A shallow earthquake registered by the USGS as M5.7 hit off the coast of Northern California, US at 19:50 UTC on September 22, 2017. The agency is reporting a depth of 9.1 km (5.6 miles).
The epicenter was located 58 km (36 miles) W of Ferndale, 58 km WNW of Petrolia, 67 km (41.6 miles) W of Fortuna and 74 km (46 miles) WSW of Eureka, United States.
Some 1.1 million people are estimated to have felt weak shaking.
A tsunami is not expected, NTWC said.
USGS issued a green alert for shaking-related fatalities and economic losses. There is a low likelihood of casualties and damage.
Overall, the population in this region resides in structures that are resistant to earthquake shaking, though vulnerable structures exist. The predominant vulnerable building types are unreinforced brick masonry and reinforced masonry construction.
Recent earthquakes in this area have caused secondary hazards such as landslides and liquefaction that might have contributed to losses.
Estimated population exposure to earthquake shaking
Selected cities exposed
Featured image credit: USGS