Earthquake Safety 6 th Grade Earth Science

Earthquake Safety

6

th

Grade Earth Science

Earthquake Risk

Earthquakes are likely wherever plate movement stores energy in the rock along faults.

Geologists can determine earthquake risk by locating where faults are active and where past earthquakes have occurred.

In the United States, the risk is highest along the Pacific coast in California, Washington, and Alaska.

In California, the Pacific plate and North American plate meet along the San Andreas fault.

In Washington,

subduction

of the Juan de Fuca plate beneath the North American plate causes earthquakes.

In Alaska,

subduction

of the Pacific plate causes earthquakes.

Why are earthquakes felt over a larger area near Kentucky?

In the Central and Eastern United States, earthquakes are felt over a broader area than comparable-size quakes in the Western United States because of differences in geology. Although only of magnitude 6, the earthquake that occurred near Saint Louis in 1895 affected a larger area than the 1994 magnitude 6.7 Northridge, California, quake, which caused $40 billion in damage and economic losses and killed 67 people. A repeat of the 1895 earthquake could prove disastrous for the Midwest, where structures are not as earthquake resistant as those in California.

Eastern United States

The eastern United States generally is low risk for earthquakes, because the area is not near any plate boundaries.

But, some of the most powerful quakes have occurred in this area.

New Madrid 1811-1812

Scientist think this is because of the continental plate forming most of North America is under stress.

This stress could disturb faults that lie beneath thick layers of rock and soil.

How Earthquakes cause Damage

The

shaking

produced by seismic waves can trigger landslides or avalanches.

Shaking

can damage or destroy buildings, bridges, and fracture gas or water lines.

S waves and surface waves, with their side-to- side and up-and-down movement, can cause severe damage near the epicenter.

The types of rock and soil determine where and how much the ground shakes.

The most violent shaking may occur kilometers away from the epicenter.

Loose soil shakes more than solid rock.

A house built on sandy soil will shake more than a house built on rock.

Living on soft soil is bad because it amplifies earthquake motions.  This swimming pool was crushed during the 1971 San Fernando earthquake.  Water flooded into the house where all four occupants were thrown out of bed by the severe shaking.  Two people were knocked unconscious.

How Earthquakes cause damage

Liquefaction

occurs when an earthquake’s violent shaking suddenly turns loose, soft soil into liquid mud.

Liquefaction

is likely to happen where the soil is full of moisture.

As the ground gives way buildings sink and fall apart.

Aftershock

is an earthquake that occurs after the larger earthquake in the same area. It can strike hours, days, or even months later.

Tsunamis

When an earthquake moves the ocean floor, plate movement causes the ocean floor to rise slightly and push water out of the way.

The water displaced by the earthquake may form a large wave called a tsunamis.

A

tsunamis

spreads out from an earthquake’s epicenter and speeds across the ocean.

In the open ocean the height of the wave is low.

As it approaches shallow water, the wave grows into a mountain of water.

Tsunamis

means harbor wave in Japanese.

Tsunamis

http://www.uwgb.edu/dutchs/EarthSC-102VisualsIndex.HTM

Formation of a tsunami

http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

Tsunami Warning System

http://isu.indstate.edu/jspeer/Earth&Sky/EarthCh11.ppt

Largest Tsunami

Alaskan Panhandle in 1958

Fairweather

Fault caused an 8.3 magnitude earthquakes along with a massive landslide. Created a wave that was 1720 feet high.

10 Worst tsunami

1. Dec. 26, 2004 –Sumatra-Indonesia

9.1-9.3 magnitude earthquake, known as the Indian ocean

tsunami.

Dec 8

th

- 2012

7.3 Earthquake causes 1 meter high tsunami

Earthquake in Japan 2011

In March of last year, the Daiichi plant at Fukushima was the scene of the worst nuclear disaster since the Chernobyl tragedy in 1986. A 9.0-magnitude quake triggered a massive tsunami, causing damage to the plant that led to multiple meltdowns. Over 15,000 people died and more than 3,200 people went missing. 

On December 26, 2004, a massive earthquake occurred under the sea off the coast of Sumatra Island, Indonesia. The magnitude of the earthquake was 9.0 on the Richter scale, making it the third biggest earthquake in the past 100 years. Shortly after the quake, the shores of surrounding countries were hit by a big tsunami, which was over 10 meters high in some places. The earthquake and tsunami took the lives of more than 280,000 people, and they destroyed many buildings and roads.

The speed of a tsunami is about 80 km per hour when the water is 50 m deep, about 250

kph

at 500 m, and about 800

kph

- as fast as a jet airplane - at 5,000 m. A tsunami slows down as it nears shore, but it would still be impossible to escape if you were to start running away only after seeing it.

A tsunami can suddenly grow very tall when it enters narrow places like an inlet or a gulf, and sometimes it will rush up the shore. The tallest known tsunami to ever hit Japan's Honshu Island was 38.3 m tall, and the world record is the 520 m tsunami that was observed in Alaska.

A continental plate is dragged down and bent by an oceanic plate.

The continental plate cannot bend any more and snaps back, pushing the seawater up.

The seawater spreads in all directions as a tsunami and reaches land, sometimes hours later.

Steps to Earthquake Safety

The main danger is from falling objects and flying glass.

You should

drop, cover, and hold

.

If you are indoors, get under a desk or table.

Stay away from the outside of a building, and cover your head and neck with your arms.

Avoid windows, mirrors, wall hangings, and furniture that could fall over.

If you are outside, move to an open area like a playground or field.

Avoid vehicles, power lines, trees, and buildings.

Earthquake safety

To reduce earthquake damage, new buildings must be made stronger and more flexible.

Walls need to be reinforced.

To combat liquefaction, new homes built on soft ground need to be anchored to solid rock below.

Bridges and overpasses can also be anchored to solid rock below existing soft soil.

A

base-isolated

building is designed to reduce the amount of energy that reaches the building during an earthquake.

A

base-isolated

building rests on shock-absorbing rubber pads or springs.

During a quake the building moves gently back and forth without violent shaking.

Utilities

Earthquakes can cause fire and flooding when gas pipes and water mains break.

Flexible joints can be installed in gas and water lines to keep them from breaking.

Automatic shut-off valves can be installed on these lines to cut off gas and water flow.