The wall section is located between structures 17 and 18. Measurements are typical based on measurements at various locations along the wall. ["Unraveling the Mongolian Arc: a Field Survey and Spatial Investigation of a Previously Unexplored Wall System in Eastern Mongolia" by Ying Tung Fung, Angaragdulguun Gantumur, Ido Wachtel, Amartuvshin Chunag, Zhidong Zhang, Or Fenigstein, Dan Golan and Gideon Shelach-Lavi, 27 December 2023, Journal of Field Archaeology.]Credit: Authors
I am thinking it caused by Graboids.
See the Tremors documentary for more information.