Earthquakes - GEOL 114 The Earth's Dynamic Interior Lecture...

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GEOL 114 The Earth's Dynamic Interior Lecture Notes (Copyright © 2006 by Jeffrey S. Barker) 15. Earthquakes Clearly, earthquakes are devastating phenomena. No one would choose to go through an experience like that shown to the right as a result of the Kobe earthquake of January 1995. Nevertheless, we have seen that earthquakes are an unavoidable result of Plate Tectonics. Also we have seen that earthquakes can happen just about anywhere in the world. So, we will spend some time discussing earthquake processes, hazards, current and future research. Intensity The first earthquake scientifically studied was on Nov 1, 1755 in Lisbon, Portugal. It was All Saints Day, so most people were in the churches and cathedrals when they collapsed. Over 60,000 people were killed, not only from the earthquake, but also the ensuing fire and tsunami. In 1857, the first maps of damage patterns were made for an earthquake near Naples, Italy. Lines connecting areas of equal damage (or intensity of shaking) were called isoseismals. In the 1880s intensity scales were defined using Roman numerals (I - X) to describe increasing degrees of damage. In 1931 the Modified Mercalli Intensity (MMI) Scale was developed, appropriate for the building practices and social conditions in California (updated in 1956). The Modified Mercalli Intensity Scale goes from I - XII. Abridged Modified Mercalli Intensity Scale Intensity Description I People do not feel any Earth movement. II A few people might notice movement if they are at rest and/or on the upper floors of tall buildings. GEOL 114 1 15. Earthquakes
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Intensity Description III Many people indoors feel movement. Hanging objects swing back and forth. People outdoors might not realize that an earthquake is occurring. IV Most people indoors feel movement. Hanging objects swing. Dishes, windows, and doors rattle. The earthquake feels like a heavy truck hitting the walls. A few people outdoors may feel movement. Parked cars rock. V Almost everyone feels movement. Sleeping people are awakened. Doors swing open or close. Dishes are broken. Pictures on the wall move. Small objects move or are turned over. Trees might shake. Liquids might spill out of open containers. VI Everyone feels movement. People have trouble walking. Objects fall from shelves. Pictures fall off walls. Furniture moves. Plaster in walls might crack. Trees and bushes shake. Damage is slight in poorly built buildings. No structural damage. VII People have difficulty standing. Drivers feel their cars shaking. Some furniture breaks. Loose bricks fall from buildings. Damage is slight to moderate in well-built buildings; considerable in poorly built buildings. VIII Drivers have trouble steering. Houses that are not bolted down might shift on their foundations. Tall structures such as towers and chimneys might twist and fall. Well-built buildings suffer slight damage. Poorly built structures suffer severe damage. Tree branches break. Hillsides might crack if the ground is wet. Water
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This note was uploaded on 11/02/2010 for the course GEOLOGY 111 taught by Professor Howardr.naslund during the Spring '10 term at Binghamton University.

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Earthquakes - GEOL 114 The Earth's Dynamic Interior Lecture...

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