Abstract: It is a time-dependent map giving the probability of strong shaking at any
location in California within the next 24-hours.

Scientists with the Swiss Seismological Service and the Advanced National
Seismic System (ANSS) have collaborated to develop techniques that quantify the
increased likelihood of future earthquake shaking from earthquake clusters in
California.

In this system, the ... probability of strong earthquake shaking (with a Modified
Mercalli Intensity of VI or greater) in the next 24 hours is calculated and
updated every hour. The system considers all the earthquakes, large and small,
that are recorded by the California Integrated Seismic Network (CISN), the
California element of the Advanced National Seismic System. For each event, the
probability that it will be followed by an earthquake large enough to cause
strong shaking is calculated from the known behavior of aftershocks and the
possible shaking pattern predicted from historic patterns. These probabilities
apply both to aftershocks smaller than the first event and to the possibility
that the "aftershock" will be larger than the first event which will then
become a foreshock.