Earthquakes that a seismograph records as having a force of 2.5-4 are felt as mild tremors. They cause little or no damage, although trees may sway and windows rattle.
Earthquakes are the vibrations caused by rocks breaking under stress against an underground surface called a fault plane while a tremor is an involuntary movement of earth surface caused by stress in the underground rocks. They are both signs of seismic movement within the earth.
The rumblings being investigated belong to the tectonic tremor, a less hazardous form of seismic activity that occurs far deeper into the earth’s core than the devastating earthquakes that occur much closer to the earth’s surface.
One major difference between tectonic tremor and earthquakes is that tectonic tremor causes relatively weak ground shaking and is not cause for immediate concern.
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