Deadly Tsunamis

October 1, 2018
By Jessica Duke, MD

Tsunamis are one of the deadliest natural disasters in human history. In the past 20 years alone, tsunamis have claimed over 250,000 lives. The majority of those deaths came in 2004 after a 9.1-magnitude earthquake in the Indian Ocean triggered a tsunami that killed an estimated 230,000 people. On September 28, 2018, a 7.5-magnitude earthquake off the coast of Indonesia generated a towering 20-foot tsunami that washed over the Indonesian island of Sulawesi. This tsunami claimed nearly 2,000 lives and displaced another 70,000 people. Unfortunately, with climate change and global warming, the frequency and magnitude of these devastating events will undoubtedly increase.


What is a tsunami?

Tsunamis are a series of waves caused by the displacement of a large volume of water, most commonly from an earthquake. Compared to normal offshore ocean waves, tsunami waves have a small amplitude (wave height) and long wavelength. These waves lose speed and gain height as they approach coastal areas in a process called shoaling. By the time tsunami waves reach the shore, they can reach heights of 100 feet and speeds of 20-30 miles per hour. These waves not only cause damage as they flood an area on their way inland, but also as the water drains off with large amounts of debris. Tsunami waves may continue to arrive over a period of hours, with significant time between the wave crests. 


What to do in the event of a tsunami?

If you live near or travel to a coastal area, be aware of your tsunami risk. Make sure to listen to emergency information and know your evacuation route. Be alert to signs of a potential tsunami, such as an earthquake or unusual ocean behavior (sudden rise or draining of water). If there is an earthquake in the area, drop to your hands and knees, cover your head and neck with your arms, and hold on to any sturdy furniture. Once the earthquake subsides, if there are any natural signs or official warnings of a tsunami, get to high ground as far inland as possible. If you are in a boat, face the direction of the waves and go out to sea. If you are in the water, grab onto something that floats, such as a raft or wood.


In the immediate setting, the smashing tsunami waves put victims at risk for both submersion and traumatic injuries. If you find yourself caught in the water, protect your airway by grabbing onto something buoyant and swim to safety. If you encounter a drowning victim, first ensure the scene is safe before attempting rescue. If possible, reach or throw, don’t go into the floodwater, as even just a few inches of moving water can sweep you away. Furthermore, the water may contain dangerous debris and fallen power lines. Once the victim is safely out of the water, perform the primary survey in the airway-breathing-circulation sequence, as the primary problem in drowning is respiratory arrest. If the victim is not breathing, administer 2-5 rescue breaths. If there is no response following rescue breaths, CPR should be initiated in a 30:2 ratio of chest compressions to rescue breaths until vital signs are re-established, the rescuers are unable to continue, or advanced life support is available.


In the days to weeks following a tsunami, survivors risk dehydration, malnutrition, infection, and worsening of chronic medical problems because of the disruption in transportation, power, communications, and food and water supply. Having emergency supplies prepared for this type of event can prevent these types of issues. In rare cases, the ocean-dwelling bacterium Vibrio vulnificus can cause necrotizing wound infections if injured skin is exposed to contaminated water. These patients require prompt antibiotics and surgical evaluation.