Near-field Tsunami Research Articles

Discrimination of Tsunami Sources (Earthquake versus Landslide) on the Basis of Historical Data in Eastern Sicily and Southern Calabria

Abstract The source mechanisms responsible for large historical tsunamis that have struck eastern Sicily and southern Calabria are a topic of robust debate. We have compiled a database of historical coeval descriptions of three large tsunamis: 11 January 1693, 6 February 1783, and 28 December 1908. By using accounts of run-up and inundation and employing an approach proposed by Okal and Synolakis in 2004, we can provide discriminants to define the nature of the near-field tsunami sources (fault dislocation or landslide). Historical reports for the 1908 event describe affected localities, maximum run-ups, and inundation areas. However, for the 1693 and 1783 tsunamis, reports are limited to inundation and occasional run-up estimates. We calculate run-up values for these events using available relations between inundation and run-up. We employed the model of Okal and Synolakis to the obtained profiles of tsunami run-up along the inundated shorelines. The 1908 run-up data distribution confirms that the tsunami is compatible with a seismic dislocation source, whereas the 1783 data supports contemporary observations and recent offshore investigations suggesting that the tsunami was produced by an earthquake-triggered submarine landslide. Analysis of the 1693 event data suggests that the tsunami was generated during a tectonic event and thus a seismogenic source should be found offshore.

Far field tsunami simulations of the 1755 Lisbon earthquake: Implications for tsunami hazard to the U.S. East Coast and the Caribbean

The great Lisbon earthquake of November 1st, 1755 with an estimated moment magnitude of 8.5–9.0 was the most destructive earthquake in European history. The associated tsunami run-up was reported to have reached 5–15 m along the Portuguese and Moroccan coasts and the run-up was significant at the Azores and Madeira Island. Run-up reports from a trans-oceanic tsunami were documented in the Caribbean, Brazil and Newfoundland (Canada). No reports were documented along the U.S. East Coast. Many attempts have been made to characterize the 1755 Lisbon earthquake source using geophysical surveys and modeling the near-field earthquake intensity and tsunami effects. Studying far field effects, as presented in this paper, is advantageous in establishing constraints on source location and strike orientation because trans-oceanic tsunamis are less influenced by near source bathymetry and are unaffected by triggered submarine landslides at the source. Source location, fault orientation and bathymetry are the main elements governing transatlantic tsunami propagation to sites along the U.S. East Coast, much more than distance from the source and continental shelf width. Results of our far and near-field tsunami simulations based on relative amplitude comparison limit the earthquake source area to a region located south of the Gorringe Bank in the center of the Horseshoe Plain. This is in contrast with previously suggested sources such as Marqués de Pombal Fault, and Gulf of Cádiz Fault, which are farther east of the Horseshoe Plain. The earthquake was likely to be a thrust event on a fault striking ~ 345° and dipping to the ENE as opposed to the suggested earthquake source of the Gorringe Bank Fault, which trends NE–SW. Gorringe Bank, the Madeira-Tore Rise (MTR), and the Azores appear to have acted as topographic scatterers for tsunami energy, shielding most of the U.S. East Coast from the 1755 Lisbon tsunami. Additional simulations to assess tsunami hazard to the U.S. East Coast from possible future earthquakes along the Azores–Iberia plate boundary indicate that sources west of the MTR and in the Gulf of Cadiz may affect the southeastern coast of the U.S. The Azores–Iberia plate boundary west of the MTR is characterized by strike–slip faults, not thrusts, but the Gulf of Cadiz may have thrust faults. Southern Florida seems to be at risk from sources located east of MTR and South of the Gorringe Bank, but it is mostly shielded by the Bahamas. Higher resolution near-shore bathymetry along the U.S. East Coast and the Caribbean as well as a detailed study of potential tsunami sources in the central west part of the Horseshoe Plain are necessary to verify our simulation results.

