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An Earthquake.... with shocking characteristics – teacher’s sheet 1 Yesterday, there was an earthquake which was felt by millions of people around the world. The focus of the earthquake was deep under the 5 islands of the Carribean; however, strangely enough, the tremors were felt more strongly in other, faraway places such as Australia and Canada than in the islands directly above the 10 point from which the shockwaves originated. Scientists in seismological laboratories around the world are already analysing information that 15 has been recorded by sensitive tremor-detecting equipment. There are many peculiar and surprising things about this odd and unexpected seismic event: 20 First, the strange distribution around the world of the strength with which the shockwaves have been felt on the surface of the Earth; most of the energy (approximately 70%) released 25 from the rock-fracture was transported by the shockwaves at a depth below ground-level at which normally only 15% of the total energy released is transported. 30 Secondly, the orientation of the the fault plane along which the fracture in the rock occured has been shown to be horizontal – normally the fracture plane of an earthquake is 35 inclined at between twenty and eighty-five percent. Also, the focus of the earthquake was unusually deep - approximately 320 kilometres below the Carribean 40 Sea, some 60 kilometres North of the Los Roques archipelago, owned by Venezuela. This factor disproves the theory, that was until now widely accepted, that directly 45 beneath the Earth’s crust, which has a maximum thickness of 50 kilometres is a layer of molten rock, 500 to 600 kilometres thick, since when an earthquake occurs, it is 50 caused by a sudden fracture in the rock at the focus of the earthquake, and hence, the rock at that point must clearly be solid. The Task: Students must work out by inference the words that have been chopped off the end of each line in the text. Earth’s surface X * X Fault plane * * Maximum amount of energy transported in these directions. X - Focus of the earthquake The diagram above shows the directions in which pressure is exerted in relation to the fault plane. Parts of the ground on opposite sides of the fault plane experience forces in the opposite direction to each other, as shown by the differently shaded parts of the diagram. An Earthquake.... with shocking characteristics – students’ sheet 1 Yesterday, there was an earthquake which was felt by millions of people around the world. The focus of the earthquake was deep under the 5 islands of the Carribean; however, strangely enough, the tremors were felt more strongly in other, faraway places such as Australia and Canada than in the islands directly above the 10 point from which the shockwaves originated. Scientists in seismological laboratories around the world are already analysing information that 15 has been recorded by sensitive tremor-detecting equipment. There are many peculiar and surprising things about this odd and unexpected seismic event: 20 First, the strange distribution around the world of the strength with which the shockwaves have been felt on the surface of the Earth; most of the energy (approximately 70%) released 25 from the rock-fracture was transported by the shockwaves at a depth below ground-level at which normally only 15% of the total energy released is transported. 30 Secondly, the orientation of the the fault plane along which the fracture in the rock occured has been shown to be horizontal – normally the fracture plane of an earthquake is 35 inclined at between twenty and eighty-five percent. Also, the focus of the earthquake was unusually deep - approximately 320 kilometres below the Carribean 40 Sea, some 60 kilometres North of the Los Roques archipelago, owned by Venezuela. This factor disproves the theory, that was until now widely accepted, that directly 45 beneath the Earth’s crust, which has a maximum thickness of 50 kilometres is a layer of molten rock, 500 to 600 kilometres thick, since when an earthquake occurs, it is 50 caused by a sudden fracture in the rock at the focus of the earthquake, and hence, the rock at that point must clearly be solid. Earth’s surface X * X Fault plane * * Maximum amount of energy transported in these directions. X - Focus of the earthquake Edge of the column