A tsunami is a series of ocean waves caused by large-scale disturbances that displace a significant volume of water, most commonly originating from underwater earthquakes. While these powerful natural phenomena can be incredibly destructive, survival is possible under certain circumstances and with proper knowledge and prompt action. Understanding how to prepare for them can significantly increase one’s chances of safety by recognizing natural signs and knowing effective response strategies.
Key Factors for Survival
The ability to survive a tsunami is influenced by several external and environmental factors. Warning time, from official alerts or natural indicators, is one such factor. Natural signs include feeling a strong earthquake, observing a sudden ocean recession, or hearing a loud roar from the sea. These warnings often precede official alerts, especially for tsunamis generated close to the coastline.
Location and elevation play a significant role in determining exposure to tsunami waves. Being on high ground, ideally at least 30 meters (100 feet) above sea level and several kilometers inland, offers a higher degree of safety. Many at-risk areas are less than 7 meters above sea level and within 2 kilometers of the shoreline, making them highly vulnerable. Even a slight increase in elevation or distance from the coast can improve survival prospects.
The characteristics of tsunami waves, including their height, force, and the number of waves, impact survival. Tsunamis are not single waves but a series, often called a “wave train,” with subsequent waves potentially larger than the first. In the deep ocean, tsunami waves have long wavelengths and small heights, making them imperceptible. As they approach shallower coastal waters, their speed decreases, and their height can increase dramatically, sometimes reaching tens of meters. The force of these waves, combined with debris, contributes to their destructive power.
The structural integrity of available buildings or shelters also influences survivability. Structures built with reinforced concrete or steel framing offer better resistance to tsunami forces than wood construction. Buildings designed with elevated foundations or pilings, or those with breakaway walls on lower floors, allow water to flow through, reducing the impact. Multi-story concrete buildings can also serve as vertical evacuation sites if reaching high ground is not an immediate option.
Preparing and Responding to a Tsunami
Proactive preparation and a swift response increase survival chances when a tsunami threatens. Before a tsunami, understanding local risks is key. Individuals in coastal areas should identify if their area is prone to tsunamis and familiarize themselves with local hazard maps. Knowing the street’s height above sea level and its distance from the coast helps assess personal risk.
Developing and regularly practicing an evacuation plan is important for everyone in a tsunami-prone area. This plan should include designated routes to safe zones, ideally high ground at least 30 meters (100 feet) above sea level or 1 to 2 miles inland. Practice evacuation routes on foot, as roads may become impassable due to congestion or damage. Identify a meeting spot if family members become separated during an evacuation.
Preparing an emergency kit ensures access to supplies during and after a tsunami. This kit should contain:
At least a three-day supply of water (one gallon per person per day) and non-perishable food.
A comprehensive first-aid kit.
A flashlight with extra batteries.
A battery-powered or hand-crank radio.
Important documents in a waterproof container.
Personal hygiene items, a multi-tool, and sturdy shoes.
Recognizing natural warnings is vital, as these signs may precede official alerts and offer minutes for evacuation. If a strong earthquake is felt (especially one lasting 20 seconds or more), or if the ocean recedes unusually far exposing the seabed, evacuate immediately. A loud, unusual roar from the ocean, similar to a train or jet aircraft, also indicates an approaching tsunami. Upon observing any of these signs, begin evacuation without waiting for official orders.
During a tsunami, immediate and decisive action is crucial. If an earthquake occurs, protect yourself by dropping to the ground, covering your head and neck, and holding onto sturdy furniture until the shaking stops. Once the shaking subsides, or upon observing any natural warning signs, move to safety. Evacuate inland to the highest ground possible, preferably on foot, as quickly as circumstances allow.
If caught in the water, focus on survival techniques. Do not attempt to swim against the powerful currents; this is generally not feasible due to the force and debris. Instead, find a flotation device, such as sturdy debris or a tree trunk, to stay afloat. Avoid power lines and other dangerous objects. Remain on high ground until authorities issue an “all clear” message, as tsunamis consist of multiple waves that can arrive over several hours, and the first wave is not always the largest.
Navigating the Aftermath
After the immediate danger of tsunami waves has passed, continued safety and recovery efforts are the priority. Stay informed by listening to official alerts and emergency broadcasts from local authorities via radio or television. Limit non-emergency phone calls to keep communication lines open for response efforts.
Assess damage and ensure personal safety. Check yourself and others for injuries and administer first aid as needed. Stay away from damaged buildings, roads, and bridges, as they may be unstable or contain hidden hazards. Report downed power lines and broken utility lines to authorities; they pose electrocution risks.
Help others only if it is safe. Call professional rescuers for trapped individuals. Health and safety concerns arise in the aftermath, particularly related to water quality. Floodwater can be contaminated with sewage, chemicals, and debris, posing risks of infectious diseases and injuries. Contaminated drinking water sources, including wells inundated by brackish (salt) water, can lead to dehydration and waterborne illnesses like cholera and diarrhea. Avoid wading in floodwaters and consume only bottled or purified water. Emotional trauma can also affect survivors; seeking mental health support is important for recovery.