The "big 19" basic explanation – Snorlax (week: 11-1) – Earthquake isn't all that bad
If we only look at the STAB and type effectivenesses, Earthquake is arguably superior to Hyper Beam. Body Slam is still the best since it comes frequently and is a legacy move, while being hard to be dodged by attackers with a charge move with 1 bar.
Earthquake protects Rock and Steel weaknesses, and also Gengar, the best ghost Pokémon in the current meta. Gengar is ghost, thus taking approximately 61.2% damage from normal attacks counting STAB. However, due to its poison, it takes 140% damage from ground attacks. Earthquake is almostly equally as easy to dodge as Hyper Beam.
HB base power:
1500.511.2=91.8
Earthquake base power:
120*1.4=164
The formula itself isn't very accurate, since there are other functions in the damage formula.
How to counter Earthquake Snorlaxes?
Lick + Earthquake:
Exeggutor seems to be a good choice, but Murkrow saves you more potions, which has flying (resisting Earthquake) and dark resists Lick, making up for its bad defense stat. Still probably not enough, 2 undodged Earthquakes equal to the faint of your Murkrow.
ZH + Earthquake:
Murkrow shines here, too. Both moves deal 51% damage to it. Exeggutor will be a long-term plan if you are facing multiple ones, also resisting both moves by 28.6%. 2 Solar Beams might be enough to kill the Snorlax if yours is at a quite high level.
Happy birthday, Pokémon GO. Niantic, how/where is the anniversary event in the game master code?
GoDex, why is Lick dealing 5 damage to a same level Murkrow, but 1 for Zen Headbutt? Immunity in Pokémon GO does not mean a 0 multiplier.
Answers
I'd rather use a Skarmory over a Murkrow against Snorlax.
The only thing that Snorlax can have that Skarmory doesn't resist is Lick... and Lick isn't scary. Even against an Earthquake Snorlax, Skarmory has a bit more HP and literally triple the defense that Murkrow has.
Edit: Also no sane person is going to use Gengar against Snorlax. Snorlax resists Shadow Claw, and is guaranteed to have SE quick move damage, and might have SE charge move damage.
fun fact... resisted Shadow Claw still does more DPS than Sucker Punch, though SP's energy generation might make up for that.
Also... you're still throwing a fairly squishy pokemon against the second tankiest pokemon in the game that is guaranteed to have SE damage and might not even have one of the moves your mon double resists. How does that sound like a good idea?