A friendly Sorcerer with Careful Spell could help you achieve this effect
There is no general rule that exempts casters from making saving throws for their own spells and, if a specific spell had such a rule, it would state it overtly.
However, Sorcerers can choose to take this useful metamagic ability:
When you cast a spell that forces other creatures to make a saving throw, you can protect some of those creatures from the spell’s full force. To do so, you spend 1 sorcery point and choose a number of those creatures up to your Charisma modifier (minimum of one creature). A chosen creature automatically succeeds on its saving throw against the spell.
A Sorcerer could use Careful Spell to allow you to automatically succeed on a saving throw, from a spell they cast, and not fall prone.
The Earthquake spell has a number of ongoing effects; Careful Spell would not protect you from these effects on subsequent turns after it was initially cast.
They could, however, also use Careful Spell to protect you from other similiarly impressive spells (ie. Fireball etc.), many of which have no ongoing effects.
However, Careful Spell cannot protect the caster
The rules text says quite specifically that you can protect 'some of those' [...] 'other creatures'. 'Other creatures' cannot mean you.
To achieve this effect, you'd therefore need a friendly sorcerer to cast a spell on you using Careful Spell; you wouldn't be able to use Careful Spell to protect yourself.
Evocation wizards have a similar ability
At level 2 School of Evocation wizards gain access to the feature Sculpt Spells. This works in a very similar way to Careful Spell for sorcerers but is limited to affecting evocation spells. Earthquake is an evocation spell, as are many other impressive spells, without the ongoing effects that Earthquake has.
However, this solution is less optimal than Careful Spell for your exact scenario, as Earthquake is not on the Wizard spell list (it's on the list for Clerics, Druids and Sorcerers), though lots of other evocation spells are. To cast Earthquake a wizard would therefore need to be multi-classed.