Free Essays About Earthquakes

“It is a bitter and humiliating thing to see works, which have cost men so much time and labour, overthrown in one minute; yet compassion for the inhabitants is almost instantly forgotten…” Charles Darwin (on the ruin of Concepcion in Chile by an earthquake (Robinson 47)

People tremble when they hear the word; destruction, mayhem, and tragedy: all words that come to mind when “earthquake” is heard. They occur without warning and cause millions of dollars in destruction and numerous deaths. For these reasons and more, earthquakes are one of the most unpredictable and devastating occurrences Mother Nature dishes out.

Earthquakes usually occur without warning. There is a sudden slip in the earth’s crust, which makes the earth shake causing mass destruction to buildings and people in the surrounding areas. These areas in the earth’s crust are called faults. When the earth “faults” the ground bends to a certain limit until the point of breaking. When it finally snaps, it sends vibrations up to the earth’s surface where the earthquake occurs (USGS). There are two different types of waves during an earthquake, the P-wave and the S-wave. The P-wave is the primary wave that is the first wave to arrive, followed by the transverse, or S-waves, which arrive after (USGS). Quakes can last for short or long periods of time and are sometimes followed by aftershocks. They are tiny earthquakes that last for a few seconds after the bigger quake.

Charles F. Richter of the California Institute of Technology created the Richter magnitude scale in 1935 in order to compare the magnitudes of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs (USGS). The scale ranges from numbers zero through 10. A number such as 4.6 on the Richter scale would be considered a mediocre earthquake in seismologists’ minds while any number over six would be a large earthquake. Earthquakes under a two rating are not felt by people and are not recorded because no damage is done. Earthquakes of these magnitudes are likely to occur thousands of times a day while one of a ranking higher than eight will only occur once on average in the world each year. Earthquakes have also been measured in equivalence to weights of dynamite. For example, if an earthquake gets a reading between a 6.0 and a 7.0, it is the same as blowing up around 100,000 tons of dynamite (Nuhfer 39).

Earthquakes cause massive losses in money for the government when they strike. Buildings are knocked over, streets cracked, and there are many electrical problems that they have to deal with. It takes a lot of time for places to recover from the effects of earthquakes. A new Federal Emergency Management Agency report says that damages from U.S. earthquakes total about $ 4.4 billion a year. California alone accounts for $ 3.3 billion of the total (Fema 9). Another tragic loss we have when earthquakes come around is the loss of our family and friends. Thousands of people lose their lives without ever knowing what hit them. The most devastating quake in United States history is by far the one that “shook the world” in San Francisco in 1906. More than three thousand lives were taken on that day. The closest death toll to this in the United States was one hundred and fifteen, an earthquake that occurred in Long Beach, California in 1933 (USGS).

To try and reduce these loses of friends and relatives, there are steps to reduce hazards in the home. One example if you are in a high seismic-risk zone would be to strap or bolt all furniture to the floor or to the walls so that if an earthquake does occur, it will not harm anyone. Also, the frame should be checked periodically to make sure that it is all in tact. One final precaution would be to use plywood sheathing wherever needed, such as garage door areas, to strengthen the home so that less damage will occur (Bolt 228-29).

Most of the earthquakes that happen in the United States occur on the West Coast, especially in California. This is true because of one of the most famous fault lines in the world, the San Andreas Fault. This fault line stretches for over six hundred miles from the Imperial Valley in Southern California to Point Arena on the northern coast and then out to sea. To date more than twenty-five earthquakes have occurred in California. Most of these are because of the San Andreas Fault. And these are only the earthquakes that have been measured on the Richter scale.

