Tsunami evacuation, for travellers

The natural-warning rule

One rule has saved more lives in modern tsunami events than any official warning system: if you feel a long, strong earthquake on or near the coast, do not wait for a siren. Move inland or to higher ground immediately. This is the single most important sentence in this guide. The 2004 Indian Ocean tsunami and the 2011 Tōhoku tsunami both killed tens of thousands of people who waited for an official warning that arrived too late, was not loud enough, or never came at all. The travellers who survived on the coast in both events were those who recognised a natural-warning signal and acted within minutes of the shaking stopping, without instruction.

The natural-warning signals, in order of how decisive they are:

• A long, strong earthquake on or near the coast: shaking that lasts 20 seconds or more, strong enough that standing is difficult, with your feet visibly on coastal land. This is the most reliable trigger because most large tsunamis are generated by subduction-zone earthquakes near the coast, and the wave moves more slowly than the seismic signal.
• The sea drawing back unusually far: water receding hundreds of metres in seconds, exposing reef and seabed, with a roaring sound. This means the leading trough of the tsunami is at the coast, and the crest is minutes behind. Do not stop to look. Do not stop to photograph. Move. The 2004 Indian Ocean tsunami killed thousands of people who stayed on the beach to watch this exact phenomenon.
• A loud roaring sound from the sea, often described as resembling a freight train or jet engine.
• Any animal-behaviour anomaly at the coast (animals moving inland, birds taking flight in unusual numbers). Less reliable than the above but historically a documented precursor.

The official warning systems described later in this guide matter. They are how tsunami threats from distant-source earthquakes (thousands of kilometres away) get to you in time. But for near-field tsunamis, the wave can arrive within 10 to 30 minutes of the earthquake, sometimes faster. The natural-warning rule is your only practical defence in that window.

What a tsunami actually is

A tsunami is not a wind-driven surface wave. It is the entire water column moving as a long-wavelength pulse, with hundreds of kilometres of horizontal extent and water that just keeps arriving for tens of minutes. The relevant misconceptions worth unwinding:

• There is rarely one wave. A typical major tsunami has 3 to 8 distinct waves arriving over 2 to 12 hours. The first is often not the largest. The 1960 Valdivia Chile tsunami caused most of its Hawaii fatalities on the third wave, hours after the first.
• The drawback is not always the first sign.Tsunamis from negative leading-trough sources show drawback; tsunamis from positive leading-crest sources arrive directly as a wall of water with no withdrawal warning. Roughly half of tsunamis show the dramatic drawback that is widely documented.
• The wave height at sea is small. In open ocean, a tsunami may be 30 to 60 cm of swell, undetectable from a ship. The water mass becomes catastrophic only at the coast when it shoals.
• Run-up is variable. A 2 m offshore wave can run up to 20 m where coastal bathymetry and shape concentrate it. The 2011 Tōhoku run-up reached 38.9 m at Miyako. The 2004 Indian Ocean run-up exceeded 30 m in parts of Aceh.
• Inundation distance is variable. A tsunami can travel 1 to 3 km inland on flat coast; up to 5 to 10 km in low-lying river valleys. The wave does not respect coastal cliffs, but it does follow coastal valleys.

The Field Manual’s earthquake guide covers what to do during the shaking itself. The transition from earthquake response to tsunami response is the critical moment: when the shaking stops, the question shifts from “am I inside a building that’s about to fall” to “am I on land that’s about to be submerged.”

Warning centres by ocean basin

The international tsunami-warning system is a network of regional centres operating under the UNESCO-IOC Intergovernmental Oceanographic Commission framework. The relevant centres for travellers, by ocean basin:

• Pacific Tsunami Warning Center (PTWC, Honolulu): covers the Pacific basin (Hawaii, US West Coast, Pacific islands, the Central American and South American Pacific coast, Pacific Asia, Pacific Russia). Bulletins for any Pacific-basin earthquake above M6.5 are issued within minutes.
• National Tsunami Warning Center (NTWC, Palmer Alaska): covers the US Pacific coast and Hawaii, US Atlantic, Gulf of Mexico, Caribbean, and Alaska. The local-source response for US coastlines runs from NTWC.
• Indian Ocean Tsunami Warning and Mitigation System (IOTWMS): the multi-country network created after the 2004 Indian Ocean tsunami. Regional Tsunami Service Providers are India (INCOIS), Indonesia (BMKG), and Australia (Joint Australian Tsunami Warning Centre). Coverage: Indian Ocean basin including East Africa, South Asia, Southeast Asia.
• JMA Earthquake and Tsunami Information: Japan issues some of the fastest tsunami warnings in the world, typically within 3 to 5 minutes of a strong coastal earthquake. JMA classifies into Major Tsunami Warning, Tsunami Warning, and Tsunami Advisory.
• SHOA (Chile): the Chilean Navy Hydrographic and Oceanographic Service, the national tsunami authority for the Chilean coast. Has the fastest response on the Eastern Pacific subduction zone.
• GeoNet (New Zealand): operates the Long-or-Strong rule as official guidance: a long earthquake or a strong earthquake at the coast means move to higher ground without waiting for a warning.
• NEAMTWS (North-Eastern Atlantic and Mediterranean and connected seas): covers the Mediterranean, Adriatic, Black Sea, and Northeast Atlantic. Active since 2005 with Tsunami Service Providers in Turkey, Greece, France, Italy, and Portugal.

