how can an earthquake cause a tsunami

How can an earthquake cause a tsunami?

A range of geophysical events, such as volcanic eruptions, landslides, and meteor strikes, can trigger tsunamis.

Tsunamis are massive, catastrophic ocean waves and they can be devastating.

While many events can lead to tsunamis, underwater earthquakes are one of the most frequent and significant drivers of tsunamis.

And that is why many people are truly interested in knowing, “how an earthquake can cause a tsunami?

An earthquake causes a tsunami through tectonic plate movement and subduction as well as displacement of the ocean floor. 

How Can an Earthquake Cause a Tsunami?

As mentioned already, an earthquake is probably the biggest risk factor for having a full-blown tsunami attack, but what causes it in the first place?

Here are possible explanations of how earthquakes can cause tsunamis: 

Tectonic Plate Movement and Subduction

tectonic plate movement and subduction

The movement and sinking of tectonic plates are one of many factors in the formation of tsunamis.

Stress builds up around the edges of the tectonic plates as they continuously move, especially in subduction zones

Strong earthquakes can result from the release of pent-up stress, which in turn can cause the displacement of large volumes of water, leading to tsunamis.

Tsunamis are generated when the earthquake causes a quick vertical displacement of the ocean floor, which in turn drives shockwaves through the water column.

Tsunamis pose a particularly serious threat to coastal communities located near subduction zones.

It is because these zones are often extremely close to the epicenter of large underwater earthquakes. 

Displacement of the Ocean Floor

displacement of the ocean floor

Tsunamis are caused in large part by the movement of the ocean floor caused by an earthquake.

Sudden movements of the tectonic plates along a subduction zone can result in significant elevation or subsidence of the ocean floor.

Because of this movement, the volume of water immediately above it also moves.

This causes a sequence of waves to propagate away from the initial point of disruption. These waves may be difficult to detect in the broad ocean. 

But, as they approach the coast, they acquire height and intensity, eventually becoming the enormous, catastrophic waves characteristic of tsunamis. 

Propagation of the Tsunami Wave

propagation of the tsunami wave

To learn the connection between earthquakes and tsunamis, you have to understand how the waves spread.

When the seabed shifts due to an earthquake, waves travel outward in all directions from the epicenter.

Tsunami waves have tremendous force and can travel great distances quickly.

Incoming waves slow down when they approach shallow coastal locations, transferring their kinetic energy to a more noticeable rise in wave height. 

The resulting wall of water can be several stories high and crash against the coast, causing widespread flooding and destruction.

It is crucial to have a firm grasp of how tsunami waves travel and how they behave in various marine and coastal ecosystems. 

It is important to accurately estimate their potential repercussions and develop efficient preparedness and warning systems.

Fact: Tsunami waves travel fast and are capable of covering a vast distance at speeds higher than 500 mph. 

Factors Affecting Tsunami Size and Impact

factors affecting tsunami size and impact

It is clear that earthquakes can cause tsunamis, but certain factors play a role in determining the devastating effects of a tsunami.

For instance: 

Magnitude and Depth of the Earthquake

The magnitude and depth of an earthquake are the primary factors in determining the size and impact of a tsunami.

Large, shallow earthquakes are more likely to move large amounts of ocean bottom, leading to larger tsunamis.

Tsunamis are possible with any earthquake of magnitude 7.0 or above, with the largest events typically happening in conjunction with earthquakes of magnitude 9.0 or higher. 

Distance from the Epicenter

distance from the epicenter

Another factor that might affect the magnitude and severity of a tsunami is its distance from the earthquake’s epicenter to the coastline.

Larger, more damaging waves are possible for the coastal areas closest to the epicenter. 

In contrast, when the tsunami energy diminishes along the shore, smaller and less destructive waves may hit areas further from the source. 


One of the most important factors in determining the magnitude and severity of a tsunami is the coastline and ocean floor’s shape.

Tsunami waves can vary in height and impact along a coastline due to topographical features such as:

factors such as topography
  • Troughs
  • Undersea ridges
  • Coastal embayment
Fact: The local geography can concentrate the tsunami's energy in some locations, resulting in far higher wave heights and more widespread destruction. 

