There is no specific ruling
There doesn't appear to be any specific ruling regarding Boots of Elvenkind and Tremorsense (if there was you would expect it to be mentioned in the description of the boots since this is obviously where any rules specific to how this item interacts with other rules would be).
Hence, by RAW, the boots would make no difference to Tremorsense.
Tremorsense states it enables the creature to pinpoint:
...the origin of vibrations within the specific radius, provided that the monster and the source of the vibrations are in contact with the same ground or substance.
It doesn't actually say about creatures needing to move, and it should be worth noting that the boots only state that your steps make no sound, but presumably any other sounds you make would still be transmitted through your feet to the ground (and you would, potentially, still make sounds which is why the boots only provide advantage on stealth checks to move silently rather than an automatic success).
Despite the general danger of trying to apply scientific principles to magical stuff in the world of D&D rules, which hardly ever works, there is enough ambiguity here for the DM to apply some common-sense house-rules if he/she wishes. E.g. Requiring the creature with tremorsense to make a Perception check, with advantage perhaps, rather than automatically pinpointing the location of the sneaky Boots of Elvenkind wearer.