These slides discuss where and why aftershocks occur and include animations of aftershock sequences following two m 5 earthquakes in southern california. Earthquakes occur when a critical amount of stress is applied to the crust. Oct 14, 2009 if earthquakes obeyed the elastic rebound theory, large quakes should reset the seismic clock and there should be a gap before another big shock hit the same region. The seismic gap hypothesis holds that most longterm geo logic slip on faults or plate. A elastic rebound theory b slip on a fault with a uniform stress drop c seismic moment d energy release during an earthquake ii elastic rebound theory h. Over the course of time, one can observe that the two sides of an active fault are in slow but continuous movement relative to one another. As the earths crust deforms, the rocks which span the. Several wellknown premonitory effects such as anomalous variation in the ratio of longitudinal v p and shear v s seismic velocities,v p v s, tilt, regional and local. When the stress becomes too great then the rocks separate and an earthquake results.
In the theory, fault movements are based on the ability of rock to stick to each other while under stress. The elastic rebound theory is now well accepted as the reason for the occurrence of earthquakes. At oberlin, she meets zoe, and the two become friends and eventually lovers. The force per unit area acting on a rock is called stress. This is something like pulling a rubber band gradually until the band snaps. Triggering of aftershocks of the japan 2011 earthquake by. When two faults collide, instead of one breaking past another, they may just merge, like a zipper zipping up, said john platt, a geologist at the university of. As you learned in the plate tectonics chapter, scientists use the location of earthquakes to draw plate boundaries the region around the pacific ocean is called the pacific ring of fire. The masses of rock undergo elastic strain, slowly flexing and moving in opposite directions. From the perspective of elastic rebound theory, they represent the most dramatic part of the seismic. A straight fence is built across the san andreas fault. On earths surface, any straight line like a road or a fence a crossing a fault.
In elastic rebound theory, what must occur to produce an. Elastic rebound theory eventually, the strain along the fault exceeds the limit of the rocks at that point to store any additional strain. Mar 09, 2016 this video discusses the relationship between plate boundaries and earthquakes, deformation, elastic limit and rebound and the 3 kinds of faults earthquakes can happen in. This scenario can happen repeatedly on a 100500 year cycle. The rocks then snap apart, releasing energy in the form of seismic waves figure 10. Earthquakes are caused by active faults, which are, caused by the sudden movement of the two sides of a fault with respect to another. Earthquakes occur when the frictional forces on the fault surfaces are overcome. This lab exercise teaches students about elastic rebound and friction and how these concepts related to earthquakes.
Elastic rebound and friction lab lesson plan by deborah kane and dave van dusen. May 10, 2016 elastic rebound theory is directly related to earthquakes. The three types of directional stress experienced by rocks are compressional, tensional, and shear stress fig. The elastic rebound theory of earthquake sources allows rough prediction of the occurrence of large shallow earthquakes. The 1906 earthquake and a century of progress in understanding. Passing right down the middle of the orchard, and across the road, is a fault zone. Elasticreboundtheory elasticrebound theelasticreboundtheoryisanexplanationforhow energyisspreadduringearthquakes. Is a measure of ground motion determined from seismogram. Tectonics are explained by the socalled elastic rebound theory, formulated by the american geologist harry fielding reid after the san andreas fault ruptured in 1906, generating the great san francisco earthquake. Feb 22, 2014 1 the veolcity of s waves decreases as the waves enter the asthenosphere what does this suggest about the asthenosphere compared to the overlying lithosphere.
Earthquake theory by wanchung hu on 20170511 abstract earthquake is thought to be due to plate tectonic movement. Elastic reboundtheory elasticrebound theelasticreboundtheoryisanexplanationforhow energyisspreadduringearthquakes. The elasticrebound theory of earthquakes bulletin of the department of geology, calif university of california. From an examination of the displacement of the ground surface which accompanied the 1906 earthquake, henry fielding reid. Seismicityand statistical propertiesofearthquakes 19 2. The theory involves the slow build up of elastic strain due to largescale stresses in the crust on either side of a locked fault i. The elastic rebound theory states that pressure builds in rocks on opposite sides of a fault until. This theory is known as the elastic rebound theory. First, sudden outset of earthquake in a certain point cannot be due to chronic continental drift in large scale. In geology, the elastic rebound theory was the first theory to satisfactorily explain earthquakes.
Reid gave, for example, a crude forecast of the next great earthquake near san francisco. Elastic rebound theory is directly related to earthquakes. Elastic rebound theory is one of the central ideas to the mechanics of earthquakes and was originally proposed by reid 1910 following the 1906 san francisco earthquake on the san andreas fault. According to the elastic rebound theory, rocks can bend elastically up to a point, until they finally break. The elastic rebound theory predicts that earthquakes can be generated only in the lithosphere.
In geology, the elastic rebound theory is a theory which tries to explain why earthquakes occur. Duponts plasticslip theory rocks store bending energy until they cannot store it any longer, then snap like a rubber ball. Terms in this set 11 how does the elastic rebound theory explain the occurrence of earthquakes. Earthquakes can be caused by faults, the motion of magma, and explosions e. If earthquakes obeyed the elastic rebound theory, large quakes should reset the seismic clock and there should be a gap before another big shock hit the same region.
