Earthquake

Earthquakes consist of violent horizontal and vertical movement of Earth s surface resulting from relative movements of tectonic plates. Huge masses of rock in the plates may be locked relative to each other for as long as centuries, then suddenly move along fault lines. This movement and the elastic rebound of rocks that occur as a result cause the earth to shake, often violently and with catastrophic damage. 

The fact that earthquakes may sometimes be preceded by geochemical anomalies was discovered at about the same time in Japan (Okabe, 1956) and the then USSR (Fursov, 1968). Earthquake prediction studies in Russia, Japan and China include extensive geochemical measurements. Chinese geochemical data are reported to have contributed, at least partly, to the successful prediction of several strong earthquakes (Allen et al., 1975). In contrast, the Earthquake Hazards Reduction Program in the United States emphasises mainly geophysical data. 

Numerous other examples of gas flux related to earthquakes have been reported, for example, by Kartsev et al. (1959), Fursov et al. (1968), Elinson et al. (1970), Sokolov (1971b), Eremeev (1972) Ovchinnikov et al. (1972), Zorkin (1977b), Melvin et al. (1978), Wakita et al. (1978, 1980), Barsukov et al. (1979), Borodzich et al. (1979), 

Mamyrin (1979), King (1980b), Reimer (1980), Shapiro et al. (1981, 1982), Mooney (1982) and Pirkle and Jones (1983). Particularly intriguing examples have been published by Antropov (1981) of atmospheric methane flux related to petroleum deposits (Fig.5-14) and seismic shock (Figs. 5-15 and 5-16). These measurements were made with adsorption-type gas lasers one type makes point measurements of the sample in an adsorption tube (lskatel-2) the other (Luch) measures the specific gas adsorption along a path length (1-100 m). 

6 earthquake that rocked Oklahoma on November 5, 2011, was caused by fracking. The following section provides a basic understanding of earthquakes and their causes. 

It s been raining a lot, or very hot—it must be earthquake weather  

FICTION Many people believe that earthquakes are more common in certain kinds of weather. In fact, no correlation with weather has been found. Earthquakes begin many kilometers (miles) below the region affected by surface weather. People tend to notice earthquakes that fit the pattern and forget the ones that don t. Also, every region of the world has a story about earthquake weather, but the type of weather is whatever they had for their most memorable earthquake. 

It is obvious that a more profound investigation of some of the phenomena mentioned requires methods from areas of knowledge outside the scope of this book. On the other hand, some of the assessments needed may be performed with methods of plant safety, which are discussed in the sections mentioned above. 

The design of plants against earthquakes requires, as a mle, the determination of response spectra of the object under consideration (building, vessel etc.) to the excitation caused by the movements from the earthquake. A detailed treatment is beyond the present scope. Instead a simple assessment of the loads on the support columns of a spherical tank is presented based on [24]. However, it goes beyond the treatment given there by explicitly accounting for stochastic parameters. 

Earthquakes are generally characterized by indicating acceleration, velocity and ground displacement. Comprehensive methods for assessing earthquake effects account for all three parameters. In what follows only the horizontal acceleration is addressed. 

According to [29] the annual number of earthquakes of magnitude greater M on the Richter scale can be described by 

For the lower Rhine basin, one of Germany s seismically most active zones [28], a = 4.6, B = 1.8 and M ,ax = 6.9 are to be used. M ,ax represents the maximum expected earthquake magnitude. As can be seen from Eq. (4.35) the expected frequency of earthquakes of any magnitude (M = 0) in the lower Rhine basin is given by 

In the case of intraplate regions, a model for diffuse seismicity should be developed to complement the extrapolation of historical strong motion data. The methods described in Ref [9] are recommended. Hazard category 3 facilities may be assessed using national seismic codes confirmed by local evidence. 

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It is rare to be able to observe elastic deformations (which occur for instance during earthquakes) since by definition an elastic deformation does not leave any record. However, many subsurface or surface features are related to the other two modes of deformation. The composition of the material, confining pressure, rate of deformation and temperature determine which type of deformation will be initiated. 

Acoustic foremnners appear as ground vibrations in the range from 0,1 to 50 Hz with the amplitudes from 10 to 10 m (dynamic range is 160 dB). To control these parameters a large number of earthquake-shock recorders based on different principle of operation are manufactured... 

Electromagnetic earthquake forerunners show themselves like the electromagnetic phenomena, including electromagnetic emission (EME) in a radio frequency range. This emission caused by collective exiting of the set of local mechano-electrical transformers (MET). The excitation mechanism inside the crust is determined by the fact that elastic tension ranges up to the threshold level within the source area. 