The most recent damage an earthquake has done in the United States was on February 28, 2001 in the Puget Sound region of Washington State, called the Nisqually earthquake. The quake measured a 6.8 on the Richter scale and shook the earth for a good forty seconds. Even though it was a long earthquake, it was still one of the less damaging earthquakes of this magnitude in the United States. Immediately after the quake, 28 state bridge inspection teams examined about 500 state-owned bridges within a 73-mile radius of the epicenter. There was ”almost no structural damage,” said Weigel, Washington State Dept. of Transportation bridge engineer, to insure safety for motorists using the bridges (News Site). There was only one death contributed to it, a heart attack victim. The damage bill was nothing compared to other quakes. The bill totaled up to around two billion dollars. That may seem like a lot, but when compared to the earthquake in Northridge, California in 1994 it was pennies. This quake ranked at 6.7 on the scale and was the costliest earthquake the United Stated had ever had at forty billion dollars. The after shocks of this earthquake caused more damage than the entire Nisqually quake including its aftershocks, which did not reach above a 3.4 (SCEC). This quake was also different from other quakes, as the city of Santa Monica knows first hand. Parts of their coastal city, 21 kilometers south of Northridge and separated from it by a mountain range, had received shocks just as severe as those felt in Northridge (O’Hanlon). Scientists are still stunned about why this occurred, but attribute it to something of a magnifying glass of a rock in the earth’s surface that focused the quake to Santa Monica.

The Northridge quake, like all others, brought attention to the way that some buildings were structured. Although not much damage was done to some buildings due to the soft soil around it, others were hit hard. One of the more severely damaged buildings was the six-story Palmer Court Building, an un-reinforced masonry structure located in Seattle’s historic Pioneer Square district (Staff 10). Although damage to buildings is inevitable during an earthquake, improvements can still be made to buildings so that they do not end up like the Palmer Court Building. Every building, however moves somewhat during an earthquake, no matter its size. During the Loma Prieta Earthquake in San Francisco during the World Series, the seats were seen shaking back and forth along with the entire Candlestick Park. After a few moments of shaking, it regained its original position without much structural damage (Levy 94).

Although this is the most recent quake felt by the United States, one that occurred nearly a century ago will not soon be forgotten. The earthquake that occurred in San Francisco on April 18, 1906 ranks as one of the most significant earthquakes of all time (USGS). At around 5:00 in the morning, the northernmost 290 miles of the San Andreas Fault ruptured. Although the Richter scale was not around, it is believed to be one of the most powerful earthquakes to ever hit the United States. The city shook violently for almost a full minute. Fires blazed and approximately three thousand people were killed in this tragic event.

So is there anything anybody can do to prepare for another such disaster? There is really no way of knowing when the next earthquake will hit, but seismologists have several methods so that they can estimate approximately when another one will occur. By studying the amount of earthquakes and when they happen in a certain area, seismologist can then guess the probability of another one occurring in that area within a given time (CBC News). This will then give people the time to prepare themselves for another possible quake. Seismologists can also measure how much stress a certain region of the earth’s crust is under, and how quickly that stress is increasing. This will help them to determine if another quake is likely in that region, but it is a very difficult procedure and far from perfect because a lot of areas lack the equipment and data needed for this.

There is no way to stop earthquakes from shaking our earth. It is something that, unfortunately, we will have to deal with for the rest of our lives. Many scientists and seismologists are doing the best they can so that we can be better prepared for another earthquake when it hits. Until the time when we will be able to predict when they will strike comes, we will have to live knowing that at anytime an earthquake can come and shake up the earth as well as our lives.

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Earthquakes have plagued our lives for as long as people have inhabited the earth. These

dangerous acts of the earth have been the cause of many deaths in the past century. So

what can be done about these violent eruptions that take place nearly with out warning?

Predicting an earthquake until now has almost been technologically impossible. With

improvements in technology, lives have been saved and many more will. All that remains is

to research what takes place before, during, and after an earthquake. This has been done

for years to the point now that a successful earthquake prediction was made and was

accurate.

Earthquake, vibrations produced in the earth's crust when rocks in which elastic

strain has been building up suddenly rupture, and then rebound.The vibrations can range

from barely noticeable to catastrophically destructive. Six kinds of shock waves are

generated in the process. Two are classified as body waves—that is, they travel through

the earth's interior—and the other four are surface waves. The waves are further

differentiated by the kinds of motions they impart to rock particles. Primary or

compressional waves (P waves) send particles oscillating back and forth in the same

direction as the waves are traveling, whereas secondary or transverse shear waves (S

waves) impart vibrations perpendicular to their direction of travel. P waves always travel

at higher velocities than S waves, so whenever an earthquake occurs, P waves are the first

to arrive and to be recorded at geophysical research stations worldwide.

