A tsunami is a series of powerful ocean waves, most often caused by a sudden displacement of the seafloor from a large underwater earthquake, or potentially by landslides or volcanic activity. These waves travel across entire ocean basins at high speeds, gaining immense height and destructive energy as they reach shallow coastal areas. Because a local tsunami can strike within minutes, proactive preparation is the most reliable defense for those in coastal regions. Understanding local risks and having a clear, practiced plan empowers residents to take immediate, life-saving action.
Establishing a Comprehensive Tsunami Safety Plan
The foundation of tsunami safety is a well-considered plan established long before any immediate threat emerges. Begin by determining if your home, workplace, or frequently visited areas are located within an official tsunami hazard zone. Local emergency management agencies often provide detailed inundation maps that clearly delineate these areas.
Once you know your risk, map out multiple evacuation routes to a designated safe area, ideally located at least 100 feet above sea level or 2 miles inland. Practice walking these routes, as roads may become impassable due to traffic or damage during an event. The goal is to reach safety on foot within 15 minutes of an alert.
Compiling a detailed emergency kit is another preparatory step, ensuring you have supplies to be self-sufficient for a minimum of three days. This kit should include non-perishable food, water (one gallon per person per day), and necessary prescription medications. Also pack a battery-powered or hand-crank radio for official updates, essential tools like a flashlight and first-aid kit, copies of important documents, and cash.
Establish a family communication plan that includes an out-of-state contact, as local phone lines may be overwhelmed or damaged. Designate primary and secondary meeting places outside the hazard zone where family members can reunite if separated during an evacuation. Signing up for local government alert systems, which use text messages or email, ensures you receive timely official warnings.
Immediate Response to Official and Natural Warnings
Survival often depends on the speed of reaction to the first sign of danger, whether it is an official bulletin or a natural phenomenon. The most immediate and reliable warning for a local tsunami is often the earthquake that caused it. If you are near the coast and feel strong ground shaking that lasts for 20 seconds or more, you must immediately move to high ground without waiting for an official alert.
Recognize the natural signs of an approaching tsunami, which include an unusual, rapid receding of ocean water that exposes the sea floor, or an audible roar that sounds like a train. If you observe any of these phenomena, regardless of whether an official warning has been issued, start moving inland or uphill immediately. The first wave may arrive within minutes.
Official alerts are issued in escalating levels of severity. A Tsunami Watch means a tsunami is possible; stay alert for updates and prepare to evacuate. A Tsunami Advisory indicates dangerous currents and waves are expected, but widespread flooding is not anticipated, so stay out of the water and away from beaches. The highest alert is a Tsunami Warning, meaning a tsunami is imminent or occurring, requiring immediate evacuation to high ground due to potential widespread coastal flooding.
When evacuating, move quickly on foot, as traffic congestion or damaged roads may impede vehicles. Follow marked evacuation routes, which are typically indicated by a blue and white wave symbol with an arrow pointing toward safety. If moving inland or uphill is impossible due to terrain or time constraints, seek immediate refuge in a structurally reinforced building by moving to the fourth floor or higher in a vertical evacuation.
Navigating Post-Tsunami Hazards and Initial Safety
The danger from a tsunami is not over after the first wave recedes, as a tsunami is a series of waves that can arrive over many hours. Do not return to low-lying coastal areas until local authorities have issued an official “all-clear” signal, even if the water appears calm. The second or third wave may be larger than the first.
The immediate post-tsunami environment presents numerous physical hazards. Avoid walking or driving through floodwater, which may be contaminated with sewage, chemicals, and bacteria. The water can also conceal dangerous debris, such as broken glass, sharp metal, and downed power lines, which must be assumed to be energized.
Be vigilant for aftershocks if the tsunami was caused by a seismic event, as these tremors can cause further damage to weakened structures and potentially trigger additional waves. Stay away from damaged buildings, bridges, and infrastructure until they have been inspected to ensure structural integrity. Only use a phone for emergency communication, reserving the lines for essential services, and rely on battery-powered radios for official updates.