Hi Romain, 

Sharp-wave ripples are described as "random" high-frequency events mostly occurring during the slow-wave stage of sleep. According to several studies in rats, they can present an averaged frequency of occurrence of ~0.2Hz, however, as they are random events this number can vary due to several factors, such as amount of REM/slow-wave sleep, amount of sleep/activity, etc.

Hope this helps.

Best,

Claudio