What low-cut filter (high Pass frequency) to be used for the response spectrum (Tripartite plots)? I am currently working on differentiating between hard/soft site responses in Indo-Gangetic Plains and the Himalayas and using a high-pass frequency of say 0.2 Hz, is suppressing displacement responses in the displacement sensitive region of Tripartite plots? Should I be using any low-cut filter in such cases? And what about a high-cut filter (currently using 40 Hz)? if so, what should be the range?

Below attached is one station response spectrum corrected at different low-cut filters and the suppression in the long-period spectrum can be well seen. Please help on the same.

Thank you so much