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An earthquake – also called a quake, tremor, or temblor – is the shaking of the surface of Earth resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those that are so weak that 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 word tremor is also used for non-earthquake seismic rumbling.
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.
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.
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, whose goal is the specification of the time, location, and magnitude of future earthquakes with sufficient precision that a warning can be issued. 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.
The Dasht-e Bayaz and Ferdows earthquakes occurred in Dashte Bayaz, Kakhk and Ferdows, Iran in late August and early September 1968. The mainshock measured 7.4 on the moment magnitude scale and had a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. Damage was heavy in the affected areas with thousands of lives lost in the first event and many hundreds more in the second strong event.
The Brawley Seismic Zone (BSZ), also known as the Brawley fault zone, is a predominantly extensional tectonic zone that connects the southern terminus of the San Andreas Fault with the Imperial Fault in Southern California. The BSZ is named for the nearby town of Brawley in Imperial County, California, and the seismicity there is characterized by earthquake swarms.
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; this record was surpassed by 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 1931 Myitkyina earthquake, or also known as the 1931 Kamaing earthquake, occurred on January 28 at 02:35 local time. It was located in northern Burma, then part of British India. The magnitude of this earthquake was put at Mw 7.6. According to some sources the depth was 35 km, and according to a study of Phyo M. M. the depth was 5 to 30 km.
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 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 1979 Yapen earthquake occurred on September 12 at 05:17:51 UTC. It had an epicenter near the coast of Yapen Island in Irian Jaya, Indonesia. Measuring 7.5 on the moment magnitude scale and having a depth of 20 km (12 mi), it caused severe damage on the island. At least 115 were killed due to shaking and a moderate tsunami.
The 1979 Saint Elias earthquake occurred near noon local time on the 28th of February. It measured Mw 7.4–7.6. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. The epicenter lies near the Alaskan border between America and Canada.
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.