Earthquakes

EarthsStructure

Measuring

Predictions

The FilmWhere do

theyOccur?

Types of Faults

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Where do they occur?

Plate Tectonics Hazard Zones

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World Plate Boundaries

Divergent Plate

Boundaries

Transform plate

boundaries

Convergent plate

boundaries

Boundary Table

Click for a detailed map

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Boundary Type Plate Motion Regional Stress Main Fault Type Landform

Divergent Tension Normal Mid-Ocean Ridges

Transform Shear Strike-Slip Transverse Mntns

Convergent Compression Thrust Oceanic Trenches Volcanic Arcs

Table of Tectonic Plate Boundaries

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Divergent Plate Boundaries

where two plates move away from each other . Most of the world's divergent plate boundaries are on the ocean floor, in the form of mid-ocean spreading ridge. At divergent boundaries, the two plates are continually moving apart, heading in opposite directions away from each other.

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Divergent Illustration

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Divergent Plate Illustration

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Mid-Ocean spreading in the deep ocean basins where the plates move apart. As they separate, hot lava from the mantle rises between them. This lava gradually cools, contracts, and cracks, creating faults.

Most are shallow

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Transform Plate Illustration

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Where plate slide horizontally against each other. These can also be caused by soil liquefaction (where the soil acts like liquid)

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Transform Plate Boundaries

Where two plates move horizontally side-by-side in opposite directions. Transform plate boundaries are strike-slip faults. As the two plates slide next to each other, trying to move in opposite directions, there is much friction and stress between them. As a result, transform plate boundaries are zones of frequent earthquakes.

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Transform Plate

Illustration

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Convergent plate boundaries

Where two plates move toward each other and either collide with each other or one plate bends down and goes beneath the other.

Convergent plate

animation

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Convergent plate Illustration

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Called Sub-duction zones these comprise approximately 80% of major quakes. The famed Ring of Fire is included. One plate is thrust under another.

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Hazard ZoneAreas with frequent activity

The famed Ring of Fire

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Steps to Safety

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Our Violent HomeReview

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Make an earthquake preparedness kit!

Food, water, matches, flashlight, batteries, blankets and SHOES! All will be very hard to come by following a large earthquake!

Public Domain

Take action during an earthquake and remember to ‘Drop’, ‘Cover’ and ‘Hold On’. Move outside and away from buildings after the shaking.

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EARTHS STRUCTURE

Compositional Layers

Mechanical Layers

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Compositional Layers

Core

Mantle

Crust

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Mechanical Layers

Aesthenosphere

Lithosphere

Inner Core

Outer Core

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CrustThe outer layer of the Earth.

Continental crust is thick (25-50 km thick), low in density, and has an intermediate average composition.

Oceanic crust is thin (typically 5-10 km thick), higher in density, and has a mafic average composition

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MantleThe layer located above the Core and below the Crust it begins about 6 miles(10 km) below the oceanic crust and about 19 miles (30 km) below the continental crust. It is about 1,800 miles (2,900 km) thick and makes up about 80% of Earth’s total volume

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CoreAlthough we have no samples to look at Seismic waves suggest a very dense molten metallic core.

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Outer CoreIs scorching hot and electrically conductive liquid. It is where Earth’s magnetic field is generated.

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Lithospherewhich is a rigid layer that is broken up into tectonic plates and averages about 100 km (60 miles) thick.

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AesthenosphereThe layer beneath the lithosphere is the weak, soft Aesthenosphere, which is roughly 300 to 400 km thick

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Measuring Earthquakes

The Mercalli Scale

The Richter Scale

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The vibrations produced by earthquakes are detected, recorded, and measured by instruments called seismographs.  The line made by a seismograph, called a "seismogram," show the changing intensity of the vibrations by responding to the motion of the ground. From this scientists can determine the time, the epicenter, the focal depth, and the type of fault of an earthquake.

There are two main types of scales used in connection to Earthquakes. The Mercalli and the Richter.

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In 1935, Charles F. Richter devised a way to record quake activity by measuring the size of

the seismic waves caused by the shifting earth. These impressions are recorded on a device

known as a seismograph, and much can be told from this mechanism. This graph can measure the date and time, along with the exact central

location of these troubling disasters. They in turn, are then ranked in terms of severity on the world

famous

The Richter Scale

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One way to measure the strength of an earthquake is to use the Mercalli scale.

Invented by Giuseppe Mercalli in 1902, this scale uses the observations of the people who

experienced the earthquake to estimate its intensity.

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The Mercalli Scale

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Predictions

Scientist use past occurrences to determine the likelihood of quakes. Very little improvement has been made in the accuracy of these predictions over the last half century.

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Whose Fault is it?

The crustal plates are being deformed by stresses . The ground will first bend, then upon reaching a certain limit, breaks and “snaps” to a new position. There are a couple main types of faults which cause earthquakes.

Strike-Slip Fault

Dip-Slip Fault

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Strike-Slip FaultStrike-Slip faults move horizontally and form from Shear stress.

Strike-Slip Fault

Animation

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Dip-Slip FaultDip-Slip faults move vertically. One side moves up while the other moves down.

Dip-Slip Fault

Animation

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Strike-Slip FaultAnimation

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Dip-Slip FaultAnimation

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The Film

Devastation

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Quiz Question 1

Which of the below is a way to measure earthquake intensity?

The Mashall Scale The Mercury Scale The Mecalis Scale

REVIEW† Both the Mercalli and Richter scale are used to Measure Earthquakes.† Two plates moving horizontally (side by side) form Transform boundaries and are active areas for Earthquakes.

† Stop Drop and Cover! Is the safety motto for Quake preparedness† There are 3 major plate environments on Earth.

† The Lithosphere is 60 miles thick and is where most earthquakes occur.

REVIEW† Mid-Ocean Ridges form from Divergent boundaries.

† Nearly 80% of major Quakes form from Convergent boundaries

† The crust forms a thin outer layer on Earths surface.

† Earthquake prediction has not changed much over the last 20 years.

† What we have learned about the core is not from direct observation .† What we have learned about the core is not from direct observation .

Quiz Question 2

How many Major types of Plate environments exist?

2 4 3

Quiz Question 3

Prediction has evolved dramatically over the last 20 years.

TrueFalse

Quiz Question 4

This layer is on average 60 miles thick and most earthquakes occur

here.Inner Core Aesthenosphere Lithosphere

Quiz Question 5

When 2 plates move horizontally in opposite direction. This type of

boundary forms.Inoppositum Divergent Transform

Quiz Question 6

The Mid-Ocean ridges are formed by what type of boundary.

Convergent Ridgitum Divergent

Quiz Question 7

80% of major Earthquakes are caused by what type of boundary?

Diemuchium Transform Convergent

Quiz Question 8

Stop! Drop! Roll is the motto for Earthquake safety.

False True

Quiz Question 9

The Outer layer of the Earth structure is?

Outersphere Mantle Crust

Quiz Question 10

We have specific and direct observations of the Earth’s core.

TrueFalse

CreditsUSGS: Earthquake Center. (2007, March 20). Retrieved May 4, 2010, from United States Geologic Survey: http://earthquake.usgs.gov/earthquakes/

United States Geologic Survey. (n.d.). USGS Astrogeology Research Program. Retrieved May 4, 2010, from http://astrogeology.usgs.gov/

This Dynamic Earth: Developing the Theory. (2007, February 7). Retrieved May 4, 2010, from United States Geologic Survey: http://pubs.usgs.gov/gip/dynamic/developing.html

Dub Long Photo Library(2010)

Arranged By

Dub Longglong@nwacc.edu