- Sandbox: Construct Earthquake Scenarios and Conduct Ground Motion Analysis
- User Based Global Earthquake Scenario Page
The following briefly discusses conducting ground motion analysis for a user-defined earthquake scenario. This page is reached after a user registers a fault database with the program and defines an earthquake scenario using a combination of the registered segments. The GM analysis program and the page are designed to conduct ground motion for sites defined along a line connecting markers A and B for user-defined shallow soil conditions, see Figure 1.
A critical component of any earthquake GM analysis is the formulation of the empirical equations (GMPEs) used to represent the states of the earthquake source and regional wave propagation, see earthquake source function and propagation of earthquake ground motions for details. The GM module here is designed to allow maximum flexibility for evaluating the impacts of different rupture states and regional wave propagation environments on ground motions at sites of interest.
The effects of different tectonic environments on earthquakes GMs are accommodated by a logic-tree type formulation of the GM. Users can simulate different seismotectonic environments by defining weighting factors for the two GM prediction equations (GMPEs) branches. One GMPE branch represents active-tectonic environments, consisting of four GMPEs as recommended by the USGS for the western US. The other GMPE branch represents stable tectonic environments, composed of seventeen GMPEs as recommended by the USGS for the eastern US.
The ground motion parameters analyzed are the peak ground acceleration, PGA, and 0.2s and 1.0s spectral parameters. The ground motion plot shows the median and \(\pm\) one standard deviation.
Figure 1. An example of two hypothetical fault segments near Tabas, Iran. Two different weighting factors for active and stable GMPEs are used to demonstrate the impacts. It should be noted that faults and GMPEs’ weighting factors are only for demonstration and do not reflect reality.