Ground Motion Models

Ground motion models (GMMs) forecast the range of ground motions that may be observed conditioned on the occurrence of various earthquakes. Internally, every earthquake in a HazardModel is parameterized as a GMM_Input, for which ground motions can be calculated.

Ground Motion Model File Structure

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<GroundMotionModels>
  <ModelSet maxDistance="150.0">
    <Model id="BA_08" weight="0.3333"/>
    <Model id="CB_08" weight="0.3333"/>
    <Model id="CY_08" weight="0.3334"/>
  </ModelSet>
</GroundMotionModels>

Ground motion model files also provide limited support for additional epistemic uncertainty on ground motion (example) and will likley support uncertainty on ground motion sigma with the anticipated implementation of NGA-East. The format for these uncertainty models is subject to change at any point in the future.

A second distance cutoff is also supported (example). The models specified at the greater distance must be a subset of the near-distance models, but may have different weights. This feature may be removed in future updates.

The weights in any set of ground motion models need not sum to 1.0, but this may be enforced in the future.

Next: USGS Models