For most travellers the practical interface with this system is: install the relevant country app (NOAA Weather, JMA Bosai, the Indonesian BMKG app, the Smartraveller TravelHealthPro app, the GeoNet app for New Zealand) before flight, and respect the push-notification alerts when they fire. The MAGMA Indonesia app on the BMKG side delivers volcano and tsunami alerts on a single channel for the Sunda Arc.

Country signage

Coastal evacuation signage varies dramatically by country. Recognising the pictogram on arrival means you do not have to parse it under stress.

• The UNESCO-IOC standard pictogram: a person running uphill above a wave-line, often blue and white. Used in much of Southeast Asia and the Pacific.
• Japan: the “tsunami evacuation building” (津波避難ビル, tsunami hinan biru) sign is a building with a wave and arrow indicating shelter inside; the “tsunami evacuation route” sign is the arrow with a wave-and-person combined. Vertical evacuation (going to the upper floors of a reinforced concrete building) is officially accepted in Japan when horizontal evacuation to high ground is not possible within the warning window.
• United States: blue and white signs on the Pacific and Caribbean coasts. The Tsunami Hazard Zone signs mark where evacuation begins; Tsunami Evacuation Route signs direct the path inland.
• Chile: SHOA-issued signs in cyan and white mark the evacuation route (vía de evacuación) and the safe zone (zona de seguridad). Most coastal Chilean municipalities have visible signage at every block in the coastal flat zone.
• Indonesia: BMKG-issued signs in blue and yellow, often paired with sirens. Tourist areas in Bali, Java, Sumatra, Sulawesi, and Lombok have varying coverage.
• New Zealand: GeoNet/MCDEM signs in blue and white, often with the Maori word for tsunami (ngaru). The Long-or-Strong rule is taught in schools and posted at coastal community centres.

The practical habit when arriving at any coastal accommodation: walk the evacuation route from your room to the marked safe zone within the first 24 hours. You will then know the fastest path under stress.

Where to go

The decision rule is simple even if execution is hard.

• Higher ground: ideally 30 m elevation, or 3 km inland on flat coast. Most coastal evacuation maps mark named safe zones at these thresholds.
• Vertical evacuation: if higher ground is not reachable within the warning window, the upper floors of a reinforced concrete or steel-framed building 4 stories or higher count as functional shelter. Older wood-frame or unreinforced masonry buildings do not. The Japan post-Tōhoku review showed that vertical evacuation in qualifying buildings was effective; vertical evacuation in inadequate buildings was not.
• Do not return to the coast for hours: the multi-wave structure means the second or third wave can be larger than the first. Wait for the all-clear from the official source. Conservative rule: 12 hours from first wave for distant-source events; 8 hours for near-source.
• Do not drive if traffic is gridlocked: in Tōhoku, many fatalities occurred in cars stuck in evacuation traffic. If you can run or walk to high ground, do that.

Atypical tsunamis

Not all tsunamis come from subduction-zone earthquakes. Three atypical sources matter operationally:

• Volcanic tsunamis: the 2022 Hunga Tonga-Hunga Haʻapai eruption produced an atmospheric pressure-wave-driven tsunami that reached Pacific coasts unusually fast and atypically (the warning chain partly failed because models were not tuned for this source). The 2018 Anak Krakatau flank-collapse tsunami killed 430 people in Indonesia’s Sunda Strait without any preceding earthquake. Volcanic tsunamis often arrive without the natural-warning earthquake signal; respect any sea-side anomaly near an active volcano.
• Landslide tsunamis: rare but devastating. The 1958 Lituya Bay landslide-tsunami in Alaska produced the highest measured run-up in history (524 m). Active landslide-prone coasts in Greenland and Norwegian fjords carry monitored risk.
• Submarine landslide tsunamis triggered by offshore earthquakes that themselves are too small to trigger warnings. The 1998 Papua New Guinea tsunami (Sissano lagoon, around 2,200 dead) was the canonical case. Modern warning systems include some submarine-landslide modelling but coverage is incomplete.

