Earth Quakes

What cause earth quakes?

An earthquake is a sudden shaking or disturbance of the earth’s surface caused by movements in the earth’s outer layer. Energy, which naturally occurs within the earth, becomes disturbed or strained (creating a fault), and releases itself, causing the violent shaking that we define as an earthquake.

A fault is a layer in the earth’s outer surface where rocks have moved due to high levels of energy. Once a fault slips, vibrations occur, and an earthquake results.

Aftershocks are as small earthquakes which come immediately after an earthquake. Aftershocks are felt as a series of shaking movements and most often accompany larger earthquakes.


The term “seismology” is greek and literally defined as “to shake.” The study of earthquakes is defined as seismology.

SEISMOLOGISTS are scientists who research and study earthquakes and their patterns. By carefully analyzing the earth’s surface before, during, and after a quake, seismologists are able to see how the earth’s energy moves. In recent years, extensive study by seismologists has been able to pinpoint the devastating effects of quakes and educate the public on how to prepare for the violent ground shaking. Such work has assisted in reducing property and structural damage, injury, and death around the world.

SEISMOGRAPH is a scientific machine used to record movements within the earth’s surface.

RICHTER SCALE is not a machine, but a mathematical formula which determine the the strength of waves recorded on a seismograph. The resulting measurement defines the exact size of the quake.

Although it’s possible for earthquakes to occur in any area of the world, seismologists have concluded that most quakes are seen and felt in three specific areas:


This area is found around the outer edges of the Pacific ocean. Nearly 80-percent of all large quakes occur in this region. The Pacific seismic belt measures from Chili to South America to the western region of the United States, including the southern tip of Alaska, the Aleutian Islands, Japan, New Guinea and New Zealand.


The Himalayas, Mediterranean and the Atlantic make up the Alpide belt region. Approximately 18-percent of all earthquakes occur in this area.


The mid-atlantic ridge is the third most likely area where quakes occur, and covers the region of from the north-south axis of the Atlantic to the Arctic Ocean to the southern-most tip of Africa.

In the United States, Alaska and California see more earthquakes each year than any other State. Florida and North Dakota are rarely affected by quakes.


Earthquakes take place everyday. In fact, several hundred earthquakes are noted each day around the globe. Fortunately, most are too small to be felt. Each day, seismographs detect and record minor movements within the earth, most of which are not felt and do not cause damage. Small quakes are technically known as “very minor,” “minor” and “light” quakes, measuring between 3-4 on the Richter scale.


Moderate earthquakes happen approximately 15-20 times per year. Moderate quakes measure 5-6 on the Richter scale and can cause millions of dollars in property damage.


Larger quakes pass every few years and are classified as “strong,” “major” or “great.” Large earthquakes measure a 6 or above on the Richter scale. The largest-ever quake occurred in Chile on May 22, 1960. It measured 9.5 on the Richter scale.


The physical effects of an earthquake are felt for 2-3 minutes. Within that short amount of time, a tremendous amount of destruction can take place. Depending on the type and strength of the quake, damage can be seen in soil, buildings, homes, pipelines, railways, bridges, and people. Earthquakes very often cause fires, disease, contaminated water sources, Tsunami Waves, and infection.


Although earthquakes are not preventable, disaster control measures can be taken to help reduce the effects of structural damage, injury and death.

1. Know where emergency supplies are located. Time is of the essence during and after a quake, and acting quickly can save lives. Know where emergency supplies are kept, including fire extinguishers, medications, First Aid Kits, tools, fresh drinking water, flashlights, and portable radios and phones.

2. Educate every family member as to what to do during a quake, and find a central location of the house to meet following a quake, to ensure the safety of all.

3. Know where your water, electric and gas shut-off valves are located and how to operate them.


IF YOU ARE OUTSIDE when a quake occurs, run to the nearest open area, as far away from buildings, trees, mountains, power lines, glass windows and structures, and bridges as you can.

INSIDE, move to an area where you can ground yourself and receive cover. Crawl under a heavy desk or table and hang on. Stay away from windows, doors, fireplaces, chimneys, washers and dryers, kitchens, and electrical areas.

IF YOU’RE IN YOUR CAR when a quake begins, stop driving and move your car to the side of the road. Never stop under an overpass or bridge, and steer clear of trees, power lines, light poles, and signs. Remain in your car until the quake has finished.

Most seismologists also recommend checking structures to ensure they are made of earthquake resistant materials. Earthquake insurance is also available to those who live in high risk areas.