select
  cartodb_id,
  'minor' as type,
  ST_Buffer(the_geom::geography, 100000)::geometry) AS the_geom,
  ST_Transform(ST_Buffer(the_geom::geography, 100000)::geometry, 3857) AS the_geom_webmercator
from 
  all_day
where
  mag <= 2.9

UNION ALL 

select
  cartodb_id,
  'light' as type,
  ST_Buffer(the_geom::geography, 100000)::geometry) AS the_geom,
  ST_Transform(ST_Buffer(the_geom::geography, 300000)::geometry, 3857) AS the_geom_webmercator
from 
  all_day
where
  mag > 2.9 and mag <= 3.9

UNION ALL 

select
  cartodb_id,
  'moderate' as type,
  ST_Buffer(the_geom::geography, 100000)::geometry) AS the_geom,
  ST_Transform(ST_Buffer(the_geom::geography, 500000)::geometry, 3857) AS the_geom_webmercator
from 
  all_day
where
  mag > 3.9 and mag <= 4.9

UNION ALL 

select
  cartodb_id,
  'strong' as type,
  ST_Buffer(the_geom::geography, 100000)::geometry) AS the_geom,
  ST_Transform(ST_Buffer(the_geom::geography, 700000)::geometry, 3857) AS the_geom_webmercator
from 
  all_day
where
  mag > 4.9