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An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.
The San Andreas Fault is a continental right-lateral strike-slip transform fault that extends roughly 1,200 kilometers (750 mi) through the U.S. state of California. It forms part of the tectonic boundary between the Pacific plate and the North American plate. Traditionally, for scientific purposes, the fault has been classified into three main segments, each with different characteristics and a different degree of earthquake risk. The average slip rate along the entire fault ranges from 20 to 35 mm per year.
In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period. The time span used to define a swarm varies, but may be days, months, or years. Such an energy release is different from the situation when a major earthquake is followed by a series of aftershocks: in earthquake swarms, no single earthquake in the sequence is obviously the main shock. In particular, a cluster of aftershocks occurring after a mainshock is not a swarm.
The Sawtooth Wilderness is a federally-protected wilderness area that covers 217,088 acres (87,852 ha) of the state of Idaho. Managed by the U.S. Forest Service in the U.S. Department of Agriculture, it was designated the Sawtooth Primitive Area in 1937 to preserve the scenic beauty of the Sawtooth Mountains. On August 22, 1972 Public Law 92-400 designated the Primitive Area as the Sawtooth Wilderness and part of the newly created Sawtooth National Recreation Area. As part of the National Wilderness Preservation System, the Sawtooth Wilderness is an area where human development and use are restricted and people are to remain only visitors. According to the United States Environmental Protection Agency, the Sawtooth Wilderness has some of the clearest air in the lower 48 states.
Sawtooth National Forest is a National Forest that covers 2,110,408 acres in the U.S. states of Idaho and Utah. Managed by the U.S. Forest Service in the U.S. Department of Agriculture, it was originally named the Sawtooth Forest Reserve in a proclamation issued by President Theodore Roosevelt on May 29, 1905. On August 22, 1972, a portion of the forest was designated as the Sawtooth National Recreation Area (SNRA), which includes the Sawtooth, Cecil D. Andrus–White Clouds, and Hemingway–Boulders wilderness areas. The forest is managed as four units: the SNRA and the Fairfield, Ketchum, and Minidoka Ranger Districts.
The Wasatch Fault is an active fault located primarily on the western edge of the Wasatch Mountains in the U.S. states of Utah and Idaho. The fault is about 240 miles long, stretching from southern Idaho, through northern Utah, before terminating in central Utah near the town of Fayette. The fault is made up of ten segments, five of which are considered active. On average the segments are approximately 25 miles long, each of which can independently produce earthquakes as powerful as local magnitude 7.5. The five active segments from north to south are called the Brigham City Fault Segment, the Weber Fault Segment, the Salt Lake City Fault Segment, the Provo Fault Segment and the Nephi Fault Segment.
The Sawtooth National Recreation Area (SNRA) is a national recreation area in central Idaho, United States that is managed as part of Sawtooth National Forest. The recreation area, established on August 22, 1972, is managed by the U.S. Forest Service, and includes the Sawtooth, Hemingway–Boulders, and Cecil D. Andrus–White Clouds wilderness areas. Activities within the 730,864-acre (2,957.70 km2) recreation area include hiking, backpacking, White water rafting, camping, rock climbing, kayaking, mountain biking, fishing, and hunting.
The Blanco Fracture Zone or Blanco Transform Fault Zone (BTFZ) is a right lateral transform fault zone, which runs northwest off the coast of Oregon in the Pacific Northwest of the United States, extending from the Gorda Ridge in the south to the Juan de Fuca Ridge in the north.
The Sawtooth Range is a mountain range of the Rocky Mountains in central Idaho, United States, reaching a maximum elevation of 10,751 feet (3,277 m) at the summit of Thompson Peak. It encompasses an area of 678 square miles (1,756 km2) spanning parts of Custer, Boise, Blaine, and Elmore counties, and is bordered to the east by the Sawtooth Valley. Much of the mountain range is within the Sawtooth Wilderness, part of the Sawtooth National Recreation Area and Sawtooth National Forest.
The U.S. state of Idaho borders six other U.S. states and one Canadian province. The states of Washington and Oregon are to the west, Nevada and Utah are to the south, and Montana and Wyoming are to the east. Idaho also shares a short border with the Canadian province of British Columbia to the north.
State Highway 75 is a two-lane highway in the western United States that travels through the Sawtooth Valley of central Idaho. The highway's southern terminus is in Shoshone, and its northern is near Challis. It is designated as one of Idaho's scenic byways and provides access to Sawtooth National Recreation Area and primarily follows the Big Wood River in the south and the main Salmon River in the north, divided by Galena Summit.
