1. A computer-implemented method for analyzing microseismic data from a subterranean zone, the method comprising: receiving microseismic event data associated with a fracture treatment of a subterranean zone; identifying coplanar subsets of microseismic events in the received microseismic event data, each of the coplanar subsets comprising a non-collinear triplet of microseismic events in the received microseismic event data; determining a basic plane orientation for each of a plurality of basic planes defined by the coplanar subsets, each basic plane orientation being defined by the non-collinear triplet of microseismic events in a respective one of the coplanar subsets, each basic plane having an orientation relative to a common axis; identifying, by data processing apparatus, clusters of orientations of the basic planes adaptively based on an extent of variation in the orientations; identifying the number of orientations associated with each of the clusters; displaying a histogram of the basic plane orientations, wherein the histogram indicates the number of orientations associated with each of the clusters; generating a fracture plane for the each of the clusters based on microseismic events associated with the each of the clusters; and displaying the fracture plane to show time evolution of the fracture plane that represents a physical fracture within the subterranean zone.