We don't have synonyms for richter yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are nichter, righter and richer.
(n) :
(seismology) (Followed by a decimal number): A Richter scale magnitude to indicate the severity of an earthquake. "Richter" is prefixed to the magnitude value. This has generally been superseded by the Moment-Magnitude Scale
(n) :
(seismology) (Followed by a decimal number): A Richter scale magnitude to indicate the severity of an earthquake. "Richter" is prefixed to the magnitude value. This has generally been superseded by the Moment-Magnitude Scale