ObjectiveAgendaDo-NowHomework *Describe the effects of Plate Tectonics (EEn 2.1.1) Do-now Earthquakes guided notes Brainpop Earthquake disaster activity Midterm study guide Where do Earthquakes happen? Midterm study guide is due Monday Midterm exam is Wed, 11/5 Honors paper due 11/14 October 31 st, 2014

Earthquakes Dr. R. B. Schultz

Global Earthquake Locations

What is an Earthquake? Shaking of earth due to movement of rocks along a fault. Types of Seismic Waves Primary or "P" Waves: Primary waves, arrive first. Can travel through solids and liquids. Secondary or "S" Waves: Secondary waves. Slower than P waves Cannot travel through liquids L wave (long wave, surface wave, love wave): The L wave causes the damage and will be the last at the epicenter. Travels the slowest; last to be recorded

Primary or “P” Wave Secondary or “S” Wave

Earthquakes

Types of Seismographs

Seismogram Printout

Definitions Focus  the location within the earth where underground rock moves and sends out earthquake waves Epicenter  is the point on the Earth's surface that is directly above the focus. Most damage is done here.

Focus and Epicenter of Earthquake

3 types of Stress Compression  Pushes rock together (makes a reverse/ thrust fault) Tension  Pulls the rock apart (makes a normal fault) Shear  twists the rock (makes a strike- slip fault)

3 Kinds of faults Reverse Faults  compression stress in exerted on the rock from opposite sides. Moves up and down Normal Faults  tension stress pulls rock from opposite sides. Moves up and down Strike-Slip Fault (also known as a Transform fault)  Caused by shear stress. Grinds past each other.

Three Types of Faults

What Causes Earthquakes? A.Movement along faults — Occurs when the energy exceeds the friction holding the sides of the fault together and is suddenly _________________. B.Movement of magma (volcanic) C.Volcanic eruptions

Seismo world Fill out!

Why are the earthquake waves the strongest at the epicenter?

Magnitude The amount of energy released during an earthquake. Moment Magnitude Scale (replaces the Richter Scale) Logarithmic Scale Represented by using 1 to 10 Compares the energy released by different earthquakes on the basis of the area of the geological fault that ruptured in the quake. Richter Scale Numerical scale Represented by using 1 to 10. Measures energy waves given off by earthquakes. Mercalli Scale used to express damage

Moment Magnitude Scale

Richter Scale

Mercalli Scale

Hazards associated with Quakes Shaking Ground displacement (ground moving up/down/side to side) Tsunamis- Series of water waves generated by an earthquake (or underwater landslides) Liquefaction- unconsolidated materials (soil) that are water saturated may turn into a fluid causing damage Seiche- water that sloshes back and forth in a small body of water Fires

Determining the location of an earthquake 1.Time between the arrival of the P and S waves to the seismograph station is converted to a distance 2.A circle with a radius that equals the distance is drawn around the station. 3.Two stations can narrow down the location to two places where the two circles intersect. 4.You need 3 seismographic stations to find the epicenter of an earthquake.

Triangulation of 3 stations to locate earthquake epicenter

Another Way….Travel-Time Graph (not time travel!) 1. A travel-time graph shows… The average travel time of P and S waves for different distances 2. One can calculate the distance to the epicenter using the arrival times of the p and s waves.

Travel-Time Curves Suppose the waves recorded on a seismogram at Station A are farther apart than they are at Station B… The epicenter is farther from Station A.

Different speeds of P and S waves First, look at an example at the times for P and S wave travel. How long does it take for a P wave to travel 5000 km? An S wave? P wave – 8 minutes S wave – 14 minutes and 40 seconds

Finding distance from seismogram The earlier seismogram has an S-P travel time difference of 5 minutes. So, we must find the place on the graph where the difference between the P and S curves is 5 minutes and find the corresponding distance, as shown here. Start by using your y axis to measure 5 minutes, as shown. Measure 5 minutes here Then move it to where it fits exactly between the lines. And read the distance here as 2900 km.

Your task Preparedness Activity Work on Midterm study guide-due Monday –Midterm is on Wed.