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Foreshock
A foreshock is an earthquake that occurs before a larger seismic eventthe mainshockand 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. Occurrence Foreshock activity has been detected for about 40% of all moderate to large earthquakes, and about 70% for events of M>7.0. They occur from a matter of minutes to days or even longer before the main shock; for example, the 2002 Sumatra earthquake is regarded as a foreshock of the 2004 Indian Ocean earthquake with a delay of more than two years between the two events. Some great earthquakes (M>8.0) show no foreshock activity at all, such as the M8.6 1950 Assam–Tibet earthquake, 1950 India–China earthquake. The increase in foreshock activity is difficult to quantify for individual earthquakes but becomes apparent when combining the results of many different events. From such combined observations, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1975 Haicheng Earthquake
On February 4, 1975, at 19:36 Chinese Standard Time, CST, an earthquake of 7.5 and Modified Mercalli intensity scale, intensity (MMI) IX hit the city of Haicheng, Liaoning, China. Much of the city was evacuated before the earthquake, so few died from building collapse; however, many died from fire and hypothermia in the subsequent days. The evacuees lived during the deep winter in self-made tents made of tree branches, bed sheets, Tarpaulin, tarps and straw,Photos of such tents taken in 1976 can be found in: 372 froze to death and 6,578 suffered frostbite, while a fire burned 341 to death and 980 suffered non-fatal burns.颤抖的地球—地震科学' (2005). Researched by CEA seismologists 冯万鹏,薑文亮,龚丽霞,公茂盛,胡进军; Revised by CEA seismologists 王文清,续春荣,张宝红; Edited by China Earthquake Administration, CEA chiefs 谢礼立,张景发. Tsinghua University Press. Pages XIII, 162. The fire was one of the most notable earthquake-induced List o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aftershock
In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in Epicenter, the same area of the Mainshock, main shock, caused as the displaced Crust (geology), 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 #Aftershock size and frequency with time, 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. Distribution of aftershocks Most aftershocks are located over the full area of fault rupture and either occur along the fault plane itself or along other faults within the volume affected by the strain associated with the main shock. Typically, aftershocks are found up to a d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake Prediction
Earthquake prediction is a branch of the science of geophysics, primarily 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. Prediction can be further distinguished from earthquake warning systems, which, upon detection of an earthquake, provide a real-time warning of seconds to neighboring regions that might be affected. In the 1970s, scientists were optimistic that a practical method for predicting earthquakes would soon be found, but by the 1990s continuing failure led many to question whether it was even possible. Demonstrabl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mainshock
In seismology, the mainshock is the largest earthquake in a sequence, sometimes preceded by one or more foreshocks, and almost always followed by many aftershocks. Foreshock 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. Aftershock 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 known laws. In some earthquakes the main rupture happens in two or more steps, resulting in multiple main shocks. These are known as doublet earthquakes Doublet is a word de ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2002 Sumatra Earthquake
The 2002 Sumatra earthquake occurred at 08:26:10 WIB (01:26 UTC) on 2 November. It had a magnitude of 7.2–7.4 with an epicenter just north of Simeulue island, and resulted in three fatalities. It is regarded as a foreshock of the 2004 Indian Ocean earthquake, which had an epicenter about 60 km to the northwest. Tectonic setting The island of Sumatra lies on the convergent plate boundary between the Indo-Australian plate and the Eurasian plate. The convergence between these plates is highly oblique near Sumatra, with the displacement being accommodated by near pure dip-slip faulting along the subduction zone, known as the Sunda megathrust, and near pure strike-slip faulting along the Great Sumatran fault. The major slip events on the subduction zone interface are typically of megathrust type. Historically, great or giant megathrust earthquakes have been recorded in 1797, 1833, 1861, 2004, 2005 and 2007, most of them being associated with devastating tsunamis. S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1904 Kresna Earthquakes
