Seismic Source Databases
EZ-FRISK lets you work with one or more seismic source databases.
These databases can store:
You can easily include seismic sources in your seismic hazard analyses from one or more databases and
from one or more regions of those databases.
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.
By using a database separate from your analyses, you can update custom source data in one location.
Any subsequent computations will use the new source parameters.
Consequently, you can update previous analyses by simplying recalculating
the results.
We provide you with a seismic model for your licensed region. In regions
like the USA and Canada where seismic models are publically available,
you are free to view and change all aspects of the model. Elsewhere,
Fugro USA Land has developed proprietary models. When working with
a proprietary model, you can view all aspects of the model, but you
can not copy or change sources.
To define a fault seismic source, you can specify:
- Trace coordinates (latitudes and longitudes)
- Fault mechanism (strike-slip, normal, oblique, thrust, subduction)
- Orientation (depths and dip angles to define the profile)
- Minimum magnitude
- Maximum magnitude
- Coefficients for the vertical and horizontal rupture length or rupture area equations:
log(rupture length) = a + b * Magnitude + sigma
log(rupture area) = a + b * Magnitude + sigma
- Recurrence model (mixed characteristic-exponential, pure characteristic, exponential, normal)
- Recurrence rate (slip rate, activity rate)
- Beta (change in recurrence with magnitude)
- Probability of activity
For each fault you can define multiple, weighted models of magnitude recurrence.
To define a subduction slab seismic source, you can specify:
- Upper and Lower Trace coordinates (latitudes, longitudes and depths)
- Minimum magnitude
- Maximum magnitude
- Coefficients for the vertical and horizontal rupture length or rupture area equations:
log(rupture length) = a + b * Magnitude + sigma
log(rupture area) = a + b * Magnitude + sigma
- Recurrence model (mixed characteristic-exponential, pure characteristic, exponential, normal)
- Recurrence rate (slip rate, activity rate)
- Beta (change in recurrence with magnitude)
- Probability of activity
For each fault you can define multiple, weighted models of magnitude recurrence.
To define a subduction interface seismic source, you can specify:
- Upper and Lower Trace coordinates (latitudes, longitudes and depts)
- Minimum magnitude
- Maximum magnitude
- Coefficients for the vertical and horizontal rupture length or rupture area equations:
log(rupture length) = a + b * Magnitude + sigma
log(rupture area) = a + b * Magnitude + sigma
- Recurrence model (mixed characteristic-exponential, pure characteristic, exponential, normal)
- Recurrence rate (slip rate, activity rate)
- Beta (change in recurrence with magnitude)
- Probability of activity
For each fault you can define multiple, weighted models of magnitude recurrence.
Area seismic sources, sometimes referred to as seismic zones, 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.
To define an area seismic source, or a zone, you can specify:
- Trace of region using latitude and longitude coordinates
- Activity rate for region at the minimum magnitude (no. per year)
- Beta (change in recurrence with magnitude)
- 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
- Fault mechanism
The magnitude recurrence rate for all area sources is assumed to be
exponential.
Variable seismicity gridded sources are used by the USGS and other organizations as an
alternative to seismic zonation. Given an earthquake catalog, variable seismic sources
calculate seismicity for a particular location by applying a Gaussian filter
to the historical seismicity. For computational purposes, the seismicity is assigned
to a set of grid points at even increments of latitude and longitude.
Typically, end users will not created gridded sources, but the program
has a complete interface for view and editing gridded sources.
The magnitude recurrence rate for all gridded sources is assumed to be
exponential or pure characteristic.
Clustered seismic sources are used to represent sets of faults where
the event rates of the separate sources are not independent. For example, this technique
is used in the USGS 2008 National Seismic Hazard map to model hazard from the New Madrid seismic zone.
Composite seismic sources allow grouping of multiple related seismic sources into
a single source for reporting purposes. Often it is necessary to use multiple logical
seismic sources to represent all of the logic tree branches for a single conceptual
seismic sources. A composite seismic source allows the hazard from these logical seismic sources
to be presented as a single source in reports and charts.