Community Resilience Roundtable on the Implementation of Homeland Security Presidential Directive 21 (HSPD-21)

Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and ScienceVol. 6, No. 3 Meeting ReportCommunity Resilience Roundtable on the Implementation of Homeland Security Presidential Directive 21 (HSPD-21)Monica Schoch-Spana, Brooke Courtney, Crystal Franco, Ann Norwood, and Jennifer B. NuzzoMonica Schoch-SpanaSearch for more papers by this author, Brooke CourtneySearch for more papers by this author, Crystal FrancoSearch for more papers by this author, Ann NorwoodSearch for more papers by this author, and Jennifer B. NuzzoSearch for more papers by this authorPublished Online:16 Sep 2008https://doi.org/10.1089/bsp.2008.0809AboutSectionsPDF/EPUB Permissions & CitationsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail FiguresReferencesRelatedDetailsCited byAn Approach to the Unified Conceptualization, Definition, and Characterization of Social Resilience9 May 2022 | International Journal of Environmental Research and Public Health, Vol. 19, No. 9Health-Care Services as a Platform for Building Community Resilience among Minority Communities: An Israeli Pilot Study during the COVID-19 Outbreak16 October 2020 | International Journal of Environmental Research and Public Health, Vol. 17, No. 20The Los Angeles County Community Disaster Resilience Project: A Community-Level, Public Health Initiative to Build Community Disaster Resilience31 March 2016An agent-based model of a multimodal near-field tsunami evacuation: Decision-making and life safetyTransportation Research Part C: Emerging Technologies, Vol. 64Use of the Structured Interview Matrix to Enhance Community Resilience Through Collaboration and Inclusive Engagement15 January 2014 | Systems Research and Behavioral Science, Vol. 32, No. 6International Journal of Environmental Research and Public Health, Vol. 11, No. 8The Promise and Pitfalls of Community Resilience18 December 2013 | Disaster Medicine and Public Health Preparedness, Vol. 7, No. 6Building Community Disaster Resilience: Perspectives From a Large Urban County Department of Public HealthAmerican Journal of Public Health, Vol. 103, No. 7Disaster Resilience and People with Functional NeedsNew England Journal of Medicine, Vol. 367, No. 24Citizen Preparedness for Disasters: Are Current Assumptions Valid?8 April 2013 | Disaster Medicine and Public Health Preparedness, Vol. 6, No. 2Resilience thinking in health protection6 April 2011 | Journal of Public Health, Vol. 33, No. 3Major Influences on Hospital Emergency Management and Disaster Preparedness8 April 2013 | Disaster Medicine and Public Health Preparedness, Vol. 3, No. S1 Volume 6Issue 3Sep 2008 InformationMary Ann Liebert, Inc.To cite this article:Monica Schoch-Spana, Brooke Courtney, Crystal Franco, Ann Norwood, and Jennifer B. Nuzzo.Community Resilience Roundtable on the Implementation of Homeland Security Presidential Directive 21 (HSPD-21).Biosecurity and Bioterrorism: Biodefense Strategy, Practice, and Science.Sep 2008.269-278.http://doi.org/10.1089/bsp.2008.0809Published in Volume: 6 Issue 3: September 16, 2008PDF download

Rupture Process of the 18 April 1906 California Earthquake from Near-Field Tsunami Waveform Inversion

Abstract The 18 April 1906 M ∼8 California earthquake generated a small local tsunami that was recorded in the near field by the Presidio, San Francisco tide gauge located near the Golden Gate. We investigate the causative, tsunamigenic, seismic source by forward modeling and nonlinear inversion of the Presidio marigram. We use existing seismological and geological observations to fix the fault system geometry and the surface slip on the onland portions of the San Andreas fault (SAF). We perform synthetic inversions to show that the single, near-field marigram constrains the main features of the rupture on the portion of the SAF system offshore of the Golden Gate. Finally, we perform nonlinear inversions for the slip distribution and the timing of the rupture of the 1906 earthquake. Our results, in agreement with previous studies, identify a dilatational stepover and show a bilateral rupture, possibly originating or propagated through the stepover region. We find that little or no coseismic slip on normal faults in the stepover region is required to fit the marigram, and we obtain adequate fits when allowing delays in the source initiation times of up to 3 min on the various fault segments. We constrain slip to be of about 5–6 m for the onshore portion of the SAF to the northwest of the Golden Gate, in agreement with 1906 surface observations of fault offset. Our results favor the hypothesis of a vertical dip for a currently aseismic SAF to the southeast of the Golden Gate, under the San Francisco peninsula.

