Earthquakes n A shaking of the Earth’s crust caused by a release of energy and results from the movement of the lithospheric plates n Most destructive of the natural disasters, affects largest area

Causes of Earthquakes n Eruption of volcanoes n underground caverns collapsing n meteorites n Stress builds between lithospheric plates-stress > friction forces, plates move- Earthquake- plates return to same shape, but different locations Elastic-rebound theory

Depth of Earthquakes Depends on the type of boundary Spreading centers, sliding boundary shallow quakes (30 km deep) Subduction, deep quakes (700 km) Focus - point on fault plane where first movement occurs Epicenter - point on surface directly above focus

Earthquake Waves Three kinds of wave motion 1. Compressional-back and forth wave motion causes rock material to be squeezed and stretched P-wave) Primary waves n 1st to arrive at seismograph station n can travel through any material

2)Shear waves causes rock material to move side to side or right angles to direction the wave is traveling n S waves or secondary waves can not travel through liquids or gases n P and S waves are body waves, they travel thru body of Earth n L waves = P & S waves combine at surface called surface waves

Speed of Waves Depends on type and nature of rock Velocity of waves is greatest when rock is rigid and dense P waves travel twice as fast as S waves in any material L waves travel slower than both P and S waves

Seismographs n The instrument that detects and records earthquake waves n Several types record different motions n Drum moves, not pen (Inertia) n First recorded wave is P wave n Larger the deflection, larger quake Record sheet is called seismogram

Finding Distance and Location P wave arrives first, then S wave Greater the difference in arrival time the further away the earthquake Use time-travel graph to find distance from epicenter~ 1 station Need 3 stations to determine location of epicenter~~ triangulation

Richter Scale of Magnitude Each magnitude number represents an earthquake with 32 times more energy released Difference of two, 1000 X stronger Amplitude of earthquake wave is 10 X greater per magnitude

Magnitude (Richter Scale) n What are the Magnitude classes? Great = M > 8 Major = 7 < M < 7.9 Strong = 6 < M < 6.9 Moderate = 5 < M < 5.9 Light = 4 < M < 4.9 Minor = 3 < M < 3.9

Seismic Moment tells total energy 1}Takes into account amount of movement along fault plane 2} size of fault plane 1906 San Francisco and 1964 Alaskan Earthquakes both had magnitudes of 8.3 on Richter SF=7.9 and AK=9.2 seismic moment

12 levels of Modified Mercalli Intensity. I. Not felt except by a very few under especially favorable conditions. II. Felt only by a few persons at rest, especially on upper floors of buildings. III. Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.

IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably. V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop. VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken. VIII. Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. IX. Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.

X. Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent. XI. Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly. XII. Damage total. Lines of sight and level are distorted. Objects thrown into the air.

Earthquake Damage n Ground shaking ~ causes Earth to vibrate and buildings to shake up and down and sideways. n Foundation failure ~ results from ground shake: causes soil to settle and liquefy

Earthquake Risk & Prediction Forecasts: 1) When, 2) Where, 3) Magnitude Seismic Gap Method Fore shocks, elevation increase, tilting, decrease in electrical resistance, radon in wells increase, P waves slow, porosity less, premonition of animals

Earth’s Interior and Waves Information about Earth’s interior has come from seismic waves Change in velocity at 2900 km depth shows where the mantle meets core Outer core liquid, S wave velocity 0 Boundary of crust/mantle named (Moho) Mohorovicic Discontinuity 32 km below continents, 8 km /ocean

Shadow Zone n Waves sent in all directions from focus of earthquake, but not all seismograph stations receive info n Broad belt on opposite side of Earth from quake do not receive P or S waves because of the outer core being liquid n Area called shadow zone

Examples of Earthquakes Alaska caused by subduction California, continuous sliding boundary ( San Andreas Fault) Missouri- zones of weakness in craton a midplate earthquake

Loma Prieta DATE: Oct. 17, 1989 TIME: 5:04 PM MAGNITUDE: 7.1 DURATION: 15 seconds DEATHS: 62 INJURIES: 3,757 PROPERTY DAMAGE: >$6 Billion COMMENTS: rupture of 40 km fault stretch (25 mi. [40 km] segment of San Andreas fault SW of San Jose slipped ~ 7 ft]; SF Bay Bridge unusable for 1 month; 18,306 homes damaged; 2,575 business damaged; 12,053 people displaced

