[9] Yunnan is a mountainous region lying east of Tibet, and north of the Red River Fault that strikes southeast along the Red River into North Vietnam and the South China Sea.

The Red River fault is deep – some believe it may reach the lithosphere[10] – and forms a major tectonic boundary that separates Indochina from the South China block.

[12] This has uplifted the Tibetan Plateau (and the Himalaya Mountains) and forced it eastwards, pushing the South China Block and Indochina towards the westward subducting Philippine Sea plate and creating various extensional structures.

[13] All of this has created a complicated geological structure with many faults, which in western Yunnan has allowed heat and fluids from the subducting Indian plate to rise into the upper crust, creating the Tengchong volcanic field to the north of Longling and the Longling fault (location of the first event), and west of the Nu River and Nu River fault (location of the second event).

[14] It appears that igneous intrusions have weakened the bedrock in this area, which has led to uneven accumulations of stress, which caused the earthquake.