Scenarios of tsunami amplitudes in the north eastern coast of Sea of Marmara generated by submarine mass failure

In this paper the tsunamis resulting from a submarine mass failure such as slides and slumps triggered by earthquakes or other environmental effects, which is settled at the bottom of the north eastern Sea of Marmara are examined in one sample region. As the solution method, one hybrid method is developed. The main objective of this method is to combine an analytical solution presenting near-field tsunami amplitudes above the submarine mass failure with a numerical solution indicating the tsunami amplitudes in the coastal regions. For this purpose, one common linear boundary between analytical and numerical solution domains is defined. Movements of Submarine Mass Failures (SMF) are modeled using one simple kinematics source model and the amplitudes of the tsunamis at the region that are closer to the landslide are computed by using the analytical method. SMF is modeled approximately from the bottom geometry, and an average depth is used. Scenarios of SMF are established depending on the velocities and thicknesses of the failure, and near-field tsunami amplitudes are obtained in the open sea during the source time. After the source times, the solutions are found in the numerical region using TELEMAC-2D software system with the mentioned boundary above. In this boundary, the output of the analytical solutions is taken as the boundary conditions or the disturbances for the numerical method. With these disturbances, the numerical method is performed and the amplitudes are calculated in the coastal area. The generation, propagation and coastal amplifications of the tsunamis are illustrated at some certain points and regions both in the open sea and near the coast line. The results have been visualized and discussed.

Upgrade of the Dynamic Simulation Procedure for Near-Field Tsunamis

The 3-D dynamic tsunami simulation procedure developed by the authors takes into account the dynamic seabed displacement resulting from seismic faulting and acoustic effects of seawater. Some new techniques have been developed for upgrade of the existing procedure, which include the so-called nesting of the mesh size and extension for run-up to coastal areas. Practicality of the upgraded procedure has been successfully validated by, for example, simulation of the dynamic generation of a near-field tsunami followed by the propagation and run-up.

Tsunami Hazards Associated with the Perachora Fault at Eastern Corinth Gulf, Greece

We investigate the tsunami hazard associated with the Perachora fault at eastern Corinth Gulf, Greece. Realistic faulting parameters are used to model expected coseismic displacements of the seafloor. This study also investigates the effect that rupture complexity has on the local tsunami wave field. Several earthquake scenarios are used as initial conditions for tsunami stimulation either considering the numerous published constant slip models or taking into account the fault rupture complexity with the help of a realistic finite-extent k 2 stochastic kinematic source model with k-dependent rise time. The obtained results indicate that there is sub- stantially more variation in the local tsunami wave field derived from the inherent complexity of the shallow fault zone than predicted by a simple elastic dislocation model. Rupture complexity, as represented by heterogeneous slip-distribution pat- terns, has an important effect on near-field tsunami records. Tsunami hazards as- sessments based on only a few scenario earthquakes may not accurately account for natural variation in tsunami amplitude caused by earthquake rupture complexity.

The offshore morpho-structure and tsunami sources of the Viti Levu Seismic Zone, southeast Viti Levu, Fiji

