New USGS-Adjusted subduction GMMs for Alaska

There are AK review panel concerns about over-prediction of NGA-Sub interface GMM ground motions (both global and Alaska regionalized models). We are therefore going to implement bias-corrected versions of the three that we intend to use for subduction interface:

• AG_20_GLOBAL_INTERFACE
• KBCG_20_GLOBAL_INTERFACE
• PSBAH_20_ALASKA_INTERFACE PSBAH_20_GLOBAL_INTERFACE

Tasks:

• The attached values should be put in a separate coefficients file and brought in to each GMM class (see the NGA-East adjustments as an example). Use the average of 0.01s and 0.03 s for 0.02s. Use the 1s value for PGV. Pass in the slab() flag to the constructor and set the correction to 0 if true.

• Add a akBiasCorrection() method that can be overridden in subclasses.

• The bias corrections values are log-normal and so just need to be subtracted from the final mean value conditioned the above method returning true.

• bias_nga: Interface_adj.csv

• bias_nga: Interface_adj-v2.csv

• bias_nga_new: Interface_adj_Combined_NGA_New.csv

• bias_new: Interface_adj_Post_NGA_only.csv