|A map showing the location of the December 16,|
1920 M 7.8 earthquake
From Wiki here
The epicenter appears to have been Dingxi City. Dingxi is a "prefecture level city" in the southeast of Gansu province. It's area covers 20,300 sq. km, and the population is reported as 2.7 million people (in 1 urban district, 6 counties, and 119 towns). It was an important city in early development of some of China's cultures because the Wei River, one of the Yellow River's biggest tributaries, flows here. The surrounding terrain hills and ravines cut into the loess deposits, weak sandy deposits, possibly water-saturated from the recent rains. This does not bode well for damage.
The earthquake occurred near midnight UTC on July 21. This follows, by only 8 days, a major landslide that reportedly trapped at least 100 tourists after a landslide cut off a road during a week of storms that have flooded rivers and triggered mudslides. At least 86 people were reported to have died by Chinese state media. Mudslides and floods are common in the mountainous areas of China, but this year seems to have been an especially bad one in many areas of Asia.
|Map showing the relation of todays earthquake to|
the major city of Tianshui.
Gansu is also a region with many earthquakes. In 1879, an earthquake with an estimated magnitude of 8.0 and Mercalli intensity XI (extreme) killed an estimated 220,000 people. This earthquake was preceded by foreshocks for a few days. The earthquake also triggered landslides that dammed local rivers up to 40-120 m.
Today's earthquake appears to be followed by numerous aftershocks, though it is difficult to tell where they are relative to the initial location given as 13 km east of Chabu. Some are reported at a distance of 156 km from Tianshui in Gansu province, a city of 3.5 million people.
Here is a site that is updating and comparing locations of today's quake, and that also gives earthquake locations since 1900 in this region.