Hotel and accommodation decision logic

For travellers booking coastal accommodation in tsunami-exposed regions, the operational checklist:

• Floor selection: above the third floor of a reinforced concrete building is functionally vertical-shelter- ready. Ground floor and first floor in tsunami zones are not.
• Coastal hotel structural type: post-2005 (or post-2011 in Japan) constructions in tsunami zones are built to enhanced standards. Older beachfront properties in some developing-country coasts are not. Read the hotel’s tsunami-evacuation plan posted on the back of the room door; its absence is itself an information signal.
• Evacuation route walk-through: on day one, walk from your room to the marked safe zone. Time it. Note the alternatives.
• Phone setup: install the country’s official warning app and enable critical alerts. Disable do-not-disturb override for alert categories. Some apps allow specifying your accommodation address for geo-targeted warnings.
• Group rendezvous point: if travelling with family, agree the rendezvous point at the safe zone in advance. Do not waste evacuation time searching.

After the wave

The 72-hour post-tsunami environment is hazardous in ways travellers usually do not anticipate.

• Multiple waves: covered above. Do not return until the official all-clear.
• Aftershocks: subduction-zone megathrust events generate hundreds to thousands of aftershocks over days to weeks, some of which can themselves generate secondary tsunamis. The Field Manual’s earthquake guide covers the protocol.
• Contaminated water: salt water, sewage, fuel, chemicals, debris. Do not wade unnecessarily. Open wounds are at high infection risk.
• Structural hazards: weakened buildings, collapsed roads, exposed power lines, unstable debris fields. Movement is risky even after the water recedes.
• Communications collapse: mobile networks saturate or fail. SMS messages often get through when voice calls do not. Satellite messengers (Garmin inReach, Apple Emergency SOS via satellite on iPhone 14+) are the practical family-contact channel in widespread infrastructure failure.
• Consular registration: if you are registered with your country’s travel-registration system (U.S. STEP, UK GOV.UK travel-registration, Smartraveller etc.) you will be notified and prioritised for any consular evacuation. Worth doing on arrival for any tsunami-exposed destination.

The coastal traveller go-bag

A minimal grab-and-run bag for tsunami-zone coastal stays. It fits in a small backpack and lives at the hotel-room door.

• Passport in a waterproof pouch (Ziploc works).
• One credit card and around USD 100 to 200 in local cash.
• Charged phone with battery pack (10,000 mAh sufficient for 2 days).
• Bottled water (1 L per person minimum).
• One change of dry clothing and sturdy walking shoes (which you wear when sleeping in high-risk windows).
• Headlamp or torch.
• Whistle (for signalling in debris).
• Basic medication you cannot do without for 72 hours.
• Photocopy of insurance documents and family contact numbers (paper, in case phone is lost).

Country brief

The Safe Trip country guides cover tsunami-specific risk by destination. The countries with the highest tsunami exposure where most travellers go:

• Japan: world-class JMA warning system; the Tōhoku 2011 reference event still shapes current practice; well-signed evacuation infrastructure along most coasts.
• Indonesia: BMKG InaTEWS warning system; 2004 Indian Ocean, 2018 Sulawesi, 2018 Anak Krakatau reference events; Sunda Arc subduction zone exposure across Sumatra, Java, Bali, Lombok, the Lesser Sundas.
• Chile: SHOA warning system; 1960 Valdivia M9.5 reference event (largest instrumentally recorded earthquake in history); 2010 Maule and 2014 Iquique recent events; well-signed coastal evacuation.
• Peru: Pacific subduction zone; 1996 Chimbote and 2007 Pisco recent events; coastal evacuation maps less consistently maintained than Chile.
• Philippines: Pacific and Sulu Sea exposure; 1976 Moro Gulf reference event; PHIVOLCS monitoring.
• Thailand: 2004 Indian Ocean reference event in Phuket and Khao Lak; warning infrastructure substantially improved since.
• United States: ShakeAlert + NTWC; Pacific coast and Caribbean exposure; local-source response infrastructure varies by state.
• Greece: Hellenic arc subduction; 1956 Amorgos reference event; NEAMTWS coverage.
• Türkiye: Hellenic arc on the southern coast; 2020 Samos-Izmir event affecting Izmir with limited local tsunami impact; NEAMTWS coverage.

One more time

The single sentence that matters: if you feel a long, strong earthquake on or near the coast, do not wait for a siren, head inland and uphill immediately. Walk your evacuation route on arrival. Install the country’s warning app before flight. Stay above the third floor of reinforced-concrete coastal hotels in exposed zones. Wait 12 hours after a distant-source event and 8 hours after a near-source event before returning to the coast. Respect the atypical sources (volcanic and landslide tsunamis) that arrive without the standard earthquake precursor. The Field Manual’s earthquake guide covers the during-shaking response that precedes everything here.