Via the USGS:
The Earthquake Notification Service (ENS) is a free service that sends you automated notification emails when earthquakes happen in your area.
(Example of an ENS notification email)
New accounts default to receiving notifications about earthquakes with magnitude 6.0 or greater however you can customize ENS to only deliver messages for certain areas, at specified times, and to multiple addresses. ENS can even send text notifications to your cell phone.
Click HERE to go to the site and subscribe.