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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.
Seismology is the scientific study of earthquakes and the generation and propagation of elastic waves through the Earth or other planetary bodies. It also includes studies of earthquake environmental effects such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, glacial, fluvial, oceanic microseism, atmospheric, and artificial processes such as explosions and human activities. A related field that uses geology to infer information regarding past earthquakes is paleoseismology. A recording of Earth motion as a function of time, created by a seismograph is called a seismogram. A seismologist is a scientist works in basic or applied seismology.
Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the next strong earthquake to occur in a region". Earthquake prediction is sometimes distinguished from earthquake forecasting, which can be defined as the probabilistic assessment of general earthquake hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. Not all scientists distinguish "prediction" and "forecast", but the distinction is useful.
In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousands of instrumentally detectable aftershocks, which steadily decrease in magnitude and frequency according to a consistent pattern. In some earthquakes the main rupture happens in two or more steps, resulting in multiple main shocks. These are known as doublet earthquakes, and in general can be distinguished from aftershocks in having similar magnitudes and nearly identical seismic waveforms.
The New Madrid Seismic Zone (NMSZ), sometimes called the New Madrid Fault Line, is a major seismic zone and a prolific source of intraplate earthquakes in the Southern and Midwestern United States, stretching to the southwest from New Madrid, Missouri.
A foreshock is an earthquake that occurs before a larger seismic event – the mainshock – and is related to it in both time and space. The designation of an earthquake as foreshock, mainshock or aftershock is only possible after the full sequence of events has happened.
Aykut Barka was a Turkish geoscientist specialized in seismology. He is best known for his contributions to understanding the behaviour of the North Anatolian Fault Zone (NAFZ), one of the most dangerous active faults in the world.
Coulomb stress transfer is a seismic-related geological process of stress changes to surrounding material caused by local discrete deformation events. Using mapped displacements of the Earth's surface during earthquakes, the computed Coulomb stress changes suggest that the stress relieved during an earthquake not only dissipates but can also move up and down fault segments, concentrating and promoting subsequent tremors. Importantly, Coulomb stress changes have been applied to earthquake-forecasting models that have been used to assess potential hazards related to earthquake activity.
The 1950 Assam–Tibet earthquake, also known as the Assam earthquake, occurred on 15 August and had a moment magnitude of 8.7. The epicentre was located in the Mishmi Hills. It is the strongest earthquake ever recorded on land.
The Queen Charlotte Fault is an active transform fault that marks the boundary of the North American plate and the Pacific plate. It is Canada's right-lateral strike-slip equivalent to the San Andreas Fault to the south in California. The Queen Charlotte Fault forms a triple junction south with the Cascadia subduction zone and the Explorer Ridge. The Queen Charlotte Fault (QCF) forms a transpressional plate boundary, and is as active as other major transform fault systems in terms of slip rates and seismogenic potential. It sustains the highest known deformation rates among continental or continent-ocean transform systems globally, accommodating greater than 50mm/yr dextral offset. The entire approximately 900 km offshore length has ruptured in seven greater than magnitude 7 events during the last century, making the cumulative historical seismic moment release higher than any other modern transform plate boundary system.
Earthquake forecasting is a branch of the science of seismology concerned with the probabilistic assessment of general earthquake seismic hazard, including the frequency and magnitude of damaging earthquakes in a given area over years or decades. While forecasting is usually considered to be a type of prediction, earthquake forecasting is often differentiated from earthquake prediction, Earthquake forecasting estimates the likelihood of earthquakes in a specific timeframe and region, while earthquake prediction attempts to pinpoint the exact time, location, and magnitude of an impending quake, which is currently not reliably achievable.Wood & Gutenberg (1935). Kagan says: "This definition has several defects which contribute to confusion and difficulty in prediction research." In addition to specification of time, location, and magnitude, Allen suggested three other requirements: 4) indication of the author's confidence in the prediction, 5) the chance of an earthquake occurring anyway as a random event, and 6) publication in a form that gives failures the same visibility as successes. Kagan & Knopoff define prediction "to be a formal rule where by the available space-time-seismic moment manifold of earthquake occurrence is significantly contracted ...."</ref> Both forecasting and prediction of earthquakes are distinguished from earthquake warning systems, which, upon detection of an earthquake, provide a real-time warning to regions that might be affected.
QuakeFinder is a company focused on developing a system for earthquake prediction. QuakeFinder operates as a project of aerospace engineering firm Stellar Solutions, and by subscriptions and sponsorships from the public.
The 2011 Oklahoma earthquake was a 5.7 magnitude intraplate earthquake which occurred near Prague, Oklahoma on November 5 at 10:53 p.m. CDT in the U.S. state of Oklahoma. The epicenter of the earthquake was in the vicinity of several active wastewater injection wells. According to the United States Geological Survey (USGS), it was the most powerful earthquake ever recorded in Oklahoma until the 2016 Oklahoma earthquake. The previous record was a 5.5 magnitude earthquake that struck near the town of El Reno in 1952. The quake's epicenter was approximately 44 miles (71 km) east-northeast of Oklahoma City, near the town of Sparks and was felt in the neighboring states of Texas, Arkansas, Kansas and Missouri and even as far away as Tennessee and Wisconsin. The quake followed several minor quakes earlier in the day, including a 4.7 magnitude foreshock. The quake had a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale in the area closest to the epicenter. Numerous aftershocks were detected after the main quake, with a few registering at 4.0 magnitude.
The 2014 Murmuri earthquake occurred on August 18 in the Zagros Mountains of Iran with a moment magnitude of 6.2 and a maximum Mercalli intensity of VIII (Severe). The thrust earthquake injured 60–330 people and was followed by a number of high intensity aftershocks.
