Why am I getting extra PEEQ along with the slip surface?

Hi, 

I am trying to simulate landslide induced by strength reduction method where the soil is medium dense sand. but i am getting extra plastic strain (PEEQ) at the bottom along with the slip surface. I am using dynamic explicit analysis and using Mohr Coulomb Plastic Model. How can I remove this extra PEEQ? What could be the reason?

 

Edu ABAQUS