MyShake

There are plenty of professional services that offer detailed information about the seismic activity of given areas. However, this app from the University of Berkeley provides this information by collecting data directly from devices with this app installed.

The app uses your device's gyroscope to measure vibrations and detect earthquakes in real time. To validate the accuracy of the measurements, the app collects all the data from a given area and compares it. If the data matches in the majority of cases, it's considered valid.

This app is great for two reasons: on one hand, you can use it to stay updated on seismic activity; and on the other, you can help collect data to calculate the magnitude of earthquakes on the Richter scale.