Description: This is a commonly seen signal on all instruments. Something has driven the seismometer to go off-scale (sometimes a deliberate recalibration). The instrument responds slowly and then takes a minute or more to settle back down to a zero reading.
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Description: This is wind. Wind affects seismometers in two ways. Distant storms increase the size and number of large waves in the ocean. These vibrations propagate inland and can recorded as long as the storm persists, often for several days. Such vibrations are the curse of seismologists world wide. It is not surprising that many of the clearest seismograms in the world are recorded deep in the middle of large continents such as in Kazakstan. The second type of wind noise is very local. As trees blow in the wind, they move the ground around them. This can create a considerable amount of unwanted noise. For this reason, seismic stations are located in fields away from trees and other large structures whenever possible.
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Description: This is definitely electronic noise in the instrument or in the network communications. The rapid oscillations between similar values does not correspond to any real earth noise. No earth noise would come and go repeatedly as seen here. This is not an accurate representation of the ground's motion. Occasionally this happens. Lamont technicians are usually quick to fix such technical glitches if they do not go away on their own.
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Description: While these signals may look earthquake-like at first, it is highly unlikely that such massive earthquake waves would exist on their own without any other vibrations, particularly large surface waves that would shake for hours. The key to identifying noise like this is looking for repetition. If such an anomalous signal was somehow created, it is highly unlikely it would occur a minute or an hour later. Luckily, this type of artificial electronic noise often repeats itself regularly. This is a sure sign it is not a real signal.
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Description: This one is tricky. It may at first look like wind noise. It s low amplitude, relatively constant and continues for hours or days on end. The key feature here is the signal's regularity. Notice how the signal repeats itself with only slight changes from one line to the next. Earthquakes and other earth noises are not cyclic and have no knowledge of our arbitrary system of time keeping. It is highly unlike that an earthquake signal would ever repeat itself exactly our occur regularly every 5 minute for example.
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Description: The same logic used to understand the last few noise signals can be applied here. The signal is too regular in time. There are no other types of shaking associated with it. And each pulse is similar to the previous ones (note how the two red pulse are nearly identical). It is hard to say what the source of this signal is, but earthquakes or explosions can clearly be ruled out.
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Description: Though it looks completely different, this one should be clear from the examples above. It is an unwanted signal not associated with an earthquake, vibration or any other type of real vibration. Though its source is unknown, we can rule out any real vibrations because of its unlikely shape. This is certainly electronic noise in the instrument or network.
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