Noise or Quake?

Can you tell the difference between earthquake and noise? Our sensors record all sorts of noise. They record background noise from computer fans, sharp spikes from jackhammers or doors slamming, lurches from laptops being moved, and more. They also record electrical noise due to small fluctuations in the current from the USB cable. But sometimes earthquake signals are observed. Compare the noise and earthquakes below.

Noise: Table Bumped Earthquake: Dec 11 2011 Mexico M6.7
Noise: Electrical Noise & Cable Taps Earthquake: December 14 2011 Japan M4.9
Noise: Electrical Noise & Dropped Weights Earthquake: December 23 2011 New Zealand M4.3
Noise: Electrical Noise & Step Near Sensor Earthquake: January 23 2012 Chile M5.8