On December 26, 2004, a 9.1 magnitude earthquake off the coast of Sumatra, Indonesia, caused the generation of catastrophic tsunamis, the worst in history, as the length of the fault zone that caused the disaster was about 1,300 kilometers.
The rift dislodged the sea floor, forming subsequent waves that reached 50 meters high.
This caused an estimated $ 10 billion in material damage, and the death of about 230,000 people in 14 countries, with Indonesia, Sri Lanka, India and Thailand the most affected.
Tsunami waves caused enormous human and material losses (Getty Images)
What is the meaning of the tsunami?
A tsunami is a series of massive ocean waves caused by earthquakes, underwater landslides, and volcanic eruptions.
A tsunami can travel at speeds of up to 48 kilometers per hour, with waves that may reach tens of meters in height, and as a result of the huge amount of water and energy resulting from the movement, its effects are devastating.
In a new study - published in the journal "PNAS" on May 11th - scientists identified a new, and possibly devastating, danger of the occurrence of tsunami waves in specific regions of the world, and this danger is linked to the strike-slip fault faults) of the subsurface crust, where blocks of rocks slide along the fault line horizontally along each other.
New reasons
Until now, it was believed that earthquakes at slip faults could generate large tsunamis only if they also caused underwater landslides, but through some detailed modeling and with the help of the Blue Waters supercomputer;
Scientists have shown that the risk is much greater.
The results showed that lateral movement and energy generated when sliding faults occur can produce large tsunamis on their own, and the researchers say it is a bit like moving a glass of water from side to side.
“The physical model used in this study provides insight into the risk associated with sliding fracture specifically,” said civil engineer Mohamed Abdel-Majeed, co-researcher and professor of civil and environmental engineering, in a press release from the University of Illinois at Urbana-Champaign. We need to calculate such a risk to mitigate future damage to bays near sliding faults. "
In order for a tsunami to occur, the researchers found that the presence of what is known as an "intersonic earthquake" is important, and an intersonic earthquake means that a rift occurs very quickly so that movement along the fault is faster than the secondary waves (shear wave) generated in the crust.
Coastal cities close to faults are at risk, especially when faults cross bays (Getty Images)
The shores of the bays are in danger
Coastal cities near sliding faults are at risk, especially when faults cross bays;
Examples include the San Francisco Bay Area, the Gulf of Izmit in Turkey, and the Gulf of Aqaba in Egypt;
Which means that the edges of these bays will be subjected to pull and push.
This leads to 3 connected phases: the initial motion and shock waves, the displacement of water during the earthquake, and the movement of the resulting tsunami wave, and each phase can evolve differently depending on local conditions.
Civil engineer Ahmed Al-Banna - the study's lead researcher and professor of civil and environmental engineering from the University of Illinois at Urbana-Champaign - said, "Each of these stages will have a different impact depending on the geography of the surrounding land and the depth of the bay. Unlike earthquakes and the subsequent displacement of water that occurs on Many miles offshore, the earthquake and tsunami occurring within the narrow confines of the bay allow little time for warning. "
Attempts to predict
The aim of this study is to understand more about how tsunamis are formed and which parts of the planet are most at risk, so that we are better prepared for future events;
Before now, this risk was not considered in the models.
Previously, the relationship between slip faults and tsunamis was studied, but only in specific geographical areas, but now researchers have examined the basic factors for these types of faults.
This will enable them to locate different places around the world that would be subject to this scenario.
Researchers believe that the tsunami that struck Palu on the Indonesian island of Sulawesi in September 2018, which was triggered by a magnitude 7.5 earthquake, was caused by the mechanism described in this study.
Describing the 2018 tsunami in Indonesia, civil engineer Costas Sinolakis - an associate professor in the study and professor of civil and environmental engineering at the University of Southern California - said describing the 2018 tsunami in Indonesia, "It looked like a bulldozer entered and flattened the city, which is why it is so important to try." Understand what really happened. "