An intraplate earthquake is an earthquake that occurs in the interior of a tectonic plate, in contrast to an interplate earthquake on the boundary of a tectonic plate. It is also called an intraslab earthquake, especially when occurring in a microplate.
The moment magnitude scale is a measure of an earthquake's magnitude based on its seismic moment. Mw was defined in a 1979 paper by Thomas C. Hanks and Hiroo Kanamori. Similar to the local magnitude/Richter scale (ML ) defined by Charles Francis Richter in 1935, it uses a logarithmic scale; small earthquakes have approximately the same magnitudes on both scales. Despite the difference, news media often use the term "Richter scale" when referring to the moment magnitude scale.
Induced seismicity is typically earthquakes and tremors that are caused by human activity that alters the stresses and strains on Earth's crust. Most induced seismicity is of a low magnitude. A few sites regularly have larger quakes, such as The Geysers geothermal plant in California which averaged two M4 events and 15 M3 events every year from 2004 to 2009. The Human-Induced Earthquake Database (HiQuake) documents all reported cases of induced seismicity proposed on scientific grounds and is the most complete compilation of its kind.
Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary based on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.
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.
The 1999 Athens earthquake occurred on September 7 at near Mount Parnitha in Greece with a moment magnitude of 6.0 and a maximum Mercalli intensity of IX (Violent). The proximity to the Athens metropolitan area resulted in widespread structural damage, mainly to the nearby suburban towns of Ano Liosia, Acharnes, Fyli, Thrakomakedones, Kifissia, Metamorfosi, Kamatero and Nea Filadelfeia. More than 100 buildings across those areas collapsed trapping scores of victims under their rubble while dozens more were severely damaged. With damage estimated at $3–4.2 billion, 143 people were killed, and up to 1,600 were treated for injuries in Greece's deadliest natural disaster in almost half a century.
The 2008 Illinois earthquake was one of the largest earthquakes ever recorded in the Midwest state of Illinois. This moderate strike-slip shock measured 5.2 on the moment magnitude scale and had a maximum Mercalli intensity of VII (Very strong). It occurred at on April 18 near Bellmont and Mount Carmel, Illinois, within the Wabash Valley Seismic Zone. Earthquakes in this part of the country are often felt at great distances.
Body-waves consist of P-waves that are the first to arrive, or S-waves, or reflections of either. Body-waves travel through rock directly.
This list of 20th-century earthquakes is a list of earthquakes of magnitude 6 and above that occurred in the 20th century. Sone smaller events which nevertheless had a significant impact are also included. After 1900 most earthquakes have some degree of instrumental records and this means that the locations and magnitudes are more reliable than for earlier events.
In seismology, doublet earthquakes – and more generally, multiplet earthquakes – were originally identified as multiple earthquakes with nearly identical waveforms originating from the same location. They are now characterized as distinct earthquake sequences having two main shocks of similar magnitude, sometimes occurring within tens of seconds, but sometimes separated by years. The similarity of magnitude – often within 0.4 magnitude – distinguishes multiplet events from aftershocks, which start at about 1.2 magnitude less than the parent shock and decrease in magnitude and frequency according to known laws.
In seismology, a tsunami earthquake is an earthquake which triggers a tsunami of significantly greater magnitude, as measured by shorter-period seismic waves. The term was introduced by Japanese seismologist Hiroo Kanamori in 1972. Such events are a result of relatively slow rupture velocities. They are particularly dangerous as a large tsunami may arrive at a coastline with little or no warning.
The 2001 Geiyo earthquake occurred with a moment magnitude of 6.7 on March 24 at near Hiroshima, Japan. One person in Hiroshima and one person in Ehime were reported dead. About 3,700 buildings were damaged in the Hiroshima area. Liquefaction was observed in Hiroshima and Ehime. Power outages occurred in the prefectures of Hiroshima, Ehime, Okayama, Yamaguchi, and Kōchi. The maximum intensity was shindo lower 6 in Hiroshima. This earthquake could be felt along the eastern and southern coasts of South Korea.
The 1839 Martinique earthquake occurred on the morning of January 11 with an estimated magnitude of 7.8 Ms , the largest in the Lesser Antilles since 1690. The maximum intensity of this earthquake was assigned IX on both the Mercalli and MSK intensity scales, which left the cities of Saint-Pierre and Fort Royal almost completely destroyed. Estimation on the number of human losses varies from 390 to 4,000 making this one of the deadliest earthquakes in the Caribbean.
The 1920 Xalapa earthquake affected the Trans-Mexican Volcanic Belt in the states of Puebla and Veracruz, Mexico on 3 January at 22:25 CST. It was the second deadliest to affect Mexico, behind the 1985 Mexico City earthquake. The earthquake measured 6.3–6.4 on the moment magnitude scale. An area around the epicenter, located between Chilchotla and Patlanalán, was assigned the maximum intensity of XI–XII (Extreme) on the Modified Mercalli intensity scale. Aftershocks following the earthquake were studied to determine that it originated at a depth of 15 km (9.3 mi) of less. The focal mechanism indicated that the shock was the result of faulting along an east–west striking normal fault beneath the volcanic belt.
The 1909 Benavente earthquake occurred on 23 April at 17:39:36 local in the Santarém District of the Central Region, Portugal. The estimated moment magnitude 6.0–6.3 earthquake had a maximum Mercalli intensity of IX (Violent). It nearly destroyed the town of Benavente, killing 60 and injuring 75 people as a result.
The 1867 Central Java earthquake occurred on June 10 at between 04:20 and 04:30 local time. It struck off the southern coast of the Indonesian island with an estimated moment magnitude of 7.8 (Mw ). Widespread devastation occurred in Central Java, where as many as 700 people were killed. The intermediate-depth intraslab earthquake did not cause a tsunami.
The 1979 Saint Elias earthquake affected Alaska at 12:27 AKST on 28 February. The thrust-faulting 7.5 earthquake had an epicenter in the Granite Mountains. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. Damage also extended across the border in parts of Yukon, Canada.
