What you need to know about tsunami impacts on the Hawaiʻi islands

HONOLULU (KHON2) — You’ve seen the new signs that have popped up all the islands indicating whether you are entering or leaving a tsunami hazard area.

But how much do you really know about tsunamis and how they can impact life here in the islands.

KHON2.com was able to catch up with Dr. Charles “Chip” McCreerey who is the Director Pacific Tsunami Warning Center located at Pearl Harbor.

He explained more about these powerful waves, how tsunamis work and what would happen to us and our islands if a tsunami made it across the Pacific.

Dr. McCreerey’s journey to tsunami science

Dr. Charles McCreerey’s journey to becoming a leading expert in tsunami science was anything but typical.

“I moved to Hawaiʻi when I was 17 because my older brother was a geophysicist at the University of Hawaiʻi,” Dr. McCreerey explained.

He began his college years pursuing an undergraduate degree in fine arts and printmaking. However, his interest in geophysics never waned.

“I worked at the Hawaiʻi Institute of Geophysics while completing my degree,” he said. “Eventually, I went back to school and earned a Ph.D. in geophysics.” His passion for the subject led him to the Pacific Tsunami Warning Center in 1993, where he has been ever since.

The basics of tsunamis

Tsunamis are often misunderstood, but Dr. Charles McCreerey provides a clear explanation of their nature and behavior.

“Tsunamis are waves caused by underwater disturbances, such as earthquakes, volcanic eruptions, or landslides,” he explained. These disturbances displace a significant volume of water, generating waves that propagate across the ocean.

Distinction from regular ocean waves

Unlike typical ocean waves, which are driven by wind and affect only the surface layer of water, tsunamis involve the entire water column—from the surface to the seabed.

This fundamental difference is what gives tsunamis their unique characteristics. Dr. McCreerey noted, “Regular ocean waves are surface phenomena, while tsunamis penetrate the entire depth of the ocean, which allows them to carry much more energy.”

Behavior in different depths

In the deep ocean, tsunamis travel at incredible speeds, reaching up to 500 to 600 miles per hour.

“In deep water, the wavelength of a tsunami can be very long, and the wave height is relatively small,” Dr. McCreerey said. “This allows them to move rapidly across vast distances with minimal disruption.”

However, as tsunamis approach shallower coastal areas, their behavior changes dramatically.

“When tsunamis reach shallower depths near the shore, their speed decreases significantly,” Dr. McCreerey explained. “As the water becomes shallower, the tsunami’s energy is compressed into a smaller volume of water, causing the wave height to increase.” This phenomenon is known as “wave shoaling.”

The compression of energy leads to a dramatic increase in wave height, which can result in towering waves that can cause significant destruction upon reaching the shore.

“The increase in height and the slowing down of the wave are directly related to the decreasing depth of the water,” Dr. McCreerey added.

Tsunamis are distinct from regular ocean waves due to their ability to affect the entire water column and their dramatic changes in behavior as they approach shorelines.

Understanding these basics helps clarify why tsunamis can be so devastating and underscores the importance of early warning systems and effective preparedness measures.

Local vs. distant tsunamis

Hawaiʻi faces two primary types of tsunami threats: local and distant. Understanding the differences between these can help in preparing for and responding to their impacts.

Local tsunamis

Local tsunamis originate from earthquakes within the Hawaiian Islands, often associated with volcanic activity.

“Our active volcanoes can generate local tsunamis,” Dr. Charles McCreerey explained.

These tsunamis are typically triggered by seismic activity related to volcanic eruptions or movements of the Earth’s crust within the islands. Local tsunamis generally have a shorter travel distance to the coast, which means they can strike more quickly.

Dr. McCreerey emphasized that while these tsunamis are less frequent, they are closely tied to the geological features and volcanic activity within Hawaiʻi itself.

Distant tsunamis

Distant tsunamis, on the other hand, originate from earthquakes occurring far from Hawaiʻi, particularly from regions around the Pacific Ring of Fire—a zone of high seismic activity encircling the Pacific Ocean.

