Japan has recorded a series of powerful aftershocks in the past several hours, including a magnitude 5.7 earthquake near the east coast of Honshu and a 4.9 earthquake in the Hokkaido region shortly after.

A marriage between a can of beans and a smoke alarm, 6-pound seismic sensors collect data that researchers use to establish trends.

The clusters of earthquakes have all been underneath the East Bay suburb of San Ramon, which is close to the Calaveras fault. There were at least 19 earthquakes of magnitude 2 or greater on Monday alone.

Nevada Seismological Lab says today’s widespread quake alerts were a false ShakeAlert activation. No earthquake occurred, and Nevada’s system detected no activity.