NGA Models

These are the Attenuation Relationships developed as part of the PEER "Next Generation Attenuation" (NGA) project.

Available Models
Implementation Verification

To provide independent verification of OpenSHA's implementations of the NGA models, Kenneth Campbell (EQECAT Inc.) computed a suite of test files. These files provide mean and standard-deviation values for a sufficiently wide range of parameter settings to suggest that OpenSHA implementations are correct, or at least consistent with independent computations. The test files and README are available here (2.8 MB .zip file).

The tests include ~170,000 test calculations, the results of which all of which match to within 0.05%.

Each file has a single-line header to label the columns. The first nine columns represent values of the following parameters:

(note that not all the above are used by each NGA model)

The columns that follow represent the mean or natural-log standard deviation for various spectral periods, SA (g), plus PGA (g) and PGV (cm/s).

There are 30 separate files for testing: different NGA models, different focal mechanisms, mean versus standard deviation (sigma), whether sites are on the hanging wall, whether the event is an aftershock, and whether Vs30 is measured or inferred/estimated.