How to adjust the phase of one part of an interferogram

Recently, I was doing the D-InSAR analysis of the 2021 Maduo earthquake in Qinghai, but the combination of extremely low coherence and great deformation led to errors in the expansion. EJFielding suggests that I assume a to realize it, but I don’t know how to do it and what algorithm or principle to use. Can you tell me? thank you

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