Tsunami

A generated water-surface gravity-wave event that propagates from a source disturbance and may produce highly local or distant coastal effects.

Version

v1 · 2026-10-07 · History

Domain-specific #

14040

Domain group

Natural Sciences

Origin domain

Geology & Earth Sciences

Subdomain

Tsunami Science → Geology & Earth Sciences

Core Idea

A tsunami is a generated event of propagating water-surface gravity-wave motion. Seabed displacement, a slide entering or moving under water, and some rapidly moving atmospheric-pressure disturbances can launch such motion. The waves then interact with water depth and basin or shore geometry. Source, propagation and coastal impact are separate roles: an earthquake does not automatically produce a tsunami, and a tsunami does not need to flood a coast before it earns its name.^[1][2]

The 2004 Indian Ocean event and the 1958 Lituya Bay event make this distinction concrete. The former came from a major undersea earthquake and left locally varying wave-height and inundation evidence on northwest Sumatra. The latter followed a rockslide into a confined Alaskan inlet and produced extreme local run-up. They share a propagating water-wave event, but neither source type, travel range nor local height is universal.^[3][4]

Structural Signature

Signature: generating disturbance + water body and geometry + propagating surface-gravity wave → possible, site-dependent shore interaction.

1. Disturbing source. The studied mechanisms are seabed motion and a rockslide; NOAA also describes pressure-forced meteotsunamis. A disturbance must launch the water-level wave, not merely occur near water.^[1]
2. Water body and geometry. Depth and basin or inlet form set pathways and affect speed, reflection, focusing and shore response. The open Indian Ocean and confined Lituya Bay are unlike cases.^[2][3][4]
3. Propagating surface-gravity disturbance. Wave motion travels from source through the water body. A source event or local splash without propagation is insufficient.^[1][4]
4. Shore interaction or observed impact. Field investigators may record wave height, run-up, inundation and damage. This is a consequence and evidence of particular cases, not a requirement that every wave already have made landfall.^[3][4]
5. Regime-bound propagation relation. In a linear long-wave approximation, speed is roughly c ≈ √(gh), with g gravitational acceleration and h water depth; deeper water gives faster travel in that regime. Impact, breaking and overland flow need not obey this simple relation.^[2]

What It Is Not

An astronomical tide is not a tsunami merely because water level rises; “tidal wave” misleadingly suggests the wrong cause. Ordinary sustained wind waves and wind-driven storm surge have different forcing. NOAA also distinguishes a pressure-forced meteotsunami from storm surge or a seiche with which it may be confused. The meteotsunami is a qualified atmospheric subtype within the tsunami family here, not an excluded near miss.^[1]

Nor is a tsunami identical with its triggering earthquake or landslide. A strong earthquake may fail to move enough seabed in the needed way; a slide may make a local wave with limited reach. The wave event is what must be established.^[1]

Scope of Application

The long-wave speed expression models propagation under a depth/wavelength and linearization regime. It is useful for travel-time reasoning in deep water, but not an exact equation for the near-impact Lituya wave or for flooded streets. Small offshore amplitude, little attenuation, an ocean crossing and a particular train of waves are common descriptions of some oceanic cases, not admission conditions for every tsunami.^[2][4]

The Sumatra page reports an initial field survey, including 20–30 m wave-height evidence at the island's northwest end; it is not a uniform Indian Ocean amplitude or a source-slip inversion. Miller's report is a local 1958 bay investigation with eyewitness and physical evidence. Its exceptional run-up is not a template for seismic coastlines elsewhere.^[3][4]

Clarity

Ask three questions in sequence: what disturbed the water, what propagated, and what was observed where? NOAA's mechanism account supports a route from seabed motion to displaced water, while the Sumatra team supplies specific coastal measurements. Miller links a rockslide in Gilbert Inlet to an outward-moving bay wave and shore evidence. Keeping those evidential steps separate avoids attributing a survey height directly to a universal source law.^[1][3][4]

The word wave has a narrower role than the whole event. The internal propagation can be studied as Wave; breaking, run-up and inundation may involve substantial water transport and nonlinear behavior. The entry therefore does not require every part of a tsunami to satisfy an idealized linear no-net-transport description.

