shakemap.utils.generic_amp¶
- shakemap.utils.generic_amp.get_generic_amp_factors(sx, myimt)[source]¶
Returns an array of generic amplification factors the same shape as the lons and lats members of sx. The amplification factors are pulled from the grids in the operator’s configured directory: ‘<install>/data/GenericAmpFactors’. Any HDF files in that directory will be considerd amplification files and will be examined for factors that apply to the coordinates in sx. The factors are assumed to be in natural log units and will be added to the output of the GMPE (or IPE). For coordinates outside the available grids, zero will be returned. If more than one file contains amplifications for any of the coordinates (i.e., overlapping grids), then the factors will be summed together. It is the operator’s responsibility to ensure the proper behavior is observed for the selected output IMTs considering:
If ‘myimt’ is ‘PGA’ and there is no PGA grid in the HDF file, the ‘myimt’ will be set to ‘SA(0.01)’ for that file.
If ‘myimt’ is ‘PGV’ and there is no PGV grid in the HDF file, the ‘myimt’ will be set to ‘SA(1.0)’ for that file.
If ‘myimt’ is spectral acceleration (i.e., ‘SA(x)’ where ‘x’ is the period), and SA of that period is not found in the HDF file, the function will first attempt to interpolate the grids of the next lower and next greater periods found in the file. The interpolation is done as a weighted average of the grids with the weights being defined assigned by the log difference in periods. If the period of ‘myimt’ is less that the shortest period in the file, the grid for the shortest period is used. If the period of ‘myimt’ is greater that the longest period in the file, the grid for the longest period is used.
Interpolation in geographic space is nearest neighbor.
Coordinates that fall outside the grid bounds of any given file are assigned an amplification factor of zero.
- Parameters:
sx (Sites Context) – An OpenQuake sites context specifying the coordinates of interest.
myimt (str) – A string representing an OpenQuake IMT.
- Returns:
An array of generic amplification factors corresponding to the coordinates specified by sx.
- Return type:
array
