![]() ![]() The greater San Francisco Bay Area has a high likelihood of future damaging earthquakes as it straddles the San Andreas fault system-the major geologic boundary between the North American and Pacific tectonic plates.What is the Earthquake Risk in San Francisco Even moderate shaking can damage seismically-vulnerable structures and trigger landslides that could quickly block roads and highways.Ĭounties: Alameda, Contra Costa, Marin, Napa, San Francisco, San Mateo, Santa Clara, Solano, Sonoma Very large earthquakes that occur closer to the Northern California coast could cause damaging levels of ground shaking here too.Much of the north-eastern part of the state is actively stretching apart, creating numerous faults, all capable of producing earthquakes. ![]() The Modoc Plateau has both active volcanoes and faults.In addition to volcanoes, this is also earthquake country. The Trinity Mountains, Modoc Plateau, Shasta and Lassen peaks were created by geologic forces that are still shaping the landscape.*The 76% probability of one or more magnitude 7.0 earthquakes striking Northern California is based on a 30-year period, beginning in 2014.Ĭounties: Butte, Glenn, Lassen, Modoc, Plumas, Shasta, Sierra, Siskiyou, Tehama, Trinity See the USGS interactive fault map to learn more about faults in this area Landslides are possible on steep hillsides. Houses on liquefied soil may settle or even move laterally on gentle slopes. Soils in lowland areas away from major faults may be subject to liquefaction.Very large earthquakes occurring close to the coast could cause damaging levels of ground shaking and tsunami waves.20th, 2022, a magnitude 6.4 quake struck a few miles off the coast of Humboldt County, followed by at least a dozen smaller aftershocks. Scientists report that partial ruptures on the southern half of the Cascadia Seismic Zone (which extends into Northern California) have historically generated earthquakes with magnitude 8 or greater.This fault zone is capable of generating a magnitude 9 (or larger) earthquake on average every 500 years.The Cascadia Subduction Zone stretches underneath the Humboldt-Del Norte county region, extending from Cape Mendocino all the way up through the Pacific Northwest.This event had a significant impact on the hydrology of the area and is still visible today.Counties: Del Norte, Humboldt, Lake, Mendocino Interestingly, the Madison River was the location of a large earthquake in 1959, which created a landslide that blocked the river and formed Quake Lake. The river experiences seasonal trends, with peak flow occurring in late spring and early summer due to snowmelt. The river is affected by several dams and tributaries, including Hebgen Lake Dam and its associated tributaries. The flow in the Madison River is primarily provided by snowmelt and precipitation. The Madison River near Grayling, Montana is monitored by a stream gauge located at Hebgen Lake. Light and variable wind becoming southwest 8 to 13 mph in the morning. Otherwise, mostly sunny, with a high near 69. The streamflow average over the past 10 days is 1,106 cfs. Streamflow discharge was last observed at 1,030 cfs, and a gauge height of 1.83 feet. MADISON RIVER BELOW HEBGEN LAKE NEAR GRAYLING ![]()
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