The first quakes registered magnitudes of 2.5 and 3.0 within a short period of time early on Halloween morning, awakening residents in some neighborhoods of Fort Worth, Irving, Euless and Grand Prairie.
Seismologists said that had the shaking not occurred in the middle of the night, people probably wouldn’t have noticed it.
Several more tremors occurred during the remainder of Friday and on Saturday in the same general area between Fort Worth and Dallas.
The last earthquake to hit the North Texas area was a 3.7 magnitude tremor in the Greenville area, east of Dallas, in 1997.
There are no significant faults or seismic features that could produce a major earthquake in the region, and the U.S. Geological Survey believes the recent swarm could be due to temperature changes or the “settling” of the ground.
Geoscience professor John Ferguson of the University of Texas at Dallas told the Dallas Morning News that the area gets small quakes about every 10 years, but such a swarm has never before occurred beneath the Dallas-Fort Worth area within recorded history.
The most powerful earthquake ever recorded in Texas occurred in 1931 near the Big Bend town of Valentine. It registered a magnitude of 6.0, destroying a school and damaging chimneys, walls and frame structures, according to reports published at that time.