Unconventional production of oil or gas (or geothermal heat) requires increased permeability of the reservoir. This is achieved by high pressure injection which fractures the formation at the reservoir. 

This process induces microseismicity or, in some cases, induced seismicity, i.e. felt earthquakes. Microseismic monitoring serves as a tool for mapping stimulated reservoir and/or preventing induced seismicity. 

For more information here a link to wikipedia.