text: 1970 tonghai earthquake the 1970 tonghai earthquake occurred on 4 january with a moment magnitude of 7 . 1 and a maximum mercalli intensity of x ( extreme ) . the strike - slip rupture originated on the red river fault , which had not experienced an earthquake above magnitude 7 since 1700 , and affected tonghai county , yunnan province , china . at least 10 , 000 people were killed , making it one of the deadliest in its decade . the tremor caused between us $ 5 to $ 25 million in damage , felt over an area of 8 , 781 km2 ( 3 , 390 sq mi ) . in hanoi , north vietnam , almost 483 km ( 300 mi ) 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 . background and tectonics yunnan , the epicentral region , is one of the more seismically active chinese provinces . the earliest earthquake recorded there was in the 9th century ; however , moderate to strong ones have been observed since the 15th century . since the 9th century , 32 earthquakes with a magnitude of 7 or greater have occurred in the province . shallow strike - slip faulting is a characteristic of yunnan quakes . earthquakes in southwestern yunnan , such as the 1970 tonghai event , are less frequent than in other parts of the province . the red river fault , the fault line on which this quake is alleged to have occurred , has lacked seismological activity as a whole . red river generally rise at high angles , as shown in a 1962 ministry of geology report . marking in sedimentary rocks indicate that several large earthquakes formed on the fault during the pleistocene and holocene epochs . until this quake , no earthquake above magnitude 7 . 0 on the richter scale had occurred on this fault since about 1700 , and the fault was believed to be " dead " . 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 . damage and casualties the epicenter of the quake was about 121 km ( 75 mi ) southwest of kunming and 97 km ( 60 mi ) northwest of ; this area was mainly a tobacco - growing region . effects of the rupture were felt over an area of 8 , 781 km2 ( 3 , 390 sq mi ) . in hanoi , north vietnam , almost 483 km ( 300 mi ) from the epicenter , victims left their homes as the rupture rumbled through the city . the earthquake measured 7 . 1 on the moment magnitude scale . it may have killed more than 15 , 000 people , making it the third deadliest in china during the 20th century , and injured an additional 26 , 783 . the tremor caused between us $ 5 to $ 25 million in damage . a reuters news report , the only one in the immediate aftermath , mentioned the recording of a " severe " quake by hong kong 's royal observatory and cited an unconfirmed report that it might have destroyed part of kunming . it caused 50 km ( 31 mi ) of visible surface faulting on the tonghai fault . there was a maximum horizontal offset of 2 . 5 m ( 8 ft ) and vertical offset of about 0 . 5 m ( 1 . 5 ft ) . as a result of inversion techniques , scientists were able to decide that several events comprised the surface faulting . this further confirmed that the earthquake , along with a later earthquake in yunnan in 1973 , corresponded to a fault within the area . aftermath scientific study the earthquake was among the first to be studied over a long term by the chinese government . more than 40 chinese seismologists , engineers , and geologists visited the disaster zone to conduct research into the cause and damage of the earthquake ; some spending as much as a year collecting soil samples and recording other primary research evidence for future study . such data was collected over a broad area of almost 1400 towns within the area . reaction according to the reuters report , the survivors came together to " fight against the disaster " . much of the aid provided to survivors was in " spiritual " form . the chinese government sent tens of thousands 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 . however , the amount of aid and finances distributed was described by the beijing morning post 30 years later as " pathetically small . " the details of the earthquake were not widely publicized by chinese authorities until about 18 years after its occurrence . in china 's first decades of communist rule , its policy was to not disclose natural disasters or accidents unless foreigners were injured . while the chinese official press had not released a comprehensive report , reuters and the royal hong kong observatory both released information soon after the disaster . at the time of the quake , the xinhua news agency briefly mentioned a smaller magnitude quake but did not provide information on damage or casualties . on 19 november 1988 , nearly nineteen years later , chen 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 . he did not give a reason why his government had not previously disclosed this knowledge . government officials from china released a different estimate in 2000 , putting the death toll at 15 , 621 . china published the estimate after a memorial service for survivors and relatives was held in yuxi on january 5 . 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 . twenty - five years after the earthquake , the largest earthquake - monitoring network nationally was established in yunnan . it set up earthquake offices in every county to prepare for another large rupture . the 1970 tonghai earthquake was cited as one of the reasons behind creating the monitoring system .