Earthquakes What Is An Earthquake? Click here to find out

What is an earthquake? Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip Caused by volcanic or plate activity, The map above shows the distribution of earthquakes with magnitudes greater than 5.0 that occurred between 1965 and

Three Types of Faults Strike-Slip Normal Reverse Animation of fault movement

Normal fault Results in hanging wall slipping downward Hanging wall Foot wall animation

What type of fault? Hanging wall Foot wall normal

What causes earthquakes? Tectonic plates move past each other causing stress. Stress causes the rock to deform – What type of fault boundary is this? – What type of stress is shown? transform shearing

Strike – slip fault Rocks on either side of fault slip past each other sideways with little up or down motion - AnimationAnimation of strike-slip motion Occurs at a plate boundarytransform What type of stress is produced?

Fault rupture across road in western Kaynasli, right-lateral strike slip displacement was about 4.0 m (13 feet) at this location 0Reports/Duzce_1999/kaynasli1.htm

Reverse fault Pushes on the crust squeezing rock until it folds or breaks (like a trash compactor) = Occurs when plates are moving together Results in hanging wall slipping upward Hanging wall Foot wall animation

What type of fault? Hanging wall Foot wall reverse

What type of fault?

– 1. point inside the Earth where an earthquake begins – 2. point on Earth’s surface above focus where earthquake is FELT most strongly Epicenter Focus 1 2

How Seismographs Work the pendulum remains fixed as the ground moves beneath it A seismograph is an instrument used for recording the intensity and duration of an earthquake.

Earthquakes How are earthquakes measured? Seismograph machine Seismogram – seismic wave display record

Seismic Waves

Primary Waves (P Waves) A type of seismic wave that compresses and expands the ground The first wave to arrive at an earthquake

Secondary Waves (S Waves) A type of seismic wave that moves the ground up and down or side to side

Comparing Seismic Waves

Surface Waves Move along the Earth’s surface Produces motion in the upper crust – Motion can be up and down – Motion can be around – Motion can be back and forth Travel more slowly than S and P waves More destructive Animation of wave types

How do scientists calculate how far a location is from the epicenter of an earthquake? Scientists calculate the difference between arrival times of the P waves and S waves The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

Typical Seismogram start finish How much time elapsed between the arrival of the P wave (start) and the arrival of the S wave (finish)?

Locating Earthquakes

Locating Earthquakes

Now you are going to be seismologists and locate an Earthquake Go to: Click here to go to virtual earthquake site

National Geographic earthquake information

How are Earthquakes Measured? Richter Scale A logarithmic scale used to express the total amount of energy released ___________ of an earthquake. Its values typically fall between 0 and 9, with each increase of 1 representing a _________ increase in energy. magnitude 10-fold

How are Earthquakes Measured? Mercalli Intensity Scale Click for Interactive Demo Go to A scale of earthquake intensity based on ___________ and ranging from I (detectable only with instruments) to XII (causing almost total destruction). observed effects

Earthquake Waves & Earth’s Interior Seismic wave animation

Seismic Waves in the Earth Click here for animation

Tsunamis Click here for explanation of a tsunami

Formation of a tsunami PBS –tsunami animation a large ocean wave usually caused by an underwater earthquake or a volcanic explosion.

Click here for Japan helicopter view of tsunami With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage!

Tsunami Warning System

Review Questions 1. A large ocean wave usually caused by an underwater earthquake or a volcanic explosion. tsunami 2. Used to describe both a sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip earthquake

How are Earthquakes Measured? 3. Which one uses a logarithmic scale to express the total amount of energy released or magnitude of an earthquake. Richter Scale 4. Which uses a scale of earthquake intensity based on observed effects and ranging from I (detectable only with instruments) to XII (causing almost total destruction). Modified Mercalli Scale

What type of fault is shown by each picture? Normal Reverse Transverse or strike-slip

S-wave

Surface or Love waves

What type of fault? A Hanging wall has moved B Source: indiana.edu Reverse fault upward Strike –slip or transverse fault

– 1. point inside the Earth where an earthquake begins – 2. point on Earth’s surface above focus where earthquake is FELT most strongly Epicenter Focus 1 2

People walk along a damaged road in the province of Bohol on Tuesday, October 15, Do you think this was a major earthquake? Why or why not?

Yes, it was a major quake. It crumbled a number of buildings Such as this church 7.1 magnitude earthquake hit the Philippines

Earthquakes 5. __________ machine ____________ seismic wave display record Seismograph P-wave Surface S-wave Seismogram