The 1970 Tonghai earthquake occurred on 4 January 1970 in Tonghai, China. The rupture originated on the local Yunnan Province’s Red River fault, which had not experienced an earthquake above magnitude 7 since 1700. The earthquake had a magnitude of 7.7 and killed at least 15,000 people, making it one of the deadliest in the history of China. The tremor caused between US$5 to $25 million in damage, felt over an area of 8,781 km (5,456 miles). In Hanoi, North Vietnam, almost 483 km (300 miles) from the epicenter, victims left their homes as the rupture rumbled through the city.
Occurring during the height of the Cultural Revolution, it was not widely publicized by the Chinese government for well over a decade. The amount of aid and finances distributed was described by the Beijing Morning Post as "pathetically small". Much of the aid provided to survivors was in "spiritual" form, including Mao Zedong badges and condolence letters. Nevertheless, the earthquake was among the first to be studied over a long term by the Chinese government. It was cited as one of the reasons behind creating the largest earthquake monitoring system in China, 25 years later.