Earthquakes An earthquake is a sudden rapid shaking of the earth. They are caused by the breaking and shifting of the rock beneath the earth s surface. Often found in conjunction with Plate tectonic boundaries.
An earthquake can cause: -buildings and bridges to collapse -disrupt utility supply lines -trigger landslides, avalanches, flash floods, fires, and huge destructive ocean waves.
Earthquakes Earthquakes
Damage in Haiti
Damage from Earthquake in Japan
Earthquake in Turkey
Hector Mine surface rupture
Earthquake Location Map Ninety percent of the world's earthquakes occur in specific areas that are the boundaries of the Earth's major crustal plates. Shown on the map are the epicenter locations of earthquakes of magnitude 4.5 or greater that occurred from 1978 through 1987.
Ring of Fire The "Ring of Fire", also called the Circum-Pacific belt, is the zone of earthquakes surrounding the Pacific Ocean--about 90% of the world's earthquakes occur there.
Plate Boundary Types Convergent Boundaries Divergent Boundaries Transform Faults
Convergent Boundary Mountain Building
Convergent Boundary Subduction Zone
Divergent Boundary Sea Floor Spreading
Transform Fault Plates move past each other.
Recent Utah Quakes
Earthquakes that occurred in one weeks time
Earthquakes with a magnitude of 3.5 or greater. 1974-2003
Earthquake Measurements Magnitude Richter Scale Energy released during the earthquake Intensity Mercalli Scale Damage or loss of life caused by the earthquake
Richter Scale Invented by Charles F. Richter in 1934 The Richter magnitudes are based on a logarithmic scale (base 10). What this means is that for each whole number you go up on the Richter scale, the amplitude of the ground motion recorded by a seismograph goes up ten times.
Richter Scale Measurement Richter Scale is calculated using a seismograph
Seismometer A seismograph, or seismometer, is an instrument used to detect and record earthquakes. Generally, it consists of a mass attached to a fixed base. During an earthquake, the base moves and the mass does not.
Locating Earthquakes
Richter Scale 3.5-5.4 Often felt, but rarely causes damage. Under 6.0 At most slight damage to well-designed buildings. Can cause major damage to poorly constructed buildings over small regions. 6.1-6.9 Can be destructive in areas up to about 100 kilometers across where people live. 7.0-7.9 Major earthquake. Can cause serious damage over larger areas. 8 or greater Great earthquake. Can cause serious damage in areas several hundred kilometers across.
Mercalli scale Invented by Giuseppe Mercalli in 1902, This scale uses the observations of the people who experienced the earthquake to estimate its intensity.
Mercalli Scale I. Not felt except by a very few under especially favorable circumstances. II. Felt only by a few persons at rest, especially on upper floors of buildings. Delicately suspended objects may swing. III. Felt quite noticeably indoors, especially on upper floors of buildings, but many people do not recognize it as an earthquake. Standing automobiles may rock slightly. Vibration like passing of truck. Duration estimated. IV. During the day felt indoors by many, outdoors by few. At night some awakened. Dishes, windows, doors disturbed; walls make creaking sound. Sensation like heavy truck striking building. Standing automobiles rocked noticeably.
Mercalli Scale Cont. V. Felt by nearly everyone, many awakened. Some dishes, windows, and so on broken; cracked plaster in a few places; unstable objects overturned. Disturbances of trees, poles, and other tall objects sometimes noticed. Pendulum clocks may stop. VI. Felt by all, many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster and damaged chimneys. Damage slight. VII. Everybody runs outdoors. Damage negligible in buildings of good design and construction; slight to moderate in well built ordinary structures; considerable in poorly built or badly designed structures; some chimneys broken. Noticed by persons driving cars. VIII. Damage slight in specially designed structures; considerable in ordinary substantial buildings with partial collapse; great in poorly built structures. Panel walls thrown out of frame structures. Fall of chimneys, factory stack, columns, monuments, walls.heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well water. Persons driving cars disturbed.
