Social media communities have emerged recently as open and free communication platforms to support real-time information sharing among members. Drawing on social capital theories, we develop a theoretical model to investigate how the two types of social capital (bonding and bridging) contribute to the individual and collective well-being of virtual communities through information exchange. Research hypotheses were tested through survey instruments and computer archive data of 475 members of a large social network site during the Wenchuan earthquake (2008) in China. We find that bonding has a positive and significant impact on bridging. Both bonding and bridging have positive and significant impacts on information quality, but not on information quantity. Results also suggest that information quality is more critical to individuals and collective well-being than information quantity after a disaster.