“The most concerning are those from the Aleutian Islands,” Dr. McCreerey noted. These tsunamis can traverse the vast expanse of the Pacific Ocean and reach Hawaiʻi in approximately 4 to 4.5 hours.

The Pacific Ring of Fire is home to several active fault lines and volcanic zones, making it a significant source of distant tsunami threats. Dr. McCreerey also mentioned other potential sources, such as Chile and Japan.

“Tsunamis can come from as far away as Chile or Japan,” he said. “In these cases, we generally have more time to prepare—about 7 to 8 hours from Japan and around 14 hours from Chile.”

This additional time for distant tsunamis allows for more comprehensive warning and preparation efforts.

It also underscores the importance of having effective monitoring systems in place to detect and assess the severity of incoming tsunamis, regardless of their origin.

While local tsunamis pose an immediate threat due to their shorter travel time, distant tsunamis provide a longer window for preparation.

Understanding these distinctions helps in crafting effective response plans and ensuring that communities are ready to act swiftly when needed.

How tsunamis impact Hawai ʻ i

The impact of a tsunami on Hawaiʻi can vary widely depending on where the tsunami originates and the specific characteristics of local geography.

Understanding these variations is key to grasping why some areas may experience more significant effects than others.

“Tsunamis can affect different areas in different ways,” Dr. Charles McCreerey explained. “For instance, if a tsunami originates from the north, it tends to produce larger waves along the North Shore.”

This is because the direction from which a tsunami comes can influence which parts of the coast receive the most intense waves. The orientation and shape of the coastline play a significant role in determining the tsunami’s impact.

Certain locations are particularly susceptible to heightened tsunami effects due to their geographical features.

“Hilo Bay and Kahului Bay are prime examples of this,” Dr. McCreerey noted. “These bays are known for their resonating effects. When tsunami waves enter these bays, they can get amplified, leading to higher wave heights and increased potential for damage.”

The resonance phenomenon occurs because the shape and depth of these bays can cause the tsunami waves to bounce back and forth, building up in height as they do so.

“The wave energy becomes trapped and focused within the bay, which can lead to more severe flooding and damage,” Dr. McCreerey said. “This effect can make these areas particularly vulnerable during a tsunami event.”

Dr. McCreerey also highlighted how these effects were evident during the 2011 Japan tsunami.

“For example, places like Hanauma Bay had to be closed for several days after the tsunami,” he explained. “Even as the initial tsunami waves waned, the water continued to push inland and cause problems due to the way the waves had sloshed around in the bay.”

This prolonged effect illustrates how tsunami waves can keep impacting a location long after the main surge has passed.

“The waves don’t just stop immediately,” Dr. McCreerey noted. “In some cases, the water continues to move and cause disturbances for days, making it necessary to keep certain areas closed for safety.”

Understanding these regional impacts emphasizes the importance of localized preparedness and response strategies.

By recognizing the specific risks associated with their geography, communities can better prepare for and mitigate the effects of tsunamis.

The science behind tsunami waves

Understanding how tsunami waves behave is crucial for effective preparation and response. According to Dr. McCreerey, tsunamis are complex phenomena that differ significantly from regular ocean waves.

“In the open ocean, a tsunami’s height might be less than a meter,” Dr. McCreerey explained. “These waves are often not noticeable to ships at sea because their height is so minimal. The real danger starts when they approach the coast.”

One key feature of tsunami waves is their long wavelength, which allows them to wrap around islands and affect coastlines from various directions. This characteristic can make their impact more widespread and unpredictable.

As a tsunami travels from the deep ocean to the shore, its behavior changes dramatically. “When tsunamis approach shallow water near the coast, their speed decreases significantly,” Dr. McCreerey noted. “In the open ocean, these waves can move at speeds of up to 500 to 600 miles per hour, similar to a commercial jet. But as they reach the shore, they slow down to about 20 to 30 miles per hour.”

This reduction in speed has a profound effect on the wave’s height. “The energy of the tsunami is compressed as the wave travels into shallower waters,” Dr. McCreerey said. “The wave height increases, not because the tsunami gains more energy, but because the energy is concentrated into a smaller volume of water.”