New high-resolution SeaBAT 8160 multibeam bathymetry data reveal in detail the complex offshore morphology over part of the Viti Levu Seismic Zone (VLSZ) in southeast Viti Levu. The mapped seafloor is scarred by a complex network of linear submarine canyons and numerous submarine slides. The submarine canyons are morphologic expressions of graben structures in the underlying basement rock. Submarine canyon faults are continuous with nearshore (shelf) faults and onshore fault-controlled valleys and structural lineaments. Together, these define continuous onshore–offshore fault zones, which combined form a structurally complex fault mesh of composite origin. We attribute the development of the principal fault sets in the fault mesh to progressive distributed faulting in response to anticlockwise tectonic block rotations within the Fiji Platform during the Neogene. Low occurrence of large earthquakes, and a diffused pattern of seismicity currently observed in the VLSZ, may reflect complex coseismic faulting through the fault mesh. The abundance of submarine slides over the VLSZ, which typically occur on the outer barrier reef edge, as well as the submarine canyon heads and walls, and mid-slope, imply that seismic shaking may be an important factor for triggering slope failure. Morphometric analysis and empirical modelling of the slides show that slides triggered in shallow water depths, within 5 km of the coastline, at the outer barrier reef edge, and submarine canyon heads, produce the largest near-field tsunami amplitudes. We interpret that such slides represent a significant local tsunami hazard.

The near-field tsunami amplitudes caused by submarine landslides and slumps spreading in two orthogonal directions

The aim of this study is to present the solutions for the near-field tsunami amplitudes caused by submarine landslumps and slides spreading in two orthogonal directions. A linearized shallow water wave theory is derived. The transform techniques (Fourier and Laplace transform) are used for the solution of Laplace equation. The results show that if the ratio of the velocties is v 1/ v 2=0.1, the numerical results are almost the same as the values obtained for one dimensional movement of the slumps and slides. But, when the ratio of the velocties is v 1/ v 2=1, obtained normalized peak amplitudes, η max/ ζ 0 are smaller than the numerical values for one dimensional solution. It is concluded that normalized peak amplitudes for the models are small because of the interaction of the velocities. Numerical examples are presented for various parameters.

Source discriminants for near-field tsunamis

We present numerical simulations of tsunami run-up in the near field for a data set of 72 models of sources, involving both seismic dislocations and landslides. By varying one by one the parameters describing the source and the receiving beach, we are able to separate their individual influence on the amplitude and distribution of run-up, which we characterize by forming several dimensionless parameters, principally the ratio I2 of its maximum amplitude to its lateral extent along the beach. We find that I2 remains less than 10−4 for seismic dislocation sources but is greater than this threshold for all physically realistic models of underwater landslides. Thus, it can be used as a discriminant for the nature of the source of a near-field tsunami. For seismic dislocations, we also consider the ratio I1 of maximum run-up to seismic slip on the fault plane, and validate numerically the previously suggested ‘rule of thumb’ that this ratio cannot be much greater than 1. In the case of underwater landslides, we show that the distribution of near-field run-up is primarily controlled by the 2-D ‘wall of water’ displaced on the ocean surface as an initial condition to the simulation, and is practically independent of its extension in the third dimension, perpendicular to the beach. We apply this approach to nine profiles of tsunami run-up obtained experimentally during recent field surveys, and show that our method successfully identifies the 1998 Papua New Guinea tsunami as having been generated by an underwater landslide, thus confirming the results of shipboard and hydroacoustic investigations. It also strongly suggests a similar mechanism for the generation of the near-field Aleutian tsunami of 1946 April 1.

A re-analysis of the Late Bronze Age eruption and tsunami of Santorini, Greece, and the implications for the volcano–tsunami hazard

The paroxysmal eruption of Santorini (ca. 3500 BP), referred to as the Late Bronze Age (LBA) eruption, probably generated multiple tsunami; their occurrence and impacts being cited frequently in scientific papers and articles. This paper examines what is known about any LBA tsunami, noting possible mechanisms of generation and identifying sedimentological traces. Firstly, the eruption sequence is outlined providing the context in which tsunami genesis may have occurred. Secondly, the arguments forwarded for the tsunami and a summary of the evidence is given. Thirdly, results of a new geological investigation for LBA tsunami deposits at 41 coastal sites from Crete and Kos are presented. The data are used to test the hypothesis that the LBA eruption generated an east Mediterranean-wide tsunami. It will be seen that no terrestrial geological evidence is identified. The paper re-examines the original arguments presented for LBA tsunami, challenging them because their founding assumptions are flawed. Together, the new data and the re-analysis of the original tsunami hypothesis indicate that there is insufficient evidence to demonstrate that any significant far-field tsunami propagated throughout the entire east Mediterranean as frequently purported. Some terrestrial evidence exists to suggest localised near-field tsunami inundation. There is good submarine evidence however, to suggest that a tsunami was focused to the W and WSW. The results have important implications for understanding the volcano-related tsunami hazard within the region and elsewhere.