Electrical forerunners may be found out as the result of electrical field potential between two points (electrotelluric field on the earth surface) measurement. Usually the background potential is 10 mV and during the earthquake it equals to 70 mV. 

When the earthquake is coming the radioactive radiation background is increasing and this is a typical sample of radiation forerunner. 

The P-radiation was shown to cause the positive deviation from the background level (approx. 3 times) before the earthquake. 

For geological and geochemical earthquake forerunners the variations of radon content in underground waters are used. The radon content dispersion systematically increases before the earthquake. 

Foam rheology has been a challenging area of research of interest for the yield behavior and stick-slip flow behavior (see the review by Kraynik [229]). Recent studies by Durian and co-workers combine simulations [230] and a dynamic light scattering technique suited to turbid systems [231], diffusing wave spectroscopy (DWS), to characterize coarsening and shear-induced rearrangements in foams. The dynamics follow stick-slip behavior similar to that found in earthquake faults and friction (see Section XU-2D). 

Regulations include guidelines on geologic conditions. Of special interest is the stabiUty of the geology against faulting, volcanic action, and earthquakes. The repository is to be located in an arid region, where the water table is quite low. The host rock is to have a suitable porosity and a low hydrauhc conductivity. 

Dynamic Ejfects Design must provide for impact (hydraulic shock, etc.), wind (exposed piping), earthquake (see ANSI A58.1), discharge reactions, and vibrations (of piping arrangement and support). 

Part AD This part contains requirements for the design of vessels. The rules of Division 2 are based on the maximum-shear theoiy of failure for stress failure and yielding. Higher stresses are permitted when wind or earthquake loads are considered. Any rules for determining the need for fatigue analysis are given here. 

Additional information on newer aspects on the behaviour of the earth during an earthquake has been... 

Our present discussions relate only to the laboratory testing of safety-related secondary systems, as are employed in critical areas such as areas of emergency power supply and reactor power control supply etc. of a nuclear power plant (NPP) according to IEEE 344 and lEC 60980. There are other codes also but IEEE 344 is referred to more commonly. Basically, all such codes are meant for an NPP but they can be applied to other critical applications or installations that are prone to earthquakes. 

Random vibrations, such as tho.se caused by an earthquake, cause shocks and ground movements and are termed seismic disturbances. Shocks and turbulence caused by a heavy sea, landslides and volcanic eruptions are also examples of shocks that may cause vibrations and result in tremors, not necessarily earthquakes. Nevertheless, they may require design considerations similar to those for an earthquake, depending upon the applieation (e.g. naval applications, hydro projects, dams and bridges). 

The outer shell of the earth, consisting of the upper mantle and the crust (Figure I4. lO), is formed of a number of rigid plates. These plates are 20 in number and are shown in Figure 14.1 I. Of these, six or seven are major plates, as can be seen in the map. The edges of these plates define their boundaries and the arrows indicate the direction of their movement. These plates contain the continents, oceans and mountains. They almost float on the partially molten rock and metal of the mantle. The outer shell, known as the lithosphere, is about 70 to 1,50 km thick. It has already moved great distances below the etirth s surface, ever since the earth was formed and is believed to be in slow and continuous motion all the time. The plates slide on the molten mantle and move about lO to 100 mm a year in the direction shown by the arrows. The movement of plates is believed to be the cause of continental drifts, the formation of ocean basins and mountains and also the consequent earthquakes and volcanic eruptions. 

When the plates slide past each other, they may cause stresses at the edges of the crust. The stresses may build up and at some stage exceed the resilience of the earth s crust and cause a fault, i.e.. cause the crust to rupture and shift. When this occurs, it causes an earthquake in the form of violent motion of the earth s surface and/or large sea waves. Major earthquakes occur because of this phenomenon. 

The magnitude of shocks and vibrations caused by an earthquake is the measure of energy released (E) at the focal point in the form of seismic waves. It is measured on a Richter scale. An American seismologist called... 

M = magnitude of the earthquake A = maximum amplitude, as recorded by the Wood Anderson seismograph in microns at a distance of 100 km from the epicentre. 

Since the distance of the instrument from the epicentre will usually not be exactly 100 km, a distance correction must be applied to obtain the magnitude of the earthquake, defined as,... 

This definition of the magnitude of earthquake is used for the records of Wood Anderson type torsion seismograph. This has a dampening equal to 80% of the critical natural, period of 0.8 second and a magnification of 2800. 

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