On February 6, 2023, devastating earthquakes occurred in the area of the Turkish-Syrian border. Researchers have now analyzed which tectonic processes were responsible for the catastrophe. They were on site just one day after the quake and recorded the surface faults. Combined with seismic data, they were able to reconstruct how the quake spread and why it became so strong. The results provide new insights into how earthquakes occur and can also contribute to better protective measures.
In the early morning hours of February 6, 2023, the earth shook near the Turkish-Syrian border. With a magnitude of 7.8, it was one of the strongest quakes in the region since records began. Another earthquake with a magnitude of 7.5 followed around nine hours later. The quakes caused widespread destruction in southeastern Turkey and northern Syria. More than 59,000 people died and over 125,000 were injured. Property damage is estimated at more than $100 billion.
Photographs taken the day after the quake
A research team led by Jiannan Meng from the Chinese University of Geosciences in Wuhan was on site in the disaster area one day after the quake. Even before the tracks were changed by further aftershocks, the team took photos of the faults using drones and their own explorations on the ground. Some of these show directly how the earth's plates have shifted relative to one another. A previously straight path suddenly breaks off and continues a few meters further to the left. New ditches have formed and deep furrows run through the ground.
“Our rapid on-site deployment made it possible to obtain high-quality ground and aerial images of the surface deformations that were only so easily visible for a short period of time,” the team writes. “Together with corresponding seismic data, these images provide insight into the processes by which tectonic plates interact within two large-scale continental transform systems.”
Devastating plate movements
In the area of the Anatolian city of Kahramanmaraş, where the earthquake was strongest, three tectonic plates meet: the Arabian, the Anatolian and the African. “In terms of plate tectonics, the course of the earthquake can be described in simple terms as the Arabian plate making a sudden move to the north, whereupon the Anatolian plate responded by moving to the west,” explain the researchers.
Unlike most other earthquakes documented to date, Meng and his team's observations indicate that the largest ground deformations are not located where the quake's epicenter was. Instead, the rupture sequence began slowly at the boundary between the African and Arabian plates. 24 seconds later it hit the border with the Anatolian Plate. “There was the highest energy release and a maximum displacement of 6.7 meters,” reports the team. “The explosive impacts are likely due to stresses accumulating in this part of the Eastern Anatolian Fault Zone over several hundred years.
Basis for better protective measures
The results show how the sudden displacement of one plate can cause an adjacent plate to react to that movement, multiplying the effects. According to the researchers, the second violent earthquake nine hours later also occurred in response to the changes in tension in the ground. “Our observations could ultimately help protect populations in other potentially vulnerable regions on the plate boundary by incorporating them into building regulations and preparedness exercises,” say the researchers.
Source: Jiannan Meng (China University of Geosciences, Wuhan) et al., Science, doi: 10.1126/science.adj3770