1622 North Guyuan Earthquake
The 1622 North Guyuan earthquake struck Ningxia, China on 25 October with a magnitude of 7.0 and a maximum Mercalli intensity scale, Mercalli intensity of X (''Extreme''). It was the only recorded big earthquake in western China for 148 years, between 1561 and 1709. The earthquake occurred on the "rake of the Zhongwei-Tongxin fault", with a mid-seismogenic depth of about . See also *List of earthquakes in China *List of historical earthquakes References

Earthquakes in Ningxia 1620s earthquakes 1622 natural disasters 1622 in China Disasters in Ming dynasty {{Asia-earthquake-stub ...
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Peak Ground Acceleration
Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an wikt:accelerogram, accelerogram at a site during a particular earthquake. Earthquake shaking generally occurs in all three directions. Therefore, PGA is often split into the horizontal and vertical components. Horizontal PGAs are generally larger than those in the vertical direction but this is not always true, especially close to large earthquakes. PGA is an important parameter (also known as an intensity measure) for earthquake engineering, The design basis earthquake ground motion (DBEGM) is often defined in terms of PGA. Unlike the Richter magnitude scale, Richter and Moment magnitude scale, moment magnitude scales, it is not a measure of the total seismic scales#Magnitude and intensity, energy (magnitude, or size) of an earthquake, but rather of how hard the earth shake ...
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