Shear Strain calculation by strain tensor during Dynamic Analysis

Hi everyone. Question. What tensor is better to calculate shear strain in dynamic analysis? shear strain rate tensor or shear strain increment tensor? In 2D, fsr or fsi using the fourth component.
How can I calculate shear strain from fsi? twice exy from fsi tensor?
Thanks in advance.

Shear strain increment is the total strain (relative to the initial displacement - usually zero);
Shear strain rate is the strain increment in the current step over time step.