The effects of variable speeds of a submarine block slide on near-field tsunami amplitudes

In this study, the motion of a submarine block slide, with variable velocities, and its effects on the near-field tsunami amplitudes are investigated. The numerical results show that the amplitudes generated by the slide are almost the same as those created by its average velocity when c ̄ /c T>5 , where c̄ is average velocity of the slide and c T= gh is the long period tsunami velocity in ocean of constant depth h. In contrast, the kinematic model of the slide must take into account time variations in the moving velocity, if c ̄ /c T≤5 , especially when c ̄ /c T∼1 .

A note on the effects of nonuniform spreading velocity of submarine slumps and slides on the near-field tsunami amplitudes

The effects of variable speeds of spreading of submarine slides and slumps on near-field tsunami amplitudes are illustrated. It is shown that kinematic models of submarine slides and slumps must consider time variations in the spreading velocities, when these velocities are less than about 2 c T, where c T = gh is the long period tsunami velocity in ocean of constant depth h. For average spreading velocities greater than ∼2 c T, kinematic models with assumed constant spreading velocities provide good approximation for the tsunami amplitudes above the source.

Numerical Simulation as a Means of Warning for Near-Field Tsunamis

ABSTRACTThe feasibility of quantitatively forecasting a near-field tsunami prior to its arrival is examined, provided that the initial tsunami profile can be determined from fault parameters calculated using a method similar to that of Izutani and Hirasawa. Examination of basic equations, boundary conditions and grid lengths has led to the conclusion that the following combination is the best to perform rapid, accurate, and detailed numerical forecasting; the linear long wave theory discretized with the staggered leap-frog scheme, perfect reflection at the land boundary, and a grid length varying from 5.4 km out at deep sea to 0.2 km at the shoreline. With the aid of a super computer, tsunami heights along every 200 m of Japan's Sanriku coast (250 km long) can be obtained within 7 minutes after the occurrence of an earthquake. This method gives enough time for warning transmission and for evacuation of residents because the standard arrival time of tsunamis in this district is 25 to 30 minutes.

Effects of bathymetry on tsunami propagation: Application of ray tracing to tsunamis

Ray tracing of seismic surface waves is applied to tsunami propagation to examine bathymetric effect along its propagation path. Computations are made for trans-Pacific tsunamis and for near-field tsunamis in the Japan Sea. For tsunamis across the Pacific Ocean, the comparison to a uniform ocean shows that focusing and defocusing, due to bathymetry, are significant for some combinations of source and receiver. For example, the refraction of rays is predominant at the East Pacific Rise for the tsunami from Chile. The tsunamis in the Japan Sea are strongly affected by the shallow Yamato Rise. The predicted arrival time and amplitude distribution generally agree with the observations from an actual tsunami. Since the computation can be made very quickly, the method is useful for preliminary analysis of tsunami propagation, such as in an operational warning system or in the determination of computational area for finite-difference computation.

Use of strong motion duration for rapid evaluation of fault parameters.

A simple method is developed for rapid determination of fault parameters of a large shallow earthquake from the azimuthal dependence in duration of strong ground motion. The fault length and the direction of rupture propagation can be evaluated by this method within a short time after the earthquake origin time. As an example, the fault parameters are determined for the Tokachi-Oki earthquake of May 16, 1968. They are consistent with the main rupture process revealed by other investigators from far-field long-period seismic records, near-field strong motion records and aftershock distribution. Thus, the present method may be applicable to near-field tsunami warning, provided that a sufficient number of digital accelerographs are installed with a good azimuthal coverage.