THE 7.8 magnitude earthquake in Turkiye and Syria, which has claimed over 23,000 lives so far, is producing wider geological implications that may have long term consequences, with flooding and landslips being the most immediate ones.

According to a Guardian report, subsidence has caused flooding, while hillsides are at risk of landslip, which means roads may need to be rerouted and people re-housed.

The US National Oceanic and Atmospheric Administration defines subsidence as sinking of the ground because of underground material movement, which can be caused by natural events such as earthquakes.

Significant subsidence has occurred in the coastal city of skenderun (Turkiye), which has resulted in flooding, while many hillsides around the country are at a serious risk of landslip. Roads and pipelines may have to be rerouted and people rehomed if the problem increases.

It was also reported that the sea had encroached 200 metres inland in the city, but the actual cause of the subsidence is not yet known.

Sea encroachment seen in coastal city of Iskenderun, satellite imagery reveals landslip in areas north of Gaziantep

“Although this very large earthquake produced mostly horizontal movement, it’s certainly plausible that there was a fault splay that caused some widespread subsidence like this,” Tim Wright, from the Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics in the UK, told Guardian.

Prof Bruce Malamud, professor of Natural and Environmental Hazards at King’s College London, told the Science Media Centre “hazard relief agencies and managers will also be conscious of other natural hazards and multi-hazard cascades.”

In his view, the seismic activity could trigger hundreds, if not thousands, of landslides in the days after the earthquake and subsequent aftershocks.

“Hazard managers will also be faced with the relocation of large numbers of people, and they will need to be aware of where they move these people, not moving them into another hazard-prone area, such as to floods, he said.

Similar changes were also seen in the Turkish town of Gölcük after the 1999 zmit/Kocaeli earthquake, and along the coast following the 2016 Kaikoura earthquake in New Zealand – both of which were also large strike-slip (horizontal movement) earthquakes.

Cloudy weather prevented gathering satellite imagery immediately after the quake, but clearer skies on subsequent days revealed a numbers of landslides and rockfalls across the region.

A map produced by the United States Geological Survey suggested that extensive landslip was likely to have occurred in the hilly region north of Gaziantep, which could affect tens of thousands of people.

“Based upon this we are likely to see some landslide fatalities plus substantial numbers of roads blocked by failures. This will impede the rescue work, especially … in more remote areas,” Dave Petley, an analyst of landslide events, was quoted saying.

Sokagin Sesi Gazetesi, a Turkish media outlet, tweeted a video on Feb 7 showing a landslip on the road between Adana and Gaziantep. This has raised fears regarding rural upland communities, which could be completely devastated by the landslides triggered by the massive earthquake.

Published in Dawn, February 11th, 2023