There are two ways to determine the events per second for a Cisco MARS SIEM system.
See the current EPS the system is processing
You can see the real time EPS the system is currently handling by looking in the logs. This is found under Admin > System Maintenance > View Log Files.
Once there, expand the time frame and search for something that looks like this:
total avg rate is the current EPS the system is processing.
Calculate it based on events per month
On the Summary screen there is a table on the top left side that says how many events have been received. You can change this to month and then divide the value by the number of seconds in a month.
In my case I see there are
1,137,479,506 events for the last 30 days. I divide this by
2,592,000 which is how many seconds are in 30 days. This leaves me with