Mercalli Scale Cont. IX. Damage considerable in specially designed structures; well designed frame structures thrown out of plumb; great in substantial buildings, with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously. Underground pipes broken. X. Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked. Rails bent. Landslides considerable from river banks and steep slopes. Shifted sand and mud. Water splashed, slopped over banks. XI. Few, if any, (masonry) structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipelines completely out of service Earth slumps and land slips in soft ground. Rails bent greatly. XII. Damage total. Waves seen on ground surface. Lines of sight and level distorted. Objects thrown into the air.
Earthquake Terminology Epicenter area on the earths surface directly above the focus or hypocenter Fault area of two surfaces of rock move passed one another Focus actual location of the earthquake Hypocenter same as the focus
Types of Earthquake Waves Primary or P waves The faster of these body waves is called the primary or P wave. Its motion is the same as that of a sound wave in that, as it spreads out, it alternately pushes (compresses) and pulls (dilates) the rock. These P waves are able to travel through both solid rock, such as granite mountains, and liquid material, such as volcanic magma or the water of the oceans.
The slower wave through the body of rock is called the secondary or S wave. As an S wave propagates, it shears the rock sideways at right angles to the direction of travel. If a liquid is sheared sideways or twisted, it will not spring back, hence S waves cannot propagate in the liquid parts of the earth, such as oceans and lakes.
The actual speed of P and S seismic waves depends on the density and elastic properties of the rocks and soil through which they pass. In most earthquakes, the P waves are felt first. The effect is similar to a sonic boom that bumps and rattles windows..
Some seconds later, the S waves arrive with their up-and-down and side-to-side motion, shaking the ground surface vertically and horizontally. This is the wave motion that is so damaging to structures
Surface waves travel more slowly than body waves (P and S); and of the two surface waves, Love waves generally travel faster than Rayleigh waves. Love waves (do not propagate through water) can effect surface water only insofar as the sides of lakes and ocean bays pushing water sideways like the sides of a vibrating tank, whereas Rayleigh waves, becasuse
of their vertical component of their motion can affect the bodies of water such as lakes.
Body waves
Surface waves
Tsunami Tsunamigenic is referring to those earthquakes, commonly along major subductionzone plate boundaries such as those bordering the Pacific Ocean, that can generate tsunamis.
Destructive Earthquakes Date Location Deaths Mag Comments January 23, 1556 China, Shansi 830,000 July 27, 1976 China, Tangshan 255,000* 8.0 death toll (official) as high as 655,000. Estimated August 9, 1138 Syria, Aleppo 230,000 May 22, 1927 China, near Xining 200,000 8.3 Large fractures. December 22, 856+ Iran, Damghan 200,000 December 16, 1920 China, Gansu fractures, landslides. 200,000 8.6 Major March 23, 893+ Iran, Ardabil 150,000 September 1, 1923 Japan, Kwanto 143,000 8.3 Great Tokyo fire. October 5, 1948 Ashgabat) USSR 110,000 7.3 (Turkmenistan, December 28, 1908 Italy, Messina 70,000 7.5 Deaths from 100,000 earthquake and (estimated) tsunami.
Annual Earthquakes Magnitude Average Annually Great 8 and higher 1 Major 7 _ 7.9 18 Strong 6 _ 6.9 120 Moderate 5 _ 5.9 800 Light 4 _ 4.9 6,200 (estimated) Minor 3 _ 3.9 49,000 (estimated) Very Minor 2 _ 3: about 1,000 per day 1 _ 2: about 8,000 per day
Earthquakes 1. Chile 1960 9.5 Mw 2. Prince William Sound, Alaska 1964 9.2 Mw 3. Northern Sumatra 2004 9.1 Mw 4. Japan 2011 9.0 Mw 5. Russia 1952 9.0 Mw 6. Chile 2010 8.8 Mw 7. Ecuador 1906 8.8 Mw 8. Rat Island, Alaska 1965 8.7 Mw 9. Indonesia 2005 8.6 Mw 10. Tibet 1950 8.6 Mw