using linearized wave theory, and then describe comparable extensions to the Boussinesq model of Kirby et al. (2013). Both models account for water compressibility and compression of static water column to simulate tsunami waves. The mild slope model is formulated in plane Cartesian coordinates and is thus limited to medium propagation distances, while the Boussinesq model is formulated in spherical polar coordinates and is suitable for ocean scale simulations.

3D linked megathrust, dynamic rupture and  tsunami propagation and inundation modeling:  Dynamic effects of supershear and tsunami earthquakes 

2021 ◽  
Author(s):  
Sara Aniko Wirp ◽  
Alice-Agnes Gabriel ◽  
Elizabeth H. Madden ◽  
Maximilian Schmeller ◽  
Iris van Zelst ◽  
...  
Keyword(s):  
Subduction Zones ◽  
Large Scale ◽  
Dynamic Models ◽  
Initial Conditions ◽  
Poisson Ratio ◽  
Fault Slip ◽  
Moment Magnitude ◽  
Dynamic Rupture ◽  
S Wave ◽  
Tsunami Propagation

<p>Earthquake rupture dynamic models capture the variability of slip in space and time while accounting for the structural complexity which is characteristic for subduction zones. The use of a geodynamic subduction and seismic cycling (SC) model to initialize dynamic rupture (DR) ensures that initial conditions are self-consistent and reflect long-term behavior. We extend the 2D geodynamical subduction and SC model of van Zelst et al. (2019) and use it as input for realistic 3-dimensional DR megathrust earthquake models. We follow the subduction to tsunami run-up linking approach described in Madden et al. (2020), including a complex subduction setup along with their resulting tsunamis. The distinct variation of shear traction and friction coefficients with depth lead to realistic average rupture speeds and dynamic stress drop as well as efficient tsunami generation. </p><p>We here analyze a total of 14 subduction-initialized 3D dynamic rupture-tsunami scenarios. By varying the hypocentral location along arc and depth, we generate 12 distinct unilateral and bilateral earthquakes with depth-variable slip distribution and directivity, bimaterial, and geometrical effects in the dynamic slip evolutions. While depth variations of the hypocenters barely influence the tsunami behavior, lateral varying nucleation locations lead to a shift in the on-fault slip which causes time delays of the wave arrival at the coast. The fault geometry of our DR model that arises during the SC model is non-planar and includes large-scale roughness. These features (topographic highs) trigger supershear rupture propagation in up-dip or down-dip direction, depending on the hypocentral depth.</p><p>In two additional scenarios, we analyze variations in the energy budget of the DR scenarios. In the SC model, an incompressible medium is assumed (ν=0.5) which is valid only for small changes in pressure and temperature. Unlike in the DR model where the material is compressible and a different Poisson’s ratio (ν=0.25) has to be assigned. Poisson’s ratios between 0.1 and 0.4 stand for various compressible materials. To achieve a lower shear strength of all material on and off the megathrust fault and to facilitate slip, we increase the Poisson ratio in the DR model to ν=0.3 which is consistent with basaltic rocks. As a result, larger fault slip is concentrated at shallower depths and generates higher vertical seafloor displacement and earthquake moment magnitude respectively. Even though the tsunami amplitudes are much higher, the same dynamic behavior as in the twelve hypocenter-variable models can be observed. Lastly, we increase fracture energy by changing the critical slip distance in the linear slip-weakening frictional parameterization. This generates a tsunami earthquake (Kanamori, 1972) characterized by low rupture velocity (on average half the amount of s-wave speed) and low peak slip rate, but at the same time large shallow fault slip and moment magnitude. The shallow fault slip of this event causes the highest vertical seafloor uplift compared to all other simulations. This leads to the highest tsunami amplitude and inundation area while the wavefront hits the coast delayed compared to the other scenarios.</p>

Tsunami Hazard of the Caspian Sea

2021 ◽  
Author(s):  
Alisa Medvedeva ◽  
Igor Medvedev
Keyword(s):  
Sea Level ◽  
Caspian Sea ◽  
Tsunami Hazard ◽  
Seismic Sources ◽  
Deterministic Approach ◽  
The Caspian Sea ◽  
Tsunami Waves ◽  
The Mean ◽  
Run Up ◽  
Sea Coast

<p>A regional model of tsunami seismic sources in the zone of the Main Caucasian thrust has been developed. The parameters of probable models of seismic sources and their uncertainties were estimated based on the available data on historical earthquakes and active faults of the region. The scenario modeling technique was used for the tsunami zoning of the Caspian Sea coast. The time period covered by the model catalog of earthquakes used to calculate the generation and propagation of tsunamis is about 20 000 years, which is longer than the recurrence periods of the strongest possible earthquakes. The recurrence graphs of the calculated maximum tsunami heights for the entire sea coast were plotted. On their basis, the maximum heights of tsunami waves on the coast were calculated with recurrence periods of 250, 500, 1000 and 5000 years and the corresponding survey maps of the tsunami zoning of the Caspian Sea were created. The algorithm for calculating the tsunami run-up on the coast is improved, taking into account the residual (postseismic) displacements of the bottom and land relief. Estimates of tsunami hazard for the coast near the city of Kaspiysk were carried out: within the framework of the deterministic approach, the maximum wave heights and run-up distance were calculated. It is shown that the deterministic approach slightly overestimates the maximum heights of tsunami waves with certain return periods. It is shown that changes in the mean sea level can affect the features of the propagation of tsunami waves in the Caspian Sea. Thus, at an average sea level of -25-26 m, the Kara-Bogaz-Gol Bay is linked with the entire sea through a narrow strait. It leads to the propagation of tsunami waves into the water area of the bay and a decrease in wave height on the eastern coast of the sea. When the mean sea level decreases below -27 m, the positive depths in the strait disappear and water exchange through the strait stops, and the wave height in this part of the sea increases.</p>

