Earth quake!

Haiti Earthquake http://www.youtube.com/watch?v=fahz97JjeJ8&feature=channel Chile Earthquake http://www.youtube.com/watch?v=T7jaayXlm-M chile ppt.ppt

What is an Earthquake? A shake or vibration caused by the sudden breaking or sliding of rock in the Earth

Fault - Fracture (break) in rock where sliding occurs Where do they happen? Fault - Fracture (break) in rock where sliding occurs As tectonic plates move, they slide past other plates. At the edges they get stuck, but the plates keep moving. Eventually, the rock gives and a fault is formed.

Stress builds up between the two plates causing the crust to warp Elastic Rebound Stress builds up between the two plates causing the crust to warp An earthquake allows that energy to be released, and the plates return to their normal position (just shifted)

Stages of an Earthquake Inactivity (1 ½. Foreshock small quake that can occurs hours or days before a major earthquake) 2. Major Earthquake 3. Aftershock quakes that occur seconds to a year after a major earthquake

TYPES OF FAULTS Normal Fault Reverse Fault Strike Slip

-blocks of rock move apart -occur at divergent boundaries Normal Fault -blocks of rock move apart -occur at divergent boundaries

Reverse Fault -blocks of rock move towards each other -occur at convergent boundaries

-rocks move sideways past each other -occur at transform boundaries Strike Slip -rocks move sideways past each other -occur at transform boundaries

Earthquakes don’t always occur along a plate boundary… New Madrid Fault 1811-1812 3 Magnitude 8 Earthquakes

How do we measure earthquakes? Richter Scale -measures the height of seismic waves -each whole number is 10 times the seismic wave height -each whole number is 33 times more energy released

Richter Scale > 8 Total destruction About 1/year 7-7.9 Bad 18/year 6-6.9 Moderate -serious 120/year 5-5.9 Minor damage (felt by everyone) 800/year 4-4.9 Not felt by everyone 6,000/year < 3.9 Very small 1 million/year

Largest Earthquake on the Richter Scale: 9.5 Chile 1960

How do we measure earthquakes? 2. Mercalli Intensity Scale -the amount of damage an earthquake causes -scale of I - XII -very subjective -typically used for building codes

Mercalli Scale

How do we measure earthquakes? 3. Moment Magnitude Scale -combine how rigid the Earth is and the distance the Earth moves along the fault -scientists use this method the most

Predicting an Earthquake Short-term ‘Forecasting’ -hours to weeks -based on foreshocks *not always foreshocks

Predicting an Earthquake 2. Seismic Gap -areas along faults that have not had recent earthquakes -the more time without an earthquake, the greater the chance of an upcoming earthquake -larger earthquakes in the past -> more frequent earthquakes

Predicting an Earthquake 3. Recurrence Interval -earthquakes along a fault tend to have relatively constant recurrence patterns ex: San Andreas Fault -22 years between earthquakes of magnitude 5.5 or higher

Predicting an Earthquake 4. Anomalous Animal Behavior -dogs barking -chickens not laying eggs -rats perched on power lines *not considered scientific* though often evident

Deadliest Earthquakes 1. Shaanxi, China 1556 -830,000 casualties 2. Tangshan, China 1976 – 255,000 casualties 3. Gansu, China 1920 – 234,117 casualties 4. Haiti 2010 -233,000 casualties 5. Indian Ocean (Sumatra) 2004 – 230,210 casualties

Tangshan, China Animals also gave a warning that something was about to happen. One thousand chickens in Baiguantuan refused to eat and ran around excitedly chirping. Mice and yellow weasels were seen running around looking for a place to hide. In one household in the city of Tangshan, a goldfish began jumping wildly in its bowl. At 2 a.m. on July 28, shortly before the earthquake struck, the goldfish jumped out of its bowl. Once its owner had returned him to his bowl, the goldfish continued to jump out of its bowl until the earthquake hit. Chen Yong, et al, The Great Tangshan Earthquake of 1976: An Anatomy of Disaster (New York: Pergamon Press, 1988) 53.

Human Induced Earthquakes Several earthquakes have been caused because of human activity Examples: -building dams over inactive fault zones (e’quake and flooding) Nuclear Explosions (Nevada test site) *Some scientists think we should trigger ‘controlled quakes’ in California to reduce potential damage

As energy is released from an earthquake, it is distributed in waves Seismic Waves As energy is released from an earthquake, it is distributed in waves

Seismic Waves Body Waves Surface Waves Travel through the interior of the Earth Surface Waves Travel along the Earth’s surface

Body Waves P - Waves Primary Waves ‘pressure’ or ‘push – pull’ waves Travel fastest (few km/sec) Travel through all layers of Earth

Body Waves S – Waves Secondary Waves ‘shear’ or ‘shape’ waves Travel slightly slower than P waves Do not travel through liquids (outer core)

Body Waves

Make the ground ripple up and down Surface Waves R - Waves Rayleigh Waves Make the ground ripple up and down

Make the ground ripple side to side Surface Waves L - Waves Love Waves Make the ground ripple side to side

Seismograph An instrument that can record ground motion from an earthquake happening anywhere on Earth http://snowball.millersville.edu/~cws/seismic/current/Local_East-West/current.gif

Locating an Earthquake Focus Spot in the crust where the fault begins to slip *the deeper an earthquake, the less damage it causes at the surface* Epicenter Point on Earth’s surface directly above the focus

Locating an Earthquake How to find an epicenter -need 3 seismic stations to record the event -using the differences in arrival times, seismologists can determine the distance of the station to the epicenter

Triangulation When you connect the data from the 3 seismic stations, you will find the epicenter

Earthquake Aftermath Earthquakes themselves cause tremendous damage, but they also leave behind a path of destruction

Depending on the fault, giant cracks in the Earth can form 1. Ground Displacement Depending on the fault, giant cracks in the Earth can form Alaska 1964 Examples: 1964–Alaska– 12 m 1906–San Francisco– 7 m

2. Landslides Soil and Debris that is shaken during an earthquake may loosen and cause a landslide

3. Liquefaction Soil that has small amounts of water in it, will act as a liquid during an earthquake Ex: Kobe, Japan 1995

4. Tsunami Seismic sea wave Earthquakes that occur near oceans create massive waves which act as a wall of water Sumatra 2004

Destruction during an earthquake can cause large fires Tokyo - 1923 San Francisco - 1906