Focal sphere
= Focal sphere
An imagined <sphere> around a seismic point source on which source-to-station ray takeoff directions are plotted. A lower-hemisphere equal-area projection commonly displays first-motion polarities and nodal planes.
= Focal sphere
An imagined <sphere> around a seismic point source on which source-to-station ray takeoff directions are plotted. A lower-hemisphere equal-area projection commonly displays first-motion polarities and nodal planes.