Earthquakes 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:An earthquake can cause:

-buildings and bridges to collapse

-disrupt utility supply lines-trigger landslides, avalanches,

flash floods, fires, and huge destructive ocean waves.

EarthquakesEarthquakes

Earthquakes

Residence in Los Gatos moved off Residence in Los Gatos moved off its foundation its foundation

Hector Mine surface rupture Hector Mine surface rupture

Earthquake Location MapEarthquake Location MapNinety 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 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 TypesPlate Boundary Types

• Convergent Boundaries

• Divergent Boundaries

• Transform Faults

Convergent BoundaryConvergent Boundary

• Mountain Building

Convergent BoundaryConvergent Boundary

• Subduction Zone

Divergent BoundaryDivergent Boundary

• Sea Floor Spreading

Transform FaultTransform Fault

• Plates move past each other.

Most Recent Utah EarthquakeMost Recent Utah EarthquakeJuly 11, 2003 – Near HuntsvilleJuly 11, 2003 – Near Huntsville

Seismicity of the U.S 1975-1995.Seismicity of the U.S 1975-1995.

Earthquake Measurements Earthquake Measurements

• Magnitude – Richter ScaleEnergy released during the earthquake

• Intensity – Mercalli Scale Damage or loss of life caused by the

earthquake

Richter ScaleRichter Scale

• 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.

• Invented by Charles F. Richter in 1934

Richter Scale MeasurementRichter Scale Measurement

• Richter Scale is calculated using a seismograph

SeismometerSeismometer

• 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 EarthquakesLocating Earthquakes

Richter ScaleRichter 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 scaleMercalli 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 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.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.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 TerminologyEarthquake 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 WavesTypes of Earthquake Waves

• Primary or P waves

• Secondary or S waves

• Surface or L waves

Body wavesBody waves

Surface wavesSurface waves

TsunamiTsunami

• Tsunamigenic is referring to those earthquakes, commonly along major subduction-zone plate boundaries such as those bordering the Pacific Ocean, that can generate tsunamis.

Destructive EarthquakesDestructive Earthquakes• Date Location Deaths Mag Comments

• January 23, 1556 China, Shansi 830,000 • July 27, 1976 China, Tangshan 255,000* 8.0 Estimated

death toll (official) as high as 655,000.• 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 200,000 8.6 Major

fractures, landslides.• March 23, 893+ Iran, Ardabil 150,000• September 1, 1923 Japan, Kwanto 143,000 8.3 Great Tokyo

fire.• October 5, 1948 USSR 110,000 7.3 (Turkmenistan,

Ashgabat)• December 28, 1908 Italy, Messina 70,000 7.5 Deaths from

100,000 earthquake and (estimated) tsunami.

Annual EarthquakesAnnual 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 1900's• 1. Chile 1960 05 22 9.5 Mw• 2. Prince William Sound, Alaska 1964 03 28 9.2 Mw• 3. Andrean of Islands, Aleutian Islands 1957 03 09 9.1 Mw• 4. Kamchatka 1952 11 04 9.0 Mw• 5. Off the Coast of Ecuador 1906 01 31 8.8 Mw• 6. Rat Islands, Aleutian Islands 1965 02 04 8.7 Mw• 7. India_China Border 1950 08 15 8.6 Mw• 8. Kamchatka 1923 02 03 8.5 Mw• 9. Banda Sea, Indonesia 1938 02 01 8.5 Mw• 10. Kuril Islands 1963 10 13 8.5 Mw

Remember Remember

It’s not It’s not

“ If ” “ If ”

But But

When!!!!!!!When!!!!!!!

““Have a nice day”Have a nice day”