Manages Complexity

“Tsunami” groups unlike source mechanisms by a common water-wave event. It lets a field report distinguish generator, propagation path and local impact without forcing all earthquakes, slides or storms into the same geometry. A model can estimate a propagation speed, while a shore survey or eyewitness account establishes what happened at a particular place.^[1][3][4]

That grouping has limits. A source label does not determine one height or warning time. NOAA notes that landslide waves can be high near the source yet lose energy quickly; the Sumatra and Lituya investigations provide different observational scales. Their measurements are not interchangeable calibration points.^[1][3][4]

Abstract Reasoning

To classify a candidate, identify the source disturbance, the water body, and evidence that a surface-gravity disturbance propagated away from the source. Then ask whether the observation concerns open-water propagation, shore arrival or overland flooding. Only after locating the regime should c ≈ √(gh) be used as an approximation. If propagation cannot be established, a rockfall, pressure pulse or local water-level change alone is not enough.^[1][2]

The causal roles also survive a counterfactual test. Remove the water body or the launched wave and the source event remains but the tsunami does not. Remove a documented shore impact and an offshore traveling tsunami may still exist; only one observed consequence has disappeared.^[1]

Knowledge Transfer

The shared pattern transfers between an ocean basin and a narrow bay: forcing enters water, a surface-gravity disturbance travels, and local geometry conditions observed height or run-up. The 2004 field team's numbers cannot be transferred to Lituya, and Miller's run-up cannot be transferred to Sumatra. The long-wave formula transfers only where its approximation is warranted.^[3][4][2]

The live Wave Prime contributes an internal movement skeleton. It is not asserted as a whole-event strict genus because its modeled linear superposition and no-net-medium-transport signature may fail during breaking or inundation. Any wider generated-hazard pattern across media remains a future Prime question, unsupported by these two water-body cases.

Examples

2004 Indian Ocean tsunami at Sumatra

A major undersea earthquake generated a tsunami that reached Sumatra. An international survey team documented wave-height evidence of about 20–30 m at the northwest end of the island, with other findings varying along the coast. The team inspected inundation and damage; its initial account does not turn those local heights into an offshore wave amplitude or a uniform height for the ocean basin.^[1][3]

Mapped back: source → earthquake-related seabed displacement as NOAA's mechanism account; water body → Indian Ocean and northwest Sumatra coast; propagating disturbance → tsunami traveling to the surveyed coast; shore interaction → local 20–30 m evidence; regime relation → deep-ocean long-wave c ≈ √(gh) may frame travel speed, with no case-specific speed inferred.^[2]

1958 rockslide wave in Lituya Bay

An earthquake-triggered rockslide entered Gilbert Inlet. Miller's USGS investigation connected that slide to a giant wave propagating through confined Lituya Bay, using physical tree-damage and shoreline evidence together with eyewitness accounts. The extreme local run-up illustrates what a confined geometry and near-source slide can produce; it does not imply that every landslide tsunami has the same height or travels across an ocean.^[4][1]

Mapped back: source → rockslide into the inlet; water body → confined bay; propagating disturbance → wave moving out through Lituya Bay; shore interaction → local run-up and tree damage; regime relation → the deep-ocean linear speed expression is not imposed on near-impact dynamics.

Structural Tensions

The two cases do not establish an intrinsic tradeoff of the tsunami identity. A useful scope diagnostic is to ask which part of a claimed path or height follows from a propagation approximation and which part was directly surveyed. Sumatra's initial survey and Miller's eyewitness and physical reconstruction answer different local questions; neither supplies a universal coastal-height rule.^[3][4]

Structural–Framed Character

Tsunami is primarily a physical phenomenon. Evaluative weight: destructive impact matters for hazards, but damage is not needed to identify an offshore wave. Human-practice dependence: surveys, warnings and models are human practices; the disturbance propagates without them. Institutional origin: a catalog label does not generate the water motion. Vocabulary travel: metaphorical “tsunami” has none of the required water-wave roles. Import versus recognition: a new event is recognized from source and wave evidence, not inferred from an earthquake label alone. Portable skeleton: propagating disturbance belongs to live Wave as an internal part; a generalized generated-hazard form beyond water remains a future Prime question. Its character: a source-generated water-surface wave event whose impacts depend on site and regime.^[1][3][4]