scholarly journals Dispersive mudslide-induced tsunamis

1998 ◽  
Vol 5 (3) ◽  
pp. 127-136 ◽  
Author(s):  
A. Rubino ◽  
S. Pierini ◽  
J. O. Backhaus
Keyword(s):  
Solitary Waves ◽  
Intermediate Phase ◽  
Water Model ◽  
Tsunami Propagation ◽  
Tsunami Waves ◽  
Open Sea ◽  
Petviashvili Equation ◽  
Wave Forms ◽  
Generation Region ◽  
Run Up

Abstract. A nonlinear nested model for mudslide-induced tsunamis is proposed in which three phases of the life of the wave, i.e. the generation, far-field propagation and costal run-up are described by means of different mathematical models, that are coupled through appropriate matching procedures. The generation and run-up dynamics are simulated through a nonlinear shallow-water model with movable lateral boundaries: in the generation region two active layers are present, the lower one describing the slide descending on a sloping topography. For the intermediate phase, representing wave propagation far from the generation region, the hydrostatic assumption is not assumed as appropriate in general and, therefore, a nonlinear model allowing for weak phase dispersion, namely a Kadomtsev-Petviashvili equation, is used. This choice is made in order to assess the relevance of dispersive features such as solitary waves and dispersive tails. It is shown that in some realistic circumstances dispersive mudslide-induced tsunami waves can be produced over relatively short, distances. In such cases the use of a hydrostatic model throughout the whole tsunami history turns out to give erroneous results. In particular, when solitary waves are generated during the tsunami propagation in the open sea, the resulting run-up process yields peculiar wave forms leading to amplified coastal inundations with respect to a mere hydrostatic context.

scholarly journals Post-event field survey of 28 September 2018 Sulawesi earthquake and tsunami

2019 ◽  
Vol 19 (12) ◽  
pp. 2781-2794 ◽  
Author(s):  
Wahyu Widiyanto ◽  
Purwanto B. Santoso ◽  
Shih-Chun Hsiao ◽  
Rudy T. Imananta
Keyword(s):  
Field Survey ◽  
Severe Damage ◽  
Arrival Times ◽  
Tsunami Waves ◽  
Tsunami Measurements ◽  
Survey Results ◽  
Earthquake Event ◽  
Run Up ◽  
2018 Sulawesi Earthquake ◽  
Made In

Abstract. An earthquake with a magnitude of Mw=7.5 that occurred in Sulawesi, Indonesia, on 28 September 2018 triggered liquefaction and tsunamis that caused severe damage and many casualties. This paper reports the results of a post-tsunami field survey conducted by a team with members from Indonesia and Taiwan that began 13 d after the earthquake. The main purpose of this survey was to measure the run-up of tsunami waves and inundation and observe the damage caused by the tsunami. Measurements were made in 18 selected sites, most in Palu Bay. The survey results show that the run-up height and inundation distance reached 10.7 m in Tondo and 488 m in Layana. Inundation depths of 2 to 4 m were common at most sites and the highest was 8.4 m in Taipa. The arrival times of the tsunami waves were quite short and different for each site, typically about 3–8 min from the time of the main earthquake event. This study also describes the damage to buildings and infrastructure and coastal landslides.

A scenario-based assessment of the tsunami hazard in Palermo, northern Sicily, and the southern Tyrrhenian Sea

2020 ◽  
Vol 500 (1) ◽  
pp. 63-80 ◽  
Author(s):  
Jack Dignan ◽  
Aaron Micallef ◽  
Christof Mueller ◽  
Attilio Sulli ◽  
Elisabetta Zizzo ◽  
...  
Keyword(s):  
Wave Height ◽  
Near Field ◽  
Mass Movement ◽  
Tsunami Hazard ◽  
Small Scale ◽  
Maximum Height ◽  
Northern Coast ◽  
Tyrrhenian Sea ◽  
Worst Case ◽  
Tsunami Waves

AbstractPalermo is a populous city situated on the northern coast of Sicily, bordered by the Tyrrhenian Sea. This central part of the Mediterranean Sea features dramatic bathymetry, numerous subaqueous landslides and is also the epicentre to many subaqueous earthquakes. As such, the region is an area prone to tsunamis. This investigation uses the Cornell Multi-Grid Coupled Tsunami (COMCOT) tsunami modelling package to simulate five near-field landslides, and five near-field earthquakes regarded as worst-case credible scenarios for Palermo. The seismic simulations produced waves on a very small scale, the largest being c. 5 cm at its maximum height, and none of the earthquake-generated tsunami waves produced any measurable inundation. The landslide simulations produced larger waves ranging from 1.9 to 12 m in maximum height, two of which resulted in inundation in areas surrounding the Port of Palermo. Sensitivity analysis identified that fault width and dislocation as well as landslide-specific gravity did have significant influence over maximum wave height, inundation and maximum run-up wave height. There are methodological issues limiting the extent to which this study forms a comprehensive tsunami hazard assessment of Palermo, such as gaps in bathymetric data, computational restrictions and lack of a probabilistic element. These issues are counteracted by the fact that this study does serve as a robust first step in identifying that landslides in the region may produce larger tsunami waves than earthquakes, and that the directionality of mass movement is critical in landslide-driven tsunami propagation in the southern Tyrrhenian region.

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