How to isolate turntable from footstep shake or vibration

Even while the Oracle turnable that I use has a built-in springs suspension by design there is a low or even sub-low frequency boom every time someone walks in a room. This becomes really bad with the subwoofer’s volume set high as the low frequency footsteps make straight to subwoofer where they are amplified shaking everything around. It seems the cartridge is picking up the footsteps very efficiently as even a lightest foot down becomes audioable. What can be done to attempt to isolate the turntable from the low frequency vibrations? Interesting, that the lower the volume of the subwoofer, the less the footstep shake is evident and with the subwoofer turned off it is a barely a problem at all. 
@cleeds , you obviously have no experience with powerful subwoofers and turntables ...
You’re half-right - I don’t use powerful subwoofers. I use a full-range speaker system that is essentially flat in-room to below 20 hZ.
The problem is not the turntable. It could not be happier. The problem is the subwoofers trying to reproduce every little irregularity on the record causing the woofers to make long excursions. If I turn the volume up loud enough I can get the voice coils to hit their stops making a very painful sound.
That sure sounds like a problem to me. I want my woofers to reproduce what’s on the LP, unfiltered. If you’re getting "irregularities" that cause "long excursions," then it sounds like you have arm/cartridge resonance problems. Those can usually be resolved without relying on rumble filter Band-Aids but - as I said - rumble filters do work. It’s fine if you like them.
After checking the suspension you should try a Wall shelf made for the TT. Like this
Pro-Ject Wallmount it 1 Turntable Shelf-Audio Advisor

This helps to eliminate foot falls since it is mounted to the wall instead of sitting on the floor. Another way with suspended tables is to hang it from the ceiling. This takes some knowhow to do but is very doable if you know how to find the ceiling joists. I used this back in the 70’s & 80’s with great success..
thecarpathian, if the bridge DID collapse, we guess you be crushed and out of a home. 😄👍
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I find it amusing that you are doing exactly what you infer I am.😄 👍