Hi Mark. The timing depends upon the size of the quake and the distance from the sensors. In the SJB area the time ranges from about 8 to 20 hours before the quake.

The thing to look for is the build up of the stress; it will then level off for a very short period then drop. The quake will occur anywhere from 8 to 20 hrs after the drop.

The one thing that was learned very early on is that the time it takes the strain to build then drop is not a good indicator of the magnitude of the impending quake. No one knows why, or at the very least no one has said why.

A “A” level alert indicates a strong quake is expected. Take Care…Don in creepy town.