An earthquake occurred in southern Mongolia on December 4, 1957, measuring Mw 7.8–8.1 and assigned XII (Extreme) on the Modified Mercalli intensity scale. Surface faulting was observed in the aftermath with peak vertical and horizontal scarp reaching 9 m (30 ft). Because of the extremely sparse population in the area, this event, despite its magnitude, was not catastrophic. However, 30 people died and the towns of Dzun Bogd, Bayan-leg and Baruin Bogd were completely destroyed.
Jeanne L. Hardebeck is an American research geophysicist studying earthquakes and seismology who has worked at the United States Geological Survey (USGS) since 2004. Hardebeck studies the state of stress and the strength of faults.
Shamita Das is an emeritus professor at the University of Oxford and an emeritus fellow at Exeter College. She is known for her research on earthquakes, in particular the speed that earthquakes can propagate through the earth.
The 1995 Menglian earthquake or 1995 Myanmar–China earthquake occurred on 12 July at 05:46:43 local time in the Myanmar–China border region. The earthquake had an epicenter on the Myanmar side of the border, located in the mountainous region of Shan State. It registered 7.3 on the Chinese surface wave magnitude scale (Ms ) and 6.8 on the moment magnitude scale (Mw ). With a maximum Mercalli intensity assigned at VIII, it killed 11 people and left another 136 injured. Over 100,000 homes in both countries were destroyed and 42,000 seriously damaged. Some damage to structures were also reported in Chiang Mai and Chiang Rai, Thailand. The low death toll from this earthquake was attributed to an early warning issued prior to it happening. Precursor events including foreshocks and some seismic anomalies led to an evacuation of the area before the mainshock struck. It is thought to be one of the few successfully predicted earthquakes in history.
The earthquake cycle refers to the phenomenon that earthquakes repeatedly occur on the same fault as the result of continual stress accumulation and periodic stress release. Earthquake cycles can occur on a variety of faults including subduction zones and continental faults. Depending on the size of the earthquake, an earthquake cycle can last decades, centuries, or longer. The Parkfield portion of the San Andreas fault is a well-known example where similarly located M6.0 earthquakes have been instrumentally recorded every 30–40 years.
The 1992 Joshua Tree earthquake occurred at 9:50:25 p.m. PDT on April 22 in Southern California. The magnitude 6.2 earthquake struck under the Little San Bernardino Mountains, near the town of Joshua Tree, California. Though no deaths were reported, the earthquake caused 32 injuries. A maximum Mercalli intensity of VII was observed in Joshua Tree and caused light to moderate damage. The event preceded the Landers and Big Bear earthquakes by two months but is now recognized as the beginning of a series of major earthquakes that culminated in two events on June 28, 1992.
References
- 1 2 3 4 Rice, James R. "James H. Dieterich". American Geophysical Union .
- 1 2 Pittalwala, Iqbal (September 19, 2011). "Geophysicists to Develop Computer Simulations of Earthquake Fault Systems".
- ↑ "Exploring Earthquake Prediction and Impacts". University of California, Riverside . November 4, 2013. Archived from the original on June 28, 2020. Retrieved March 2, 2015.
- ↑ Opar, Alisa (March 1, 2010). "Scientists Aim to Predict Earthquakes Months or Years Out, Not Days Before". National Audubon Society .
- ↑ Pittalwala, Iqbal (May 30, 2007). "Two UCR Earth Scientists Honored with U.S. Geological Survey's Distinguished Service Awards" (Press release).
- ↑ Orville, Philip M., ed. (October 27, 1968). "Guidebook for Fieldtrips in Connecticut: New England Intercollegiate Geological Conference". Yale University.
{{cite journal}}: Cite journal requires|journal=(help) - ↑ Monastersky, Richard (July 24, 1993). "Where Have All the Earthquakes Gone? Scientists Wonder Why Part of Hawaii's Kilauea Volcano Has Gone Quiet". Science News.[ dead link ]
- 1 2 "Mary Lou Zoback and James Dieterich: Survey scientists in the National Academy". GeoTimes. American Geophysical Institute. June 2003.
- ↑ Booz Allen & Hamilton; LabatAnderson, Inc. (April 24, 1989). "Activity Profiles and Chronologies of the Non-Relief Projects of the Office of U.S. Foreign Disaster Assistance 1979-1988" (PDF). USAID: 89.
{{cite journal}}: Cite journal requires|journal=(help) - ↑ Lee, William H.K.; Kanamori, Hiroo; Jennings, Paul; Kisslinger, Carl (2003). International Handbook of Earthquake & Engineering Seismology, Part 2. Vol. 81. Academic Press. pp. 1222–1223. ISBN 9780080489230.
- ↑ Marone, Chris (September 5, 2002). "Stressed to quaking point" (PDF). Nature . 419 (6902): 32. doi:10.1038/419032a. PMID 12214222. S2CID 4303624.
- ↑ Salleh, Anna (September 6, 2002). "Earthquake forecasts given a boost". ABC Online .
- ↑ Peterson, Greg (November 2002). "Many quakes, one theory". GeoTimes.
- ↑ United States Geological Survey (September 5, 2002). "New Evidence For Why Earthquake Swarms Occur Offers Hope For Better Earthquake Forecasting". Science Daily (Press release).
- ↑ Fiegener, Craig (October 13, 2011). "$4.6 Million for Earthquake Research at UC Riverside". KNBC.
- ↑ Dybas, Cheryl (September 30, 2011). "NSF Frontiers in Earth-System Dynamics Awards Explore Links Among Earth Processes and Systems". National Science Foundation .
- ↑ "NSF Awards $4.6M for Earthquake Study". San Diego State University . September 26, 2011.