The Sawtooth Fault is an east- dipping

normal fault In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...

(vertical motion) which runs along the eastern base of the Sawtooth Mountains in the state of

Idaho Idaho ( ) is a state in the Pacific Northwest region of the Western United States. To the north, it shares a small portion of the Canada–United States border with the province of British Columbia. It borders the states of Montana and Wyom ...

in the United States. In 2010, Glenn Thackray and colleagues from

Idaho State University , mottoeng = "The truth will set you free" , established = , former_names = Academy of Idaho(1901–1915)Idaho Technical Institute(1915–1927)University of Idaho—Southern Branch(1927–1947)Idaho State ...

discovered the Sawtooth Fault near the base of the mountains using

LIDAR Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be ...

. They found that it could produce an

earthquake An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, from ...

measuring up to magnitude 7.5 and that two past large earthquakes likely took place on the fault around 7,000 and 4,000 years ago. The fault is long, and runs near

Stanley, Idaho Stanley is a town in the Sawtooth Valley in Custer County, Idaho, United States. The population was 116 at the 2020 census; up from 63 in 2010. The center of population of Idaho in 2000 was located in Stanley. History Fur trappers of the Hud ...

and

Redfish Lake Redfish Lake is an alpine lake in Custer County, Idaho, just south of Stanley. It is the largest lake within the Sawtooth National Recreation Area. The U.S. Forest Service has developed some facilities for hiking, camping, and water sports on Red ...

. Future earthquakes could be felt as far as

Boise Boise (, , ) is the capital and most populous city of the U.S. state of Idaho and is the county seat of Ada County. On the Boise River in southwestern Idaho, it is east of the Oregon border and north of the Nevada border. The downtown area's ...

. On March 31st, 2020, the 6.5

magnitude Magnitude may refer to: Mathematics *Euclidean vector, a quantity defined by both its magnitude and its direction *Magnitude (mathematics), the relative size of an object *Norm (mathematics), a term for the size or length of a vector *Order of ...

2020 Central Idaho earthquake struck about 16 km north-northeast of the Sawtooth Fault. However, this quake is likely not on the Sawtooth Fault as it had strike-slip motion rather than up-down motion of a normal fault.

References

''Lacustrine Evidence of Seismic Events on the Sawtooth Fault in the Redfish Lake Drainage, Sawtooth Mountains, Central Idaho'', Eric M. Johnson, Thesis, Idaho State University, April 2010
Landforms of Custer County, Idaho {{tectonics-stub