The earthquake

In the preceding chronicles, those developments that supported the atomic idea were stressed. On the other hand. Maxwell s development of electromagnetic theory, an un-dulatory theory, is an important link in the chain. Another fact of great consequence is that in the latter part of the 19th century a great amount of experimental work was devoted to the study of spectra. 

Today it is difiicult to imagine the complacency of the physicist of 1890. Classical physics was a house in order mechanics, thermodynamics, kinetic theory, optics, and electromagnetic theory were the main foundations—an imposing display. By choosing tools from the appropriate discipline any problem could be solved. Of course, there were one or two problems that were giving some trouble, but everyone was confident that these would soon yield under the usual attack. There were two parts in this house of physics the corpuscular and the undulatory, or the domain of the particle and the domain of the wave. Matter was corpuscular, light was undulatory, and that was that. The joint between matter and light did not seem very smooth. 

The year 1913 marks a major climax in the history of science. The application of Planck s quantum hypothesis to blackbody radiation, and later by Einstein to the photoelectric effect, had met with disbelief and in some quarters even with scorn. Bohr s application to the theory of the hydrogen atom compelled belief and worked a revolution in thought. In the following ten years this new knowledge was quickly assimilated and applied with spectacular success to the interpretation of spectra and chemical periodicity. 

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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. 

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,... 

Figure 14.12(b) represents an actual time history (accelerogram) of the earthquake that occun ed in Chamoli, India, on 29 March 1999. It had apeak ground acceleration of nearly 0,15 g and a predominant frequency of about 2 Hz. 

It is also accepted that after such an event, the ruptured earth surfaces may try to settle down again. It is possible that during the course of such a realignment there may still remain pockets of energy between the two plates until they finally settle. These may develop into releases of stresses once again, leading to occasional tremors or earthquakes even for. several days tifter a major earthquake or volcanic eruption. The earthquakes in Turkey are examples where two equally devastating earthquakes occurred between September and November 1999. 

Seismie analysis is carried out for all important engineering structures such as dams, bridges and nuclear power plants. For regions where these are to be located the likely expectations of an earthquake as well as the extent of its magnitude must be assessed on the basis of the seismic history and the earthquake records of the region (Figures 14.12 to Figure 14.16). Based on these and other factors such as soil stratification, site dependent response spectra are determined. These are the RRS for equipment mounted... 

Magnitude of the earthquake, hypoceniral distance and soil stratification. 

An RRS is normally constructed for several levels of critical dampings as illustrated in Figure 14.13. The most appropriate of these is then chosen for the purpose of testing. Any of the above response spectra can be developed into a time history of the earthquake, similar to that in Figure 14,12(b),... 

Small or moderate thickness of soil Where there is some soil, ground displacement will be greater and seismic waves will pass through the soil. There may be some settlement of the structure due to soil compaction. While the structure will now be less subject to seismic forces, this may prove to be a worse case, as in addition to the structure being subject to almost the full intensity of the earthquake, there may also be settlement of the soil, which may result in settlement of the structure and cause it to collapse or develop cracks. 

Greater depth of soil when there is a deep layer of soil, the intensity of the earthquake will reduce. The greater the distance from the focal point, the smaller will be ground movements. In such cases it is seen that the settlement of the soil below the structure may be negligible as it would have already settled by the time the shock reached the surface, and hence damage to the structure would be reduced. 

Now that it is possible to establish test facilities in a laboratory to simulate the time history of an earthquake seismic tests are conducted by creating the ground movements in the test object. Other methods, such as by analysis or by combined analysis and testing, are also available. Refer to IEEE 344 and lEC 60980 for more details. For this purpose a shake table, able to simulate the required seismic conditions (RRS) is developed on which the test object is mounted and its performance observed under the required shock conditions. Since it is not easy to create such conditions in a laboratory, there are only a few of these facilities available. The better equipped laboratories are in Japan, the USA, the UK, Greece, Germany, India and China. In India the Earthquake Engineering Department (EQD) of the University of Roorkee (UoR) is equipped with these facilities. 

Fig. 9-4 Photograph of landslides (soil avalanches) that occurred following earthquakes in Panama on July 17,1976, near Jaque. In the background is a bay of the Pacific Ocean. The effects of this earthquake are described by Garwood et al. (1979), who estimated that about 42 km (about 10%) of the region near the epicenter of the earthquake was devegetated. The bedrock is mostly island-arc basalts and andesites. (Photography by N. C. Garwood.)...

The term (ae/g) is called the seismic constant Ce, and is a function of the natural period of vibration of the vessel and the severity of the earthquake. Values of the seismic constant have been determined empirically from studies of the damage caused by earthquakes, and are available for those geographical locations which are subject to earthquake activity. Values for sites in the United States, and procedures for determining the stresses induced in tall columns are given by Megyesy (2001), Escoe (1994) and Moss (2003). 

After the Athens earthquake in 1981 there was a marked increase in deaths due to heart attacks over a period of five days after the quake on the day of the earthquake in Los Angeles, there was an increase in heart attacks. In the first few days after the Iraqi missile attacks on Israel in 1991, there was a sharp increase in heart attacks in Israel compared with control periods. The psychological stress caused by these sudden disasters could have raised the blood fatty acid levels above the safe level in some subjects which could have increased the risk of a heart attack. 

The next day, I phoned in my needs to Richmond and was assured that when I got there the volume I needed would be immediately available at noon as I had asked. I made two errors in navigation in my search for the Richmond Agricultural Field Station, and located the Earthquake Research Library first. But I was met with total courtesy and was supplied with improved directions. It turned out that the field library had a Xerox machine than needed nickels, and I happened to have a pile of nickels. And I now have my recipe for the nitration of piperonal firmly in hand. But I also got a feeling that the priorities of those who needed to use reference libraries might be in conflict with the priorities of those who controlled these reference libraries. 

After this wind will come an earthquake that will overthrow those things which the wind has left, and will make all flat. But be sure that you do not fall off. The earthquake being past, there will follow a fire that will consume the earthly rubbish and disclose the treasure. But as yet you cannot see it. 

Dona remained slumped in misery. He had expected Hyacinth, but never Enrico. As members of the inner circle of government, the two men must have known each other and worked together for decades. Apart from any personal loss, the scandal of a great minister confessing to the murder of his own distinguished father was going to shake the city harder than the earthquake of 1511. 

Fires directly caused by the earthquake were six in number, one of which, in a laboratory at the University of California, was started by a fire of leaking toluene ignited either by an electric furnace or from the reaction of metallic sodium. The total damage amounted to 24,000 dollars. 

Five minutes after the outbreak of the earthquake,the veneer ceiling turned black, generated white smoke at several points, and soon caught fire. The fire services office together with the local fire defense brigade made effort to stop the fire, but, because the hydraulic pressure was only half of the normal, the fire could only be extinguished two hours later by using three water pools. 

Tanks in the Whittier area suffered great damage from the seismic wave (Fig.2.2). A witness who tried to escape by car crossed the tank yard about one minute after the start of the earthquake when the top of a 53,500bbl capacity gasoline tank broke and the contents blew out. Fearful that the car would catch fire, he left the car and ran to the exit. Just as he left the tank yard, the seismic wave came and the explosion occurred 4 3. ... 

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