This process causes the water level to rise significantly and stay high for a longer period, allowing the tsunami to push further inland than typical surf waves. Regular surf waves have short wavelengths and arrive in quick succession, causing them to recede rapidly. In contrast, tsunami waves have long wavelengths and their effects can last for minutes or even hours.

“Tsunamis can flood areas far beyond the reach of normal surf,” Dr. McCreerey added. “Because these waves arrive over a longer period, they can keep the water level elevated for a prolonged time, which is why they can cause such extensive damage.”

The way tsunamis interact with coastlines also varies. “The waves wrap around islands and can impact both sides of a coast, which is different from how surf waves behave,” Dr. McCreerey explained. “If a tsunami originates from the north, the north shore will typically experience larger waves, but the south shore will also be affected.”

Certain coastal features, like bays and inlets, can amplify the tsunami’s impact. “In some locations, such as Hilo Bay and Kahului Bay, the waves can resonate and build up more dramatically,” Dr. McCreerey said. “This is similar to pushing a swing—you add a little more energy with each push, and it results in a larger swing. Bays can amplify the tsunami waves in a similar manner.”

Understanding these scientific principles helps in preparing for tsunamis and developing effective evacuation plans. The Pacific Tsunami Warning Center continuously monitors for large earthquakes and potential tsunamis, aiming to provide early warnings to help mitigate the impacts of these powerful waves.

The challenge of predicting tsunamis

Predicting the exact impact of a tsunami is a complex and challenging task. The behavior of tsunami waves as they travel across the ocean and interact with coastlines is influenced by a variety of factors, making precise predictions difficult.

“The wave pattern can be quite complicated,” Dr. Charles McCreerey explained. “Tsunami waves do not travel in a simple, linear fashion. As they approach shore, they can reflect off and wrap around islands, causing the water to slosh back and forth in unpredictable ways.”

This reflection and wrapping effect occurs because tsunami waves have long wavelengths, which allows them to bend around obstacles such as islands.

“Unlike regular surf waves that are more straightforward and predictable, tsunami waves interact with the geography of the coastline and islands, leading to complex wave patterns,” Dr. McCreerey said. “The waves can bounce between islands and wrap around them, which can significantly alter their impact.”

The difficulty in predicting the exact impact is compounded by these interactions.

“When a tsunami arrives at a coast, the waves can create multiple reflections and complex patterns that can continue to oscillate for an extended period,” Dr. McCreerey noted. “For instance, during the 2011 Japan tsunami, the water kept moving back and forth in some bays for days after the initial wave arrived.”

These prolonged effects occur because the waves, once reflected or trapped in bays, can maintain their energy and continue to cause disturbances long after the first wave has passed.

“In places like Panama Bay, for example, the water kept sloshing back and forth even after the main tsunami waves had arrived,” Dr. McCreerey explained. “This continued motion made it dangerous for people to enter the water for several days.”

The variability in tsunami wave behavior means that while warning systems and models can provide estimates and alerts, the exact effects on any given location can still be difficult to predict with precision.

“Our models and warnings are based on the best available data, but the actual impact can vary due to these complex interactions,” Dr. McCreerey said. “We strive to give the most accurate information possible, but the nature of tsunamis means there are always uncertainties.”

Understanding these challenges highlights the importance of preparedness and timely response. Communities at risk from tsunamis must be ready for potential variations in the tsunami’s impact and follow evacuation and safety protocols to protect themselves during these unpredictable events.

Lessons from past tsunamis

The 2011 Japan tsunami is a stark reminder of the immense power and unpredictability of tsunami waves. This event highlighted critical lessons about the scale of damage that tsunamis can inflict, even in regions with advanced preparedness.

Unexpected magnitude and impact

Dr. Charles McCreerey described the 2011 Japan tsunami as a particularly instructive case.

“The magnitude of the earthquake was unexpected,” he said. “The tsunami was larger than anticipated and overwhelmed protective measures like seawalls.”

The earthquake that triggered the tsunami was a magnitude 9.0, far exceeding what most experts had expected for that region.

The resulting waves were so powerful that they breached existing seawalls and flood defenses, illustrating that even the most robust protections can be insufficient against extreme events.

