This seismogram is a recording of the 1994 Northridge
earthquake from station CMB of the Berkeley Digital 
Seismic Network.  The record displays 24 hours of data, 
beginning approximately 8 hours before the mainshock.
The Mw 6.7 event was immediately followed by magnitude 
5.9 aftershock, which is lost in the arrivals from the 
main event. Aftershocks are visible at 15:07 (Ml 4.2), 
20:46 (Ml 4.9), and 23:33 (Ml 5.6). 

This figure is provided by the Berkeley Seismological Laboratory.