There are a number of references for describing site amplification factors like "Estimates of Site-Dependent Response Spectra for Design (Methodology and Justification)" by Roger D. Borcherdt. 

Here is a link to the pdf file:

http://www.ce.memphis.edu/7137/PDFs/Kappa/Borcherdt_1994_Spectra.pdf?origin=publication_detail

There are a number of references for describing site amplification factors like "Estimates of Site-Dependent Response Spectra for Design (Methodology and Justification)" by Roger D. Borcherdt. 

Here is a link to the pdf file:

http://www.ce.memphis.edu/7137/PDFs/Kappa/Borcherdt_1994_Spectra.pdf?origin=publication_detail

Firstly, you should collect some information about the site (e.g., Surface geology, Shear-wave velocity in the top 30 meters; Vs30 , Horizontal to vertical spectral ratio, or the site class based on some well-known classification like NEHRP)

Given the Vs30, you can use the equation 7 of the Borcherdt (1994) (above-mentioned paper) in order to calculate site amplification factors for different ranges of ground acceleration.

The table 3 of our paper is a case in point:

https://www.researchgate.net/publication/257137274_Real-Time_Mapping_of_PGA_Distribution_in_Tehran_Using_TRRNet_and_peeqMap

Article Real-time mapping of PGA distribution in tehran using TRRNet...

Dear Amir,

In the equation 7 of the Borcherdt (1994), how to get the value of the exponents ma and mv ?

Best Regards,

Linh

Dear Linh,

As described in the paper, ma and mv values could be obtained by equation 2c and 2d or table 2 of the Borcherdt (1994). The short-period (high frequency) factors should be used for PGA amplification, and the mid-period factors for PGV.

Dear Amir,

Yes, but ma and mv relate to Fa(vSC-IV,I) and Fv(vSC-IV,I). How to get these Fa(vSC-IV,I) and Fv(vSC-IV,I) values?

Best Regards,

Linh