Structural Core vs. Domain Accent

The core is a generating disturbance that launches a propagating surface-gravity wave in a water body. A source event and water are constitutive, while source type and basin or shore geometry vary: earthquake/ocean in one case, slide/confined bay in the other. A qualified pressure-forced meteotsunami changes the source type without changing the need for a traveling water wave; a sustained wind-driven surge or standing seiche without that wave fails the test.^[1]

The named Tsunami remains domain-specific: every positive instance requires a generated water-surface event, and these water-body cases do not establish an independent cross-domain instance of that identity. The approved typed relation is composition/part_of, with Wave parent_in_child: a propagating wave is an identity-bearing constituent inside the larger event. Removing the wave collapses tsunami identity, while waves of sound, light or ordinary wind can exist without tsunamis. Whole-event subsumption would import the live Wave Prime's idealized linear and no-net-transport constraints into breaking and inundation, which these sources do not warrant.

Instantiates / Related Primes

This entry is part of Wave.

Wave is the approved strict internal constituent. The source event and possible shore response make a tsunami more than its propagating wave component, and Wave exists in many independent settings. Propagation describes the movement but does not replace the generated water-wave event. Flow can describe overland inundation yet is not required as the whole identity. A marine heatwave is a persistent thermal anomaly and lacks this generated traveling surface-gravity event.

Relationships to Other Abstractions

Current abstraction Tsunami Domain-specific

Parents (1) — more general patterns this builds on

• Tsunami is part of Wave Prime

  Propagating water-surface wave motion is an identity-bearing constituent within a tsunami event.

Hierarchy path (1) — routes to 1 parentless root

• Tsunami → Wave

Neighborhood in Abstraction Space

Tsunami sits in a sparse region of the domain-specific corpus (90^th percentile for distinctiveness): few abstractions share its structure, so a faithful description tends to retrieve it precisely.

Family — Unclustered & Miscellaneous (2551 abstractions)

Nearest neighbors

• Wave shoaling — 0.83
• Wind Fetch — 0.81
• Longshore drift — 0.80
• Rossby whistle — 0.80
• Mesoscale Eddy — 0.79

Computed from structural-signature embeddings · 2026-10-08

Not to Be Confused With

An earthquake with no generated water wave; a rockslide with only local splash; ordinary wind waves; storm surge; astronomical tides; or a standing seiche without a launched traveling tsunami. NOAA's meteotsunami is a qualified weather-driven positive subtype, not an exclusion. A particular coastal run-up number is evidence of one event, not the definition of the entire category.^[1][3][4]

References

[1] National Oceanic and Atmospheric Administration, The science behind tsunamis, official explainer, “What is a tsunami?,” “How landslides generate tsunamis,” and “What is a meteotsunami?” sections. The page explicitly distinguishes meteotsunami from storm surge and seiche. registry ↩a ↩b ↩c ↩d ↩e ↩f ↩g ↩h ↩i ↩j ↩k ↩l ↩m ↩n ↩o

[2] National Weather Service JetStream, Tsunami Propagation, official NOAA/NWS module, “Fast Facts” and depth/speed discussion. The text gives the gravity–depth square-root speed; this entry states the linear long-wave regime as the approximation's scope. registry ↩a ↩b ↩c ↩d ↩e ↩f ↩g

[3] Sumatra International Tsunami Survey Team, The 26 December 2004 Indian Ocean Tsunami, Initial Findings from Sumatra, U.S. Geological Survey field report, based on 20–29 January 2005 survey, Introduction and linked Methods/photographs. The source title uses a colon after “Tsunami”; the linked comma is a transcription for full work identity. registry ↩a ↩b ↩c ↩d ↩e ↩f ↩g ↩h ↩i ↩j ↩k ↩l

[4] Don J. Miller, Giant Waves in Lituya Bay, Alaska, U.S. Geological Survey Professional Paper 354-C (1960), printed pp. 63–70 and 72–76; original full report. The report supports rockslide generation and local wave evidence, not a universal run-up magnitude. registry ↩a ↩b ↩c ↩d ↩e ↩f ↩g ↩h ↩i ↩j ↩k ↩l ↩m ↩n