The importance of preparedness

Japan’s experience underscores a crucial lesson about tsunami preparedness.

“Even in well-prepared countries like Japan, the sheer size of the tsunami can exceed defenses,” Dr. McCreerey explained.

Despite Japan’s extensive efforts to build seawalls and implement evacuation plans, the tsunami’s magnitude and impact were so severe that they surpassed these defenses.

This situation serves as a powerful reminder that no amount of preparation can guarantee complete safety from such colossal forces.

Dr. McCreerey emphasized that this event demonstrates the importance of continuous preparation and adaptation.

“It’s a lesson in why ongoing preparation and understanding are essential,” he said. The 2011 disaster revealed the need for regular updates to safety protocols, improved infrastructure, and public education about the risks and responses to tsunamis.

Learning and adapting

The aftermath of the 2011 tsunami led to significant changes in tsunami preparedness and response strategies worldwide.

Dr. McCreerey highlighted that the global community has since focused on enhancing early warning systems, refining evacuation plans, and educating people about the behavior of tsunamis.

The goal is to better prepare for future events and minimize the loss of life and property damage.

The 2011 Japan tsunami has provided invaluable lessons about the limits of current defenses and the need for relentless vigilance and improvement in tsunami preparedness.

Understanding and adapting to these lessons are vital for protecting communities against the devastating potential of future tsunamis.

Preparing for tsunamis

Hawaiʻi takes a proactive approach to preparing for potential tsunamis, with a focus on ensuring that residents and visitors can respond swiftly and effectively in the event of a tsunami warning.

Local preparation efforts

Dr. Charles McCreerey emphasized that Hawaiʻi’s preparedness strategies are robust and multifaceted.

“We have evacuation plans and warning systems in place,” he said. “The goal is to get people to safety as quickly as possible.”

These efforts include regularly updated evacuation routes, public education campaigns, and community drills designed to familiarize residents with emergency procedures.

The state also maintains a network of sirens and alert systems to provide timely warnings when a tsunami threat is detected.

Global initiatives

In addition to local measures, there is a significant global effort aimed at enhancing tsunami preparedness worldwide.

Dr. McCreerey highlighted the United Nations Decade of Ocean Science for Sustainable Development, a global initiative focused on improving coastal community readiness.

“This program aims to make every coastal community tsunami-ready,” he explained. “This involves having designated evacuation areas, regular drills, and reliable warning systems.”

The Decade of Ocean Science initiative promotes the development of comprehensive tsunami preparedness plans, including the establishment of clearly marked evacuation routes and safe zones.

Regular drills and public education campaigns are also integral components, designed to ensure that people know what to do when a tsunami warning is issued.

Community involvement

Dr. McCreerey also pointed out the importance of community involvement in tsunami preparedness.

“It’s crucial for local communities to be actively engaged in preparation efforts,” he said. This includes participating in drills, staying informed about tsunami risks and understanding the specific evacuation procedures for their area.

Community engagement helps to ensure that everyone knows how to respond effectively, which can significantly enhance overall safety and resilience in the face of a tsunami threat.

Hawaiʻi’s proactive stance on tsunami preparedness, supported by global initiatives like the United Nations Decade of Ocean Science, aims to ensure that residents are well-prepared and equipped to handle the challenges posed by tsunamis.

Through a combination of local and global efforts, the goal is to enhance readiness, improve response times, and ultimately reduce the impact of these powerful natural events.

Looking ahead

While tsunamis are rare, their potential impact makes preparation vital.

“In Hawaiʻi, we may see a few tsunami warnings in our lifetimes,” Dr. McCreerey said. “It’s important to take these warnings seriously and act quickly.”

The scientific understanding of tsunamis continues to evolve, helping to improve preparedness and response.

“Tsunamis are a fascinating and complex phenomenon,” Dr. McCreerey concluded. “Our goal is to ensure that we can provide accurate warnings and keep people safe when these events occur.”

To find out more about tsunami’s, you can click here. You can watch Dr. McCreerey’s full interview in the video above.

By learning from experts like Dr. McCreerey and staying informed, we can better prepare for the possibility of a tsunami and protect our communities.