The 1983 Borah Peak earthquake occurred on October 28, at 8:06:09 a.m. MDT in the western United States, in the Lost River Range at Borah Peak in central Idaho.
The Enriquillo–Plantain Garden fault zone is a system of active coaxial left lateral-moving strike slip faults which runs along the southern side of the island of Hispaniola, where Haiti and the Dominican Republic are located. The EPGFZ is named for Lake Enriquillo in the Dominican Republic where the fault zone emerges, and extends across the southern portion of Hispaniola through the Caribbean to the region of the Plantain Garden River in Jamaica.
The 1916 Irondale earthquake struck in the north-central region of the U.S. state of Alabama on October 18. The strongest earthquake in state history, it registered an estimated Richter scale magnitude of 5.1 and resulted in minor damage. Damage was limited to Shelby and Jefferson counties and reached its maximum severity near the epicenter in the city of Irondale, including cracked windows, fallen chimneys, and dried-up wells. While there were no fatalities, the earthquake spawned widespread panic, prompting alarmed workers to evacuate tall buildings.
The Teton fault is a normal fault located in northwestern Wyoming. The fault has a length of 44 miles (70 km) and runs along the eastern base of the Teton Range. Vertical movement on the fault has caused the dramatic topography of the Teton Range.
At 7:09 AM MDT on March 18, 2020, a 5.7 magnitude earthquake hit Salt Lake City, Utah, United States, with an epicenter 6 km (3.7 mi) north-northeast of Magna, Utah, beneath the site of the planned Utah Inland Port. It was the first major earthquake to occur within the Salt Lake Valley since the city was founded, the state's strongest earthquake since the 1992 St. George earthquake, and the first earthquake of comparable magnitude to occur near Salt Lake City since 1962, when a magnitude 5.0 earthquake struck a similar location in Magna.
The 1934 Hansel Valley earthquake occurred on March 12 at approximately 8:05 a.m. MST with a moment magnitude of 6.6 and a maximum Mercalli intensity of VIII (Severe). The shock originated in the Hansel Valley at the north end of the Great Salt Lake in Utah in the United States. Damage was mostly confined to vulnerable buildings, and two people died. The dip-slip (normal) fault that generated the shock ruptured the surface of the ground and other geologic features were documented. A large aftershock occurred three hours after the initial event and may have caused additional damage.
The 2020 Central Idaho earthquake occurred in the western United States on March 31, 2020, at 5:52 PM MDT, near Ruffneck Peak in the Sawtooth Mountains of central Idaho, 72 miles (116 km) northeast of Boise and 19 miles (31 km) northwest of Stanley. It had a magnitude of 6.5 and was felt with a maximum intensity of VIII.
The 1968 Borrego Mountain earthquake occurred on April 8, at 18:28 PST in the geologically active Salton Trough of Southern California. The Salton Trough represents a pull-apart basin formed by movements along major faults. This region is dominated by major strike-slip faults one of them being the San Jacinto Fault which produced the 1968 earthquake. The mainshock's epicenter was near the unincorporated community of Ocotillo Wells in San Diego County. The moment magnitude (Mw ) 6.6 strike-slip earthquake struck with a focal depth of 11.1 km (6.9 mi). The zone of surface rupture was assigned a maximum Modified Mercalli intensity (MMI) of VII.
The 1850 Xichang earthquake rocked Sichuan Province of Qing China on September 12. The earthquake which caused major damage in Xichang county had an estimated moment magnitude of 7.3–7.9 Mw and a surface wave magnitude of 7.5–7.7 Ms . An estimated 20,650 people died.
References
- ↑ "Scientists find new seismic fault in Rocky Mountains". BBC News. May 20, 2012. Archived from the original on July 20, 2012. Retrieved November 20, 2010.
- ↑ Wall, Tim (November 19, 2010). "Large Seismic Fault Found in the Rockies". Discovery News. Archived from the original on June 22, 2013. Retrieved November 20, 2010.
- ↑ "Geosciences Professor Discovers New Fault". Idaho State University. September 27, 2010. Archived from the original on April 11, 2013. Retrieved March 9, 2013.
- ↑ "M 6.5 – 72 km W of Challis, Idaho". United States Geological Survey. March 31, 2020. Retrieved March 31, 2020.
- ↑ Nicole Blanchard (April 8, 2020). "A week after Idaho's earthquake, experts seek answers about historic, unexpected event". The Idaho Statesman. McClatchy.com. Retrieved April 9, 2020.
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