Earthquake waves were observed in this and other ways for centuries, but more

scientific theories as to the causes of quakes were not proposed until modern times. One

such concept was advanced in 1859 by the Irish engineer Robert Mallet. Perhaps drawing

on his knowledge of the strength and behavior of construction materials subjected to

strain, Mallet proposed that earthquakes occurred either by sudden flexure and constraint

of the elastic materials forming a portion of the earth's crust or by their giving way and

becoming fractured.

Later, in the 1870s, the English geologist John Milne devised a forerunner of today's

earthquake-recording device, or seismograph. A simple pendulum and needle suspended

above a smoked-glass plate, it was the first instrument to allow discrimination of primary

and secondary earthquake waves. The modern seismograph was invented in the early 20th

century by the Russian seismologist Prince Boris Golitzyn. His device, using a magnetic

pendulum suspended between the poles of an magnet. Most tectonic quakes occur at the

boundaries of these plates, in zones where one plate slides past another—as at the San

Andreas Fault in California, North America's most quake-prone area—or is subducted

(slides beneath the other plate). Subduction-zone quakes account for nearly half of the

world's destructive seismic events and 75 percent of the earth's seismic energy. They are

concentrated along the so-called Ring of Fire, a narrow band about 38,600 km long, that

coincides with the margins of the Pacific Ocean.

Seismologists have devised two scales of measurement to enable them to describe

earthquakes quantitatively. “One is the Richter scale—named after the American

seismologist Charles Francis Richter—which measures the energy released at the focus of

a quake. It is a logarithmic scale that runs from 1 to 9; a magnitude 7 quake is 10 times

more powerful than a magnitude 6 quake, 100 times more powerful than a magnitude 5

quake, 1000 times more powerful than a magnitude 4 quake, and so on.

The other scale, introduced at the turn of the 20th century by the Italian

seismologist Giuseppe Mercalli, measures the intensity of shaking with gradations from I

to XII. Because seismic surface effects diminish with distance from the focus of the

quake, the Mercalli rating assigned to the quake depends on the site of the measurement.

Intensity I on this scale is defined as an event felt by very few people, whereas intensity

XII is assigned to a catastrophic event that causes total destruction. Events of intensities II

to III are roughly equivalent to quakes of magnitude 3 to 4 on the Richter scale, and XI to

XII on the Mercalli scale can be correlated with magnitudes 8 to 9 on the Richter scale.

Attempts at predicting when and where earthquakes will occur have met with some

success in recent years. At present, China, Japan, Russia, and the U.S. are the countries

most actively supporting such research. In 1975 the Chinese predicted the magnitude 7.3

quake at Haicheng, evacuating 90,000 residents only two days before the quake destroyed

or damaged 90 percent of the city's buildings. One of the clues that led to this prediction

was a chain of low-magnitude tremors, called foreshocks, that had begun about five years

earlier in the area. Other potential clues being investigated are tilting or bulging of the

land surface and changes in the earth's magnetic field, in the water levels of wells, and

even in animal behavior. A new method under study in the U.S. involves measuring the

buildup of stress in the crust of the earth. On the basis of such measurements the U.S.

Geological Survey, in April 1985, predicted that an earthquake of magnitude 5.5 to 6

would occur on the San Andreas fault, near Parkfield, California, sometime before 1993.

Many unofficial predictions of earthquakes have also been made. In 1990 a zoologist, Dr.

Iben Browning, warned that a major quake would occur along the New Madrid fault

before the end of the year. Like most predictions of this type, it proved to be wrong.

Groundwater has also played an important part in earthquake predictions. A peak in radon

in the groundwater at Kobe, Japan 9 days before the 7.2 earthquake cause quite a stir.

Radon levels peaked 9 days before the quake, then fell below the normal levels 5 days

before it hit.

The whole idea behind earthquake predicting is to save lives. With the

improvement in technology, lives have been saved. New ideas and equipment is starting to

prove to be very helpful in predicting were and when an earthquake will strike. The time

and research put into earthquake prediction.

Word Count: 1009

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