  People use Online Social Media to make sense of crisis events. A pandemic
crisis like the Covid-19 outbreak is a complex event, involving many aspects of
the social lives on many temporal scales. Focusing on the Spanish
Twittersphere, we characterize users activity behaviour across the different
phases of the Covid-19 first wave. By performing stepwise segmented regression
analysis and Bayesian switchpoint analysis on a sample of Spanish Twittersphere
users timeline, we observe that generic Spanish Twitter users and journalists
experience an abrupt positive relative increment of their tweeting activity
between March the 9th and the 14th, in coincidence with control measures being
announced by regional and State level authorities. On the contrary, politicians
follow a completely endogenous dynamic determined by institutional agenda.