The 1904 Kresna earthquakes occurred on the same day of April 4 in the Kresna region of Bulgaria. The pair of earthquakes measured 6.9 and 7.2 on the surface wave magnitude scale, and were assigned the respective Modified Mercalli intensity scale ratings of X (''Extreme'') and XI (''Extreme''). More than 200 people were killed in the two earthquakes. Several villages were obliterated as a result. Earthquakes The first shock occurred in the morning of April 4 at 11:58 local time. It had an epicenter located in the Struma River Valley between the then villages of Kresna and Krupnik. A larger mainshock occurred approximately 20 minutes later. The two earthquakes resulted in the total destruction of Simitli and Krupnik. Major damage occurred in the towns of Dzhumaya, Bansko and Razlog. The two quakes caused more than 200 deaths in its aftermath. According to survivors of the earthquakes, farm cattle began to gather in a group and displayed signs of distress before the earthqu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1960 Valdivia Earthquake
The 1960 Valdivia earthquake and tsunami () or the Great Chilean earthquake (''Gran terremoto de Chile'') occurred on 22 May 1960. Most studies have placed it at 9.5–9.6 on the moment magnitude scale, while some studies have placed the magnitude lower than 9.4, making it the most powerful earthquake ever recorded. It occurred in the afternoon (19:11:14 GMT, 15:11:14 local time), and lasted 10 minutes. The resulting tsunamis affected southern Chile, Hawaii, Japan, the Philippines, eastern New Zealand, southeast Australia, and the Aleutian Islands. The epicenter of this megathrust earthquake was near Lumaco, approximately south of Santiago, with Valdivia being the most affected city. The tremor caused localised tsunamis that severely battered the Chilean coast, with waves up to . The main tsunami traveled across the Pacific Ocean and devastated Hilo, Hawaii, where waves as high as were recorded over from the epicenter. The death toll and monetary losses arising from this ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2004 Indian Ocean Earthquake
On 26 December 2004, at 07:58:53 local time (UTC+07:00, UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicenter, epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The Submarine earthquake, undersea megathrust earthquake, known in the scientific community as the Sumatra–Andaman earthquake, was caused by a rupture along the fault between the Burma plate and the Indian plate, and reached a Modified Mercalli intensity scale, Mercalli intensity of IX in some areas. A massive tsunami with waves up to high, known as the Boxing Day Tsunami after the Boxing Day holiday, or as the Asian Tsunami, devastated communities along the surrounding coasts of the Indian Ocean, killing an estimated 227,898 people in 14 countries, violently in Aceh (Indonesia), and severely in Sri Lanka, Tamil Nadu (India), and Khao Lak (Thailand). The direct result was major disruption to living conditions and commerce in coastal provinces of surrounding countries. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
1960 Concepción Earthquakes
The 1960 Concepción earthquakes were a succession of three destructive earthquakes that happened between 21 and 22 May 1960. They formed part of the foreshock sequence for the 1960 Valdivia earthquake, the largest recorded earthquake in history. The first was on May 21 at 06:02 UTC-4.Servicio Sismológico Universidad de ChileSismos importantes o destructivos desde 1570 Its epicenter was near Cañete, Bío Bío Region, Chile, and its magnitude was 8.1 or 8.3 MW and 7.3 or 7.5 MS. This earthquake, which lasted 35 seconds, destroyed a third of the buildings in the city of Concepción. The earthquake effectively interrupted and ended Lota's coal miners march on Concepción where they demanded higher salaries. The second happened on May 22 at 06:30 UTC-4. Its epicenter was in the Nahuelbuta National Park, Araucanía Region, Chile, and its magnitude was 7.1 Mw. It was followed by a 6.8 Mw earthquake at 06:32 UTC-4. The third happened the same day at 14:56 UTC ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
2004 Indian Ocean Earthquake And Tsunami
On 26 December 2004, at 07:58:53 local time ( UTC+7), a major earthquake with a magnitude of 9.2–9.3 struck with an epicentre off the west coast of Aceh in northern Sumatra, Indonesia. The undersea megathrust earthquake, known in the scientific community as the Sumatra–Andaman earthquake, was caused by a rupture along the fault between the Burma plate and the Indian plate, and reached a Mercalli intensity of IX in some areas. A massive tsunami with waves up to high, known as the Boxing Day Tsunami after the Boxing Day holiday, or as the Asian Tsunami, devastated communities along the surrounding coasts of the Indian Ocean, killing an estimated 227,898 people in 14 countries, violently in Aceh (Indonesia), and severely in Sri Lanka, Tamil Nadu (India), and Khao Lak (Thailand). The direct result was major disruption to living conditions and commerce in coastal provinces of surrounding countries. It is the deadliest natural disaster of the 21st century, one of the d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earthquake
An earthquakealso called a quake, tremor, or tembloris 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. In its most general sense, the word ''earthquake'' is used to describe any seismic event that generates seismic waves. Earthquakes can occur naturally or be induced by human activities, such as mining, fracking, and nuclear weapons testing. The initial point of rupture is called the hypocenter or focus, while the ground level directly above it is the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
