- To define a small number of discrete crustal regions (with associated attenuation parameter values) to capture essential differences in distance attenuation that affect ground motions.
- To develop rules for computing ground motions when paths cross regions.
The Path/Source WG will evaluate the CENA data to identify regions that have significant differences in the ground motion attenuation (e.g., regions that require different GMPEs). Following the preliminary definition of regions, appropriate values of Q, geometrical spreading and duration for each of the regions will be defined. An additional sub-task involves the selection of representative 1D crustal velocity structure for each of the regions.
The TI team will make the final decision on the number of separate regions considering the trade-off between simplicity (fewer regions) and the accuracy of GMPEs that most affect the hazard at CENA sites.
Another sub-task involves the development of a set of rules for the treatment of region boundary crossings (source in one region and ground motion estimates in another).