However some of the characteristics of earthquakes can be explained by using a simple elastic rebound theory. Basically elastic rebound is the primary reason earthquakes even happen. In geology, the elasticrebound theory is an explanation for how energy is released during an earthquake. Terrifying earthquakes in modern history 21 photos when he and his colleagues thought about it, the concept of zipper faults could explain many of extremely confusing spots around the world. The theory also predicted, of course, that the place would be along tectonic earthquakes. Eventually, a preexisting weakness in the earthcalled a fault or a fault zonecan not resist the strain any longer and fails catastrophically. Alison, the main character, has a troubled past and feels alienated from the world. As the earths crust deforms, the rocks which span the opposing sides of a fault are subjected to shear stress. The process of ground being subjected to a growing force until it snaps or breaks is explained in a theory called the elastic rebound theory.
The following animation shows a birds eye view of a country road that cuts through an orchard. However, based on studies in the tonga islands, earthquakes occur within the weak, ductile. According to the theory, a tectonic earthquake occurs when strains in rock masses have accumulated to a point where the. The point of the earths surface directly above the point where an earthquake occurs is called the. The occurrence of tectonic earthquakes can be explained by the theory of elastic rebound, first advanced by h. According to the elastic rebound hypothesis, most earthquakes are produced by the rapid release of energy stored in rock that has been subjected to great forces. Reids elastic rebound theory usgs earthquake hazard program. Most earthquakes are the result of the sudden elastic rebound of previously stored energy. Proposing the elastic rebound theory and basis for the. The largest earthquakes typically occur at plate boundaries. His theory of how earthquakes occur as a result of fracture of rocks along a fault is called elastic rebound theory.
As rocks on oppo site sides of a fault are subjected to force and shift. Previously it was thought that ruptures of the surface were the. The shock waves associated with nuclear weapons testing and other manmade. Follow report log in to add a comment to add a comment.
At some point the stresses become so great that the. Oblique view of a highly generalized animation of a subduction zone where an oceanic plate is subducting beneath a continental plate. The elastic rebound theory states that as a rock becomes stressed, it first. Earthquakes are vibrations of the earth caused by the sudden release of energy, usually along a fault. When fault stresses rise above a critical threshold for rupture1, the earth slips along the fault and an earthquake results. It is then only intuitive that any additional stress acting on a. According to elastic rebound theory, the blocks of rock on opposite side of a fault are forced in opposite directions by stress. The elastic rebound theory for the origin of earthquakes. Two earthquakes that differ in amplitude by factor of 10, differ by 1 unit magnitude, b. Nearly 95% of all earthquakes take place along one of the three types of plate boundaries. This video discusses the relationship between plate boundaries and earthquakes, deformation, elastic limit and rebound and the 3 kinds of faults earthquakes can happen in.
Nov 17, 20 the elastic rebound theory predicts that earthquakes can be generated only in the lithosphere. When the strength of the rock is exceeded, it suddenly breaks, releasing some of its stored energy as seismic waves. Due to the motion of the earths tectonic plates, the ground beneath our feet is always moving, just too slow and g. The energy released from seismic waves during an earthquake is 33 times more powerful for each unit rise, c. The model adopted in this paper assumes that a medium is permeated with a continuum field of defects and that a flow of defects describes an advanced state of deformation leading to fracturing. Why we need a new paradigm of earthquake occurrence. Elastic rebound theory rocks at the edges of tectonic plates are subject to tremendous forces resulting in intense deformation. The rate of this movement may be as little as a few inches.
The plane defined by the rupture is known as a fault, and the rock layers. The mechanisms and processes involved when earthquakes occur are extremely complex. This gradual accumulation and release of stress and strain is now referred to as the elastic rebound theory of earthquakes. The elastic rebound theory is an explanation for how energy is spread during earthquakes. Similarly, the crust of the earth can gradually store elastic stress that is released suddenly during an earthquake. The fault then rupturesthat is, it suddenly moves a comparatively large distance in a comparatively short amount of time. The elasticrebound theory of earthquakes harry fielding.
However, this theory has several fetal defects which fail to lead successful earthquake prediction. For most of the readers of this article, the gap theory, which hypothesizes that an earthquake is more probable over the segment of a given plate boundary where the last rupture occurred earlier, may be a classic well rooted in plate tectonics, and its proposed rejection by kagan and jackson 1991 on the basis of clustering found in the. However, based on studies done in the tonga islands, earthquakes occur within the weak, ductile asthenosphere. Reids elastic rebound theory usgs earthquake hazards. It is then only intuitive that any additional stress acting on a fault system that approaches failure could trigger. The point along a fault where an earthquake begins is called the. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. In geology, the elasticrebound theory is an explanation for how energy is released during an earthquake as the earths crust deforms, the rocks which span the opposing sides of a fault are subjected to shear stress. The process which produces a megathrust earthquake would generate a tsunami, not depicted here. When bending rocks fails, the stress energy releases in the form of the earthquake. It can be done in small groups or as a classroom demonstration, with students recording data. Dows recovery theory rocks recover violently when a mass collides with them.
Over time stresses in the earth build up often caused by the slow movements of tectonic plates. In elastic rebound theory, what must occur to produce an earthquake. How is the elastic rebound theory related to earthquakes. Slowly they deform, until their internal rigidity is exceeded. Dec 05, 2010 the two main answers to how earthquakes happen is. The elastic rebound theory of earthquakes bulletin of the department of geology, calif university of california. This explains how energy is released during earthquakes. In ancient times earthquakes were thought to be caused by restless gods or giant creatures slumbering beneath the earth. San andreas fault, 1906 earthquake, elastic rebound. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The scale independent inclusion theory of rock failure developed in part i is applied to the problem of crustal earthquakes and, in particular, to the problem of premonitory phenomena reported to precede such earthquakes.
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