Tsunamis in Japan are a frequent natural phenomenon due to the country's unique geological setting. Situated along the Pacific Ring of Fire, Japan is prone to powerful underwater earthquakes, which often trigger tsunamis. These tsunamis can cause significant damage to coastal communities and infrastructure, making preparedness and awareness crucial for residents and authorities alike.
What is a Tsunami?
Before preparing for a tsunami, you need to understand what a tsunami is. The word "tsunami" originates from Japanese, where "tsu" (津) means "harbor" and "nami" (波) means "wave." When combined, "tsunami" translates to "harbor wave" or "seismic sea wave." The term is a testament to Japan's historical encounters with these powerful ocean waves and reflects the country's long-standing awareness of the phenomenon.
A tsunami is a series of powerful ocean waves caused by underwater disturbances, typically earthquakes, volcanic eruptions, or landslides. When these events occur beneath the ocean floor, they displace massive amounts of water, generating a series of waves that can travel across entire ocean basins.
Tsunami waves are different from regular ocean waves. While ocean waves are driven by wind and have relatively short wavelengths, tsunamis have much longer wavelengths and travel at high speeds across the ocean surface, often reaching speeds of 500 to 600 miles per hour (800 to 1,000 kilometers per hour) in deep water.
As a tsunami approaches shallow coastal areas, its speed decreases, but its energy becomes concentrated, causing the wave to grow dramatically in height. This can result in devastating flooding and destruction when the waves reach land, especially in low-lying coastal regions.
Three types of Tsunami Warning
In Japan, tsunami warnings are issued by the Japan Meteorological Agency (JMA) to alert residents about potential tsunamis and guide them on appropriate actions to take. These warnings are categorized into three levels: Tsunami Warnings, Tsunami Advisories, and Tsunami Watches. Each level corresponds to different expected tsunami heights, potential damage, and recommended actions:
1. Tsunami Warnings (Tsunami Keihō, 津波警報)
Expected tsunami height: 3 meters and up
Potential damage: Tsunami warnings indicate the potential for extensive inundation, flooding, and damage to coastal infrastructure, buildings, and communities. There is a high risk of loss of life and property damage.
What to do: Evacuate immediately to high ground and follow instructions from local authorities.
2. Tsunami Advisories (Tsunami Chūihō, 津波注意報)
Expected tsunami height: 1 meter - 3 meters
Potential damage: While tsunami advisories indicate a lower risk compared to tsunami warnings, there is still potential for localized flooding, coastal erosion, and minor damage to infrastructure. People will get caught in tsunami currents.
What to do: Evacuate immediately to high ground and follow instructions from local authorities.
3. Tsunami Watches (Tsunami Keiho, 津波予報)
Expected tsunami height: 20 centimeters - 1 meter
Potential damage: Small tsunamis can cause boats and vessels to break free from moorings or be washed ashore, resulting in damage to maritime infrastructure, including docks, piers, and marinas. It also can generate powerful currents and surges that pose risks to swimmers, surfers, and coastal residents. These currents can drag people and objects out to sea or cause injuries and drownings in turbulent waters.
What to do: Get out of the water immediately and leave coastal areas.
What to Do When a Tsunami Happens
Being prepared and responding correctly to natural disasters is crucial because just a few seconds can make all the difference between life and death. Here are some essential safety measures to take when a tsunami strikes.
1. Find information immediately
If you're experiencing a strong earthquake in Japan, it's absolutely crucial to assess the possibility of a tsunami right away. Keep an ear out for alerts or warnings broadcasted by the Japan Meteorological Agency (JMA) on television, radio, mobile notifications, or sirens. These updates will provide essential guidance on evacuation protocols and designated safe zones, ensuring swift and informed action during this critical time.
When you're at the beach, it's essential to keep an eye out for the tsunami flag. Sometimes, you might not feel the earthquake or hear the sirens, so spotting the flag quickly is crucial. When you see the flag, move promptly to an area or building marked with safe refuge signs. Getting familiar with these important signs and signals when you visit the beach can significantly boost your awareness of safety and readiness.
2. Don't wait
If you’re in a coastal area, do not wait for visual confirmation of a tsunami before evacuating. Before the arrival of a tsunami, there is often a phenomenon known as the "drawback," where the water recedes from the shoreline. However, this occurrence may not always be easily noticeable. Tsunamis can arrive within minutes of a triggering event, leaving little time for hesitation.
3. Evacuate to a higher place, not farther
During a tsunami, it's crucial to evacuate to higher ground rather than moving far away from the coast. Tsunami waves can exceed the predicted height mentioned in the warning, making it essential to seek elevated areas for safety. Therefore, aiming for higher ground is the best course of action to ensure your safety during a tsunami event.
4. Get out of the car
Avoid driving through flooded roads or areas affected by tsunami inundation. Floodwaters may be deeper and more dangerous than they appear, posing risks to both you and your vehicle. Additionally, you could become trapped inside your car, as it may be challenging to open the door against the current.
5. Follow evacuation routes
Familiarize yourself with evacuation routes and assembly points in your area. Use designated evacuation routes and follow instructions from emergency responders.
6. Don't return prematurely
After evacuating, do not return to coastal areas until authorities have officially declared it safe to do so. Tsunamis typically consist of a series of waves, rather than just a single wave. This first wave is usually not the largest but serves as an indicator of the tsunami's arrival. The interval between successive waves in a tsunami series can vary, with some waves arriving minutes apart and others arriving much later. Even after the first wave passes, the threat may persist, as subsequent waves can bring additional flooding and destruction to coastal regions.
Rushing back prematurely could expose individuals to further risks and hamper ongoing rescue and recovery efforts. Thus, patience and adherence to official directives are essential for ensuring personal safety and minimizing potential harm in the aftermath of a tsunami.
7. Save yourself first
Japan advises individuals to prioritize their own safety and evacuate immediately when a tsunami warning is issued, rather than waiting to confirm the safety of others. This recommendation is based on lessons learned from past tsunami disasters, including the Great East Japan Earthquake and Tsunami of March 11, 2011.
During the 2011 tsunami, many individuals hesitated to evacuate because they were waiting for confirmation of the safety of family members or waiting to reunite with loved ones before evacuating. Unfortunately, this delay resulted in numerous casualties as the tsunami waves struck coastal areas with devastating force.
As a result, Japan has since emphasized the importance of immediate evacuation to higher ground or designated shelters when a tsunami warning is issued, even if it means evacuating alone. By prioritizing personal safety and following evacuation procedures promptly, individuals can reduce their risk of injury or loss of life during tsunami emergencies.
Japan's proactive approach to tsunami preparedness serves as a model for coastal regions worldwide. With advanced early warning systems, resilient infrastructure, and extensive public education efforts, Japan has significantly reduced the impact of tsunamis on its communities. However, tsunamis are still dangerous, so everyone needs to keep being careful and ready. By staying informed, getting ready, and helping each other, Japan is working hard to stay safe when tsunamis happen.
