half hours after the initial shock, at 7:17, at the southern end of Tangshan fault, near Ninghe ("C" on the map in the section below), with a magnitude of 6.2 . Another significant aftershock () occurred in November near Ninghe. Most aftershocks occurred between these end points, in a zone 140 km long and about 50 km wide. Many buildings were further damaged by the aftershocks. The aftershock zone remains seismically active in the twenty-first century. Earthquakes measuring 4.5 to 4.7 occurred in 2012, 2016 and 2019. On 12 July 2020, a 5.1 strike-slip earthquake struck the northern part of the Tangshan Fault. It produced its own sequence of aftershocks that ended on 17 July 2020. The earthquake only caused minor damage to buildings in Tangshan. Its occurrence stirred a debate among scientists into whether the recent earthquakes are aftershocks of the 1976 event or are background seismicity. Damage The damage done by an earthquake depends primarily on two factors. First, the intensity of shaking, which depends mainly on the magnitude of the earthquake rupture, the distance from the epicenter, and the nature of the local soil and topography, with soft soils (e.g., sediments and fill) more likely to amplify the intensity and duration of the shaking. Second, the design and construction of the structures being shaken, with houses built of adobe or stone, wooden houses without a well-built frame, and unreinforced masonry construction being especially vulnerable. The seismic risk had been greatly underestimated and almost all buildings and structures were designed and built without seismic considerations. As a result, Tangshan was "mainly a city of unreinforced brick buildings", sitting right on top of a major fault line. The power (magnitude) of the Tangshan earthquake is indicated by the extent of where it was felt: up to away, across most of northeastern China, and even in Mongolia and Korea. In and around Beijing, from the epicenter, the shaking reached an intensity of VI on the Chinese intensity scale (similar to the Modified Mercalli Intensity Scale), with nearly 10% of all buildings damaged, and at least 50 fatalities. The economic loss totaled to 10 billion yuan. Intensity XI and X zone The rupture occurred under the southern part of the city, and propagated northeastward on a fault that runs through the middle of the city. The maximum intensity was "XI" (eleven) on the 12-degree Chinese scale. Nearly every building and structure