An earthquake occurred in Tonghai, Yunnan province, China at 01:00:41 local time on 5 January 1970 with a moment magnitude of 7.1 and a maximum Mercalli intensity of X (Extreme).

In Hanoi, North Vietnam, almost 483 km (300 mi) from the epicenter, victims left their homes as the rupture rumbled through the city.

[4] Much of the aid provided to survivors was in "spiritual" form,[4] including Mao Zedong badges and condolence letters.

[5] Red River temblors generally rise at high angles, as shown in a 1962 Ministry of Geology report.

Since the 1970 Tonghai rupture, it is believed that the Red River fault is instead experiencing a long seismic gap similar to that of the Japan Median Tectonic Line, on which no major temblor has formed since 700 but produced massive ones during the Holocene epoch.

[4] In Hanoi, North Vietnam, almost 483 km (300 mi) from the epicenter, victims left their homes as the rupture rumbled through the city.

[4] The Chinese government sent tens of thousands of Quotations from Chairman Mao Zedong books and badges in his honor to victims as part of the relief effort, and survivors also received 14,350 sympathy letters.

[4] In China's first decades of Communist rule, its policy was to not disclose natural disasters or accidents unless foreigners were injured.

[10] On 19 November 1988, nearly 19 years later, Chen Zhangli of the State Seismology Bureau, speaking at a news conference for another earthquake that had recently occurred, estimated the death toll of the 1970 quake to be 10,000.

[4] A Yuxi Seismology Bureau official noted that the information had been classified for "political reasons" and the death toll estimate had been known among bureaucrats as early as 1997.