QuakeSeries is an array-like data type which contains a single time series, and associated metadata like peak values and units. All data contained by this type is generally closely related to a single physical quantity or measurement. An example of a file format which parses to this type is the PEER NGA .AT2 file.
QuakeComponent is a collection of QuakeSeries types which generally represents time series data (e.g. acceleration, velocity, displacement) which were collected in a single direction. An example of a file format that parses into this type is the CSMIP Volume 2 (.V2) spec.
QuakeMotion is a collection of QuakeComponent types which all pertain to a single shared spacial location. The data contained by this type is generally free of any spacial variation.
QuakeCollection is a collection of QuakeMotion types, often corresponding to a single site. An example of a file format that parses into this type is the CSMIP processed archive (.zip).