try adopting wider boundaries

Check the degrees of freedom and the initial conditions.

see

https://www.researchgate.net/.../282997310_Common_Mistakes_on_...

Actually plaxis scaled up the deformation in geometry , so it seems like displacment is high.

You need to adopt the deformation scale to the real scale because the PLAXIS result by default could amplified the scale from 5 to 20 times.

Thanks for answers. The value of deformation is too high regardless of deformed mesh scale.

Widening of boundaries has been tried and results don't change.

Try to adjust the number of steps and substeps according to the phase of the seismic signal (delta T) . While

Delta T = max steps / sub steps

You can modify it in the phase explorer mode

Did you solve your problem ? I have same big horizontal displacements in my model.

Does it solve?

https://communities.bentley.com/products/geotech-analysis/w/plaxis-soilvision-wiki/45911/how-to-prescribe-a-dynamic-displacement