Earthquake Engineering

SeismoSignal" Software is very good for your purpose,
You can learn it easily

Check out the QuakeManager software for selecting and scaling optimal suites of ground motion records given a number of criteria and constraints.

Apart from the mesh refinement, you should apply the load in many subsets. As the dynamic load suddenly applied in few subsets (time intervals) distorts the elements highly. You can do this either by reducing the time increment or by increasing the number of subsets to solve the problem.

You can do this either by reducing the time increment or by increasing the number of subsets to solve the problem.