San Francisco 1906 DATE: April 18, 1906 TIME: 5:12 am MAGNITUDE: 8.25 DURATION: 40 seconds DEATHS: 700-2,500 people (debated) COMMENTS: 400 km fault segment released; San Andreas fault slipped as much as 15 ft along 270 mi. (434 km) segment from south of San Jose to northwestward to Cape Mendocino

Largest Earthquake in North Carolina Near Waynesville, North Carolina :39 UTC, 5.20Mfa, MM VII Tops of chimneys were thrown to the ground; windowpanes were broken in many houses; and people rushed into the streets at Waynesville. At Sevierville, Tennessee about 70 kilometers northwest of Waynesville, bricks were shaken from chimneys. In Wear's Cove, about 16 kilometers southwest of Sevierville, the flow of water in springs increased and in places water became muddy. Minor damage was reported in western Tennessee at Athens, Knoxville, Maryville, Morristown, and Newport, Tennessee; at Tryon, North Carolina; and at Bristol, Virginia. Also reported felt in Alabama, Georgia, Kentucky, South Carolina, and West Virginia.

10 Largest Earthquakes in Contiguous US 1.) New Madrid, Missouri ) Fort Tejon, California ) Owens Valley, California ) Imperial Valley, California ) New Madrid, Missouri ) San Francisco, California ) Pleasant Valley, Nevada ) New Madrid, Missouri ) Landers, California Ms 10.) Kern County, California

On the basis of the large area of damage (600,000 square kilometers), the widespread area of perceptibility (5,000,000 square kilometers), and the complex physiographic changes that occurred, the Mississippi River valley earthquakes of rank as some of the largest in the United States since its settlement by Europeans. The area of strong shaking associated with these shocks is two to three times larger than that of the 1964 Alaska earthquake and 10 times larger than that of the 1906 San Francisco earthquake. The first and second earthquakes occurred in Arkansas (December 16, two shocks - Mfa 7.2, MSn 8.5 and Mfa 7.0, MSn 8.0) and the third and fourth in Missouri (January 23, 1812, Mfa 7.1, MSn 8.4; and February 7, 1812, Mfa 7.4, MSn 8.8). Otto Nuttli, however, has postulated another strong earthquake in Arkansas on December 16 at 18:00 UTC (MSn 8.0). This would make a total of five earthquakes of magnitude MSn 8.0 or higher occurring in the period December 16, 1811 through February 7, 1812.

10 Largest Earthquakes in US 1.) Prince William Sound, Alaska ) Andreanof Islands, Alaska ) Rat Islands, Alaska ) East of Shumagin Islands, Alaska ) Lituya Bay, Alaska ) Yakutat Bay, Alaska ) Near Cape Yakataga, Alaska ) Andreanof Islands, Alaska ) New Madrid, Missouri ) Fort Tejon, California

Trees up to 24 inches in diameter and between 88 and 101 feet above sea level were broken and splintered by the surge wave generated by an underwater landslide in Port Valdez, Prince William Sound.

10 Largest Earthquakes in the World Since ) Chile 05/22/ Mw1.) Chile 05/22/ Mw 38.2 S 72.6 W *8.3 Richter 2.) Alaska 03/28/ Mw2.) Alaska 03/28/ Mw 61.1 N W *8.3 R 3.) Russia 11/04/ Mw3.) Russia 11/04/ Mw N E 4.) Ecuador 01/31/ Mw4.) Ecuador 01/31/ Mw 1.0 N 81.5 W 5.) Alaska 03/09/ Mw5.) Alaska 03/09/ Mw 51.3 N W 6.) Kuril Islands 11/06/ Mw6.) Kuril Islands 11/06/ Mw 44.4 N E 7.) Alaska 02/04/ Mw7.) Alaska 02/04/ Mw 51.3 N E 8.) India 08/15/ Mw8.) India 08/15/ Mw 28.5 N 96.5 E 9.) Argentina 11/11/ Mw9.) Argentina 11/11/ Mw 28.5 S 70.0 W 10.) Indonesia 02/01/ Mw 5.25 S E

Chile 1960 May 22 19:11:14 UTC, 9.5 Mw More than 2,000 killed, 3,000 injured, 2,000,000 homeless, and $550 million damage in southern Chile; tsunami caused 61 deaths, $75 million damage in Hawaii; 138 deaths and $50 million damage in Japan; 32 dead and missing in the Philippines; and $500,000 damage to the west coast of the United States.

Tangshan, China-240,000 dead-2,000 in dormitory-7/27/76

Kobe