Significant back-to-back earthquakes in northern British Columbia (B.C.) ‘very likely’ caused by fracking: federal expert. 4.6 and 4.7 magnitude quakes northwest of Fort St. John recorded within four days, just a kilometre apart.

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UTC time 2011-08-23 17:51:04
ISC event 17331323

Local date August 23, 2011, Local time 1:51:04 pm EDT
Magnitude 5.8 Mw, Depth 6 km (4 mi)
Epicenter 37°56′10″N 77°55′59″W
Type Dip-slip (reverse)
Areas affected Canada, United States
Max. intensity VIII (Severe)
Peak acceleration 0.26 g

Casualties Several injured. On August 23, 2011, a magnitude 5.8 earthquake hit the Piedmont region of the U.S. state of Virginia at 1:51:04 p.m. EDT. The epicenter, in Louisa County, was 38 mi (61 km) northwest of Richmond and 5 mi (8 km) south-southwest of the town of Mineral. It was an intraplate earthquake with a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. Several aftershocks, ranging up to 4.5 Mw in magnitude, occurred after the main tremor.

The quake was felt across more than a dozen U.S. states and in several Canadian provinces, and was felt by more people than any other quake in U.S. history. No deaths and only minor injuries were reported. Minor and moderate damage to buildings was widespread and was estimated by one risk-modeling company at $200 million to $300 million, of which about $100 million was insured.

The earthquake prompted research that revealed that the farthest landslide from the epicenter was 150 miles (240 km), by far the greatest landslide distance recorded from any other earthquake of similar magnitude.

Previous studies of worldwide earthquakes indicated that landslides occurred no farther than 36 miles (58 km) from the epicenter of a magnitude 5.8 earthquake. The Virginia earthquake study suggested that the added information about East Coast earthquakes may prompt a revision of equations that predict ground shaking.