Warning Signs of Earthquake Causing Tsunami

Among the most destructive natural disasters, tsunamis caused by earthquakes pose a serious risk to coastal communities all over the world.

Potentially saving the lives of thousands, early detection of the warning signs connected with these occurrences can allow for evacuation and the deployment of safety measures. 

warning signs of earthquake causing tsunami

Let’s talk about some of the many warning indicators that suggest the possibility of an earthquake creating a tsunami. 

How Deep is the Earthquake Focus?

The possibility for a tsunami to form depends in large part on how deep the epicenter of the earthquake is.

Tsunamis are more likely to occur after shallow-focus earthquakes (those with hypocenters at or below 70 km), which can displace large volumes of water.

On the other hand, a deep earthquake might not shake the ocean floor enough to cause a significant tsunami. 

Ground Shaking

ground shaking

Tsunami warning signs include intense and persistent ground shaking during an earthquake, especially in coastal locations.

The shaking may be a precursor to a tsunami since it indicates the release of a lot of energy and the movement of the ocean floor.

It is a good idea to evacuate as soon as possible especially if you are close to coastal areas. 

Rapid Sea Level Changes

Rapid and obvious fluctuations in water level near the coast may occur in the minutes before a tsunami strikes.

Extreme fluctuations in sea level can either reveal the ocean floor at low tide or inundate terrain that is usually dry at high tide.

Two of the most obvious signals that the water level is changing include drawdown and run-up.

And they can also be telltale signs that a tsunami is in the making. 

Unusual Ocean Behavior

unusual ocean behavior

Several anomalous ocean phenomena tell you a lot about an impending tsunami.

Some of them include:

  • Strong currents
  • Whirlpools
  • Shifts in water temperature or color

You need to bear in mind that tsunami waves may be approaching if the earthquake triggers the movement of significant amounts of water

Consequences of Earthquake-Generated Tsunamis

consequences of earthquake-generated tsunamis

Okay, so you know earthquakes are behind tsunamis, but how damaging can they be?

Well, they can definitely cause serious damage in so many ways.

For instance: 

Loss of Life

Significant human casualties are a possible outcome of a tsunami caused by an earthquake.

Strong waves can carry people away, trap them behind falling objects, or cause them to drown as the water floods the land.

Reducing casualties from tsunamis requires both rapid evacuation and public understanding of threats.

Fact: Tsunamis can be devastating, with the 2004 Indian Ocean tsunami killing an estimated 230,000 people in 14 countries. 

Damage to Infrastructure

damage to infrastructure

Widespread destruction of coastal and inland infrastructure is possible by tsunami waves.

Powerful flood waters can wipe out entire neighborhoods by washing away homes, businesses, and transportation links.

It might take years, even decades, to recover from the costs of repairing or rebuilding such facilities. 

Disruption of Essential Services

Tsunamis can cause the widespread failure of life-sustaining utilities, such as:

  • Power plants
  • Water distribution systems
  • Communication networks

This disturbance can make it harder for emergency workers to do their jobs, slow down the distribution of relief, and add insult to injury for the populations in need. 

Environmental Damage

environmental damage

Earthquakes can trigger tsunamis, which can have devastating effects on the environment in addition to human life and property. 

Those high waves can have a bad impact on coastal ecosystems, such as :

  • Mangroves
  • Coral reefs
  • Wetlands

With saltwater seeming into freshwater systems, there could be a severe shortage of drinking water.  

Fact: Debris and dangerous materials can spill during tsunamis and pollute land and water, causing threats to humans and wildlife alike. 


How can an earthquake cause a tsunami?

Knowing the geological processes that lead to a tsunami is crucial for preparing for and reducing the effects of natural disasters.

An earthquake can cause a tsunami simply through the movement of tectonic plates and the shifting of the ocean floor.

The intensity of an earthquake has an impact on the likelihood of having a tsunami.

It is important to pay attention to warning signs to lower damage caused by earthquake-induced tsunamis.