However, in general, these works use supervised learning frameworks (Popescu et al., 2011;Ritter et al., 2012), and/or they use either a coarse representation of events, which reduces to topic modeling or classification of entire tweets (Popescu et al., 2011;Becker et al., 2011;Ritter et al., 2012), or a simplified representation of events with few arguments (Sakaki et al., 2010;Popescu et al., 2011;Benson et al., 2011;Ritter et al., 2012).
for example, for a particular earthquake, the USGS reports a depth of 22 km., while NOAA reports 25 km 2 .