Area seismic sources are often defined where specific fault data are not known, but seismicity does exist. Area sources assume that the rate of occurrence is uniform throughout. Therefore, every location within the area has equal probability that an event will occur.

EZ-FRISK™ lets you work with one or more area seismic source databases.

To define an area source, you need the following information:

• Trace of region using latitude and longitude coordinates<
• Activity rate for region at the minimum magnitude (no. per year)
• Beta (recurrence slope)
• Minimum magnitude
• Maximum magnitude
• Minimum and maximum depth of seismicity (km)
• Probability of activity
• Coefficients for the rupture length equation
  log(rupture length) = a + b * Magnitude + sigma

The magnitude recurrence rate for all area sources is assumed to be exponential.

EZ-FRISK™ also has a variable-seismicity background seismic source database. With these seismic sources, the seismicity is assigned at discrete locations having random-rupture orientation. This model is used by the USGS for representing background seismicity. We provide the 2002 USGS background data sets.

You can easily include area and background sources in your seismic hazard analyses from one or more regions. We give you tools to conveniently select all sources in a region, to select all sources in a region within a specified distance, or to individually select seismic sources.