I had a friend whose summer job, a long long time ago, was to travel around an unsuspecting rural area, lay a heavy steel plate on the ground, and whack the plate with a sledge hammer. Apparently he also had some kind of seismometer or accelerometer nearby. This was apparently a cheap and dirty way to get some idea of the soil and rock below the surface.
This was on Earth, not Mars.
The question InSight and active pinging of Mars asks about generating artificial seismic events on Mars for InSight's seismometers to listen to. @DrSheldon's answer mentions that this is not part of the plan; that InSight is expected to return meaningful data without this.
It doesn't mean that it wouldn't benefit from it though.
What kinds of schemes might a frugal and/or clever space agency use to generate seismic events that would be meaningful and useful for InSight measurements of Mars?
I can imagine two classes, one to help verify nothing is wrong, so something local perhaps, and the other far enough away to give geological or even planetary information.