And now that they've identified those signals they'll be able to look back at decades of data and use these newly discovered seismic fingerprints to better identify small earthquakes like this in the past.
This permits scientists to accurately map their observations no matter the weather or time of day and to cover large areas far more quickly than before.
Xu Yeqian, a mother of four from the southern Guangdong province, told Sixth Tone that schools had previously offered cooking and other courses voluntarily.