A 4 . 6 - magnitude earthquake rattled Northern California overnight Thursday , shaking residents from San Francisco to north of Sacramento .
shaking
4 6 magnitude earthquake rattle northern california overnight thursday shake resident san francisco north sacramento
A 4 . 6 - magnitude earthquake rattled Northern California overnight Thursday , <m> shaking </m> residents from San Francisco to north of Sacramento .
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March 14 , 2013 - UNITED STATES -
A 4 . 6 - magnitude earthquake rattled Northern California overnight Thursday , <m> shaking </m> residents from San Francisco to north of Sacramento .
The temblor struck at 2 : 09 a . m . and was centered in Geyserville , about 20 miles north of Santa Rosa , according to the U . S . Geological Survey .
USGS measurements indicated at least 20 smaller earthquakes followed throughout the morning .
The Santa Rosa Press Democrat reported the quake began only one mile below ground level , which is why it was felt across the region .
There were no immediate reports of damage , the newspaper said .
But it woke people up .
More than 60 people reported to USGS's "Did you feel it ? " site , with reports ranging from San Francisco and Oakland to Lake and Yuba counties .
Others reported the shaking on Twitter .
Tectonic Summary - Maacama Fault
The Maacama Fault is mostly a right - lateral strike - slip fault that lies north of Santa Rosa and the immediate San Francisco Bay Area and extends as far north as Ukiah .
It connects to the Rodgers Creek Fault through a complex set of faults between Santa Rosa and Healdsburg , and is thought to be the northward continuation of the Hayward - Rodgers Creek Fault System .
The 2007 Working Group for California Earthquake Probability assigned a total slip rate on the Maacama Fault of approximately 9 mm / yr ( 1 / 3 inches / yr ) , based on the assumption that it continues the slip on the Hayward - Rodgers Creek Fault northward .
The central and northern sections of the fault have been observed to accommodate approximately 7 mm / yr ( 1 / 4 inch / year ) of creep along it .
The Maacama Fault parallels and overlaps the Rodgers Creek Fault , in a geometry that is causing the ground between the faults to subside .
In Sonoma County north of Healdsburg , the Maacama Fault is largely obscured by massive landslides where it passes east of Alexander Valley .
The 2007 Working Group for California Earthquake Probability combined the Maacama and the Garberville Faults into single a 181 - km ( 110 mile ) long fault and determined M7 . 5 as the maximum magnitude for this combined fault system .
There is very little known about the seismic history or earthquake cycle of the Maacama Fault , and as such recurrence intervals are uncertain .