Earthquakes name earthquakes are the, rolling or sudden of the earth’s surface. Earthquakes happen along " lines" in the earth’s. Earthquakes can be felt over large areas although they usually last less than minute



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EARTHQUAKES

NAME____________________________________

Earthquakes are the ___________, rolling or sudden _______________ of the earth’s surface. Earthquakes happen along "____________ lines" in the earth’s ____________. Earthquakes can be felt over large areas although they usually last less than ____________ minute.

Earthquakes cannot be _______________ -- although scientists _______________ working on it!

______________ of the time, you will ____________ an earthquake by the gentle ______________ of the ground. You may notice ______________ plants swaying or objects wobbling on _____________. Sometimes you may hear a ________________ rumbling noise or feel a ______________ jolt. A survivor of the _____________ earthquake in San Francisco said the sensation was like _______________ a bicycle down a long flight of stairs.

The intensity of an __________________ can be measured. One measurement is called the Richter _________________. Earthquakes below ______________ on the Richter scale usually do not cause damage, and earthquakes below _____________ usually can’t be felt. Earthquakes over _____________ on the scale can cause damage. A magnitude ______________ earthquake is considered strong and a magnitude _________ is a major earthquake. The Northridge Earthquake, which hit Southern California in 1994, was magnitude ___________.

Earthquakes often occur when _____________ plate collide

What happens when ______________ collide? It depends how the plates are ____________ when they _______________:

When two plates collide _____________-on, they __________ each other up and _________________ mountains. That's how the Himalayas and other great mountain ranges (including the Rockies, long ago) were _____________.

When one plate dives ________________ another plate, it creates a subduction ______________ as the diving plate is crushed and melted. This process often creates ________________ as the magma (molten rock)

rises up to ___________ surface.

When two _______________ slide past each other, they create a ___________fault, like the San Andreas fault.

Earthquakes can happen in ______________ of these situations. Despite the powerful forces driving _______________ movement, the plates themselves spend much of the time locked in place by the friction of the plates rubbing against each other. Eventually, however, they _________________ up so much pressure that the plates ___________ snap forward. Then the ground can shift a few feet—or a few dozen!

Shock ___________from that sudden motion ________ out in all directions, creating an _____________________.
Two great plates, the ____________ and the North American, meet in ______________. The Pacific Plate is moving north, creating a transform fault (the San Andreas and related faults) __________ the last 20 million years the Pacific Plate has slid about ____________ miles north. If it keeps moving as predicted, San Francisco will ______________ neighbors with Seattle in _________________ million years!
Because the _________________ Andreas fault curves around Los Angeles, and then _____________ into the Pacific in northern California, the two plates ______________ slide smoothly against each other. Instead, the complex ______________ of plate movement have fractured the _____________ and created _________ of smaller fault lines.

Seismologists have been ___________ California's faults for decades. They now say that the ___________ Francisco Bay Area has a ___________ chance of a major earthquake before ___________. This forecast is based on years of ____________ of the many faults in the area. The map shows the probability of a _____________ from each of these faults.
The rate of ____________ earthquakes in the San Francisco Bay region abruptly __________after the Great 1906 Earthquake. The San Andreas Fault ______________ so much over such a great length in that quake that the strain was ____________ on most faults throughout the region. Strain has been slowly _____________ up again.
Earthquakes can also occur _______________ plates, although plate-boundary earthquakes are ____________ more common. Less than __________ percent of all earthquakes occur within ___________ interiors. The New Madrid earthquakes of 1811-________ and the 1886 Charleston earthquake occurred within the _______________ American plate.

Earthquakes: Facts and ______________

Fiction: Earthquakes usually happen in the ____________.

Fact: Earthquakes happen in ____________ the day and the night. There is ________ pattern. Fiction: There is such a thing as "earthquake ________."

Fact: There is __________connection between earthquakes and weather. Remember, earthquakes happen _________ in the earth, far away from the weather!

Fiction: Earthquakes are _________ the increase.
Fact: It may seem like we’re having more earthquakes because there are __________ reporting stations, but the truth is we’re not.

Fiction: We can _____________ earthquakes from happening.

Fact: No. You can protect _____________ by doing things to secure buildings, like your home, but earthquakes can’t be prevented -- or predicted.
The point beneath the Earth's surface where the rocks ___________ and move is called the _____________of the earthquake. The focus is the underground point of origin of an earthquake. Directly above the focus, on the Earth's surface, is the ______________.

Earthquake waves are known as ___________ waves. There are three main types of seismic waves. Each type of wave has a characteristic ____________ and manner of _____________.
P waves are push-__________ waves. As P waves travel, they _______________ rock particles into the particles ahead of them, thus compressing the particles. The ____________ particles then bounce back. They ______________ the particles behind them that are being pushed forward. The particles move _____________ and forth in the direction the ________________ are moving.

Secondary Waves

Seismic __________________ that do not travel through the Earth as fast as P waves do are secondary waves, or ____________ waves. S waves arrive at a given point after _______________ waves do. S waves travel through solids but not through liquids and gases.


Surface Waves

The slowest-moving seismic waves are called ___________ waves, or L waves. L waves arrive at a given point after primary and secondary waves do. L waves originate at the epicenter. ___________ waves travel along the surface of the earth, rather than ____________ into the earth. Although they are the ____________ of all the earthquake waves, L waves usually cause ____________ damage than P or S wave.

http://www.stemnet.nf.ca/cite/seismograph.gif
This is an _________________ of a seismograph, an instrument used to _______________the energy released by an earthquake. When the needle is ___________________ by the motion of the earth, it leaves a wavy line.
http://www.stemnet.nf.ca/cite/wave_animation.gif


___________________primary waves followed by ________________ secondary waves move outward in concentric circles from the epicenter of an earthquake off British Columbia and Washington State.
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