The movies of earthquake motion have been constructed from a 5000
node array run by NodalSeismic Inc. for Signal Petroleum. The network
was deployed for
approximately 6 months during the first half of 2011, and
was designed to provide high resolution images of the Long Beach Oil
Field. The survey had an active component that ran 9am-4pm weekdays. The
sensors are autonomous units that run 24 hoirs a day. They
have a standard velocity sensor with a lower roll-off at 3 Hz.
The active source component of the survey consisted of Vibrator sources
runing either as a single unit or in a group of four. Each vibrator
can exert a force of 30 tons, but in normal operation the force is dialed
back to 20-30% of that because of the close proximity of buildings.
They sweep 10-80 Hz
in a chirp that lasts 20 seconds. The crosscorrelation of the the chirp
signal with the data recorded by the seismic network, simulated an
|Earthquake||Movie (click to run)||Notes|
distance 5 km
Notes: The amplitudes of the shaking at each station are displayed on a color scale with blue for negative values and red for postive values. In the first movie only negative values are shown. In the second movie, only positive values are shown. For the first two movies the filter is set from 1-50 Hz which shows both P and S waves. In the third movie, the filter is 1-14 Hz, which emphasizes the S-wave.
distance 35 km
distance 20 km
distance 75 km
distance 75 km
distance > 90.0
The energy in the Japan Earthquake is very small and is below the frequency range of the sensors, which have a response band of 3 Hz and above. The energy also arrives at Long Beach nearly vertically. Nevertheless, the waves arriving from Japan can be seen at low frequency waves that span a large part of the apperature of the network
Three successive frames of the Carson earthquake show how
the focussing of energy changes as the earthquake passes.
The maximum at each station is displayed for three earthquakes. The red values ate the maximum intensity and for the carson event represent an acceleration of about 5 cm/sec**2.