Just been two smaller ones off cali coast I believe, a 5 and a
6. The depth where the earthquake begins to rupture. This depth
may be relative to mean sea-level or the average elevation of
the seismic stations which provided arrival-time data for the
earthquake location. The choice of reference depth is dependent
on the method used to locate the earthquake. Sometimes when
depth is poorly constrained by available seismic data, the
location program will set the depth at a fixed value. For
example, 33 km is often used as a default depth for earthquakes
determined to be shallow, but whose depth is not satisfactorily
determined by the data, whereas default depths of 5 or 10 km are
often used in mid-continental areas and on mid-ocean ridges
since earthquakes in these areas are usually shallower than 33
km.