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What is an earthquake?
An earthquake is the trembling or shaking of the ground that we feel when pieces of the earth's crust push against each other hard enough to overcome friction andi begin to slip . Because these pieces are so huge, the size of cities or states or countries, the energy released when they slip a little can be enough to shake apart buildings and other structures. This is especially so if the structure wasn't built or re-built (retrofit) specifically to withstand violent shaking.
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How long do earthquakes last?
Typically, just seconds. In a medium to large earth quake, the ground shakes strongly about 10 to 30 seconds. After the first slip, the earth readjusts causing more earthquakes called after shocks. These can occur weeks or months later.
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Is there "earthquake weather"?
No. Earthquakes happen all year round, night and day, rainy or clear, hot or cold. They have no weather or seasonal preference.
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Do small earthquakes release enough energy to prevent major earthquakes?
No. They're too small. It would take approximately 810,000 quakes of magnitude 3 to release as much energy as one quake of magnitude 7.
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Where is the safest place to be in an earthquake?
Out in the open where nothing can fall on you. People don't get hurt by earthquakes. People get hurt by buildings, or pieces of buildings falling on them. If you're inside a building, get under a strong piece of furniture, a desk or a table, something to keep between you and falling debris or breaking glass. If you are outside the building move away from the building as quickly as possible. More on this subject in our Safety and Preparedness area.
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Can earthquakes be predicted?
Not with precison. Where we have a lot of historical data and/or very high quality instrumental input we can say with a high degree of certainty that an earthquake of a certain minimum magnitude will occur in a certain area at some time within a range of years or decades, but that's as close as we can come at present. The Chinese who invented the first mechanical device to detect ground shaking in 132 A.D. have correctly predicted some earthquakes enabling cities to evacuate before the quake. But they have also suffered major earthquakes they didn't predict and predicted other earthquakes that didn't happen.
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What is the Richter Scale?
The Richter Scale is used to decribe the size of earthquakes by measuring earthquake waves on an instrument called a seismograph. When the size of an earthquake is described in terms of "magnitude" the number referred to is in units of the Richter Scale. The Scale is not divided evenly, though. Each unit level on the scale means an increase of approximately 30 times the energy release and 10 times the ground movement of the previous unit level.
Here are some examples of Richter magnitudes:
Magnitude 0 ... One pound of dynamite exploding.
Magnitude 1 ... A full size pick-up truck running into the side of Fort Knox at 75 MPH.... about the same as a suitcase full of dynamite..
Magnitude 3 ... The smallest earthquake most people can feel... about the same as 1000 full size pick-up trucks running into the side of Fort Knox at 75 MPH at the same time.
Magnitude 5... 30, 000 TONS of dynamite exploding... 1000 times stronger than the smallest quake most people can feel.
Magnitude 7... The Loma Prieta earthquake (7.1)... 1000 times stronger than 30,000 tons of dynamite.
Magnitude 8... 1906 San Francisco earthquake (8.3)... about as powerful as 30 Loma Prieta earthquakes.
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When was the largest earthquake in the united States seismographed?
1964, Prince William Sound, Alaska, magnitude 9.2.
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Where was the largest earthquake in the world seismographed?
Chile, magnitude 9.5, 1960.
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When was the largest earthquake in the state of Connecticut recorded?
1791, in Middlesex County on the Connecticut River northeast of New Haven. The magnitude is unknown, the first seismographs weren't installed in the U.S. until 1887, but the historical record states that stone walls were shaken down, chimneys toppled from houses and a crack opened up in the earth several meters long. This quake was reported to have been felt in Boston and New York City.
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