A: An earthquake is caused by a sudden slip on a fault. Stresses in the earth's outer layer push the sides of the fault together. Stress builds up and the rocks slips suddenly, releasing energy in waves that travel through the earth's crust and cause the shaking that we feel during an earthquake. An EQ occurs when plates grind and scrape against each other. In California there are two plates the Pacific Plate and the North American Plate. The Pacific Plate consists of most of the Pacific Ocean floor and the California Coast line. The North American Plate comprises most the North American Continent and parts of the Atlantic Ocean floor. These primary boundary between these two plates is the San Andreas Fault. The San Andreas Fault is more than 650 miles long and extends to depths of at least 10 miles. 

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Many other smaller faults like the Hayward (Northern California) and the San Jacinto (Southern California) branch from and join the San Andreas Fault Zone. The Pacific Plate grinds northwestward past the North American Plate at a rate of about two inches per year. Parts of the San Andreas Fault system adapt to this movement by constant "creep" resulting in many tiny shocks and a few moderate earth tremors. In other areas where creep is NOT constant, strain can build up for hundreds of years, producing great EQs when it finally releases.

Q: What is the biggest earthquake ever?

A: Since 1900, the earthquake in Chile on May 22, 1960, is the biggest in the World with magnitude 9.5 Mw.Antarctica has the least earthquakes of any continent, but small earthquakes can occur anywhere in the World.

How to face an earthquake situation?

During an EQ it is not always safe to head for the doorway. If  you live in an old, unreinforced adobe house it is safe. In modern homes doorways are no stronger than any other parts of the house and usually have doors that will swing and can injure you. YOU ARE SAFER PRACTICING THE DUCK, COVER, AND HOLD under a sturdy piece of furniture...Read More tips to face an earthquake

An Israeli aid mission, numbering about 150 personnel, will depart

tomorrow afternoon (29 Jan.) in five Israeli Air Force aircraft to the area of the recent earthquake in Western India. Following an Indian request, Israel is dispatching a entire field hospital, which includes a team of doctors, medical staff, and medical equipment. A foreign ministry team, led by Mr. Moti Amihai the Director of the South East Asia Division, will accompany the delegation Israeli President Moshe Katzav, Prime Minister Ehud Barak, and Foreign Minister Shlomo Ben-Ami have sent messages to the Government of India, expressing Israel's condolences, and its readiness to extend all possible assistance.

The Israeli Foreign Ministry in Jerusalem, and the Israeli Embassy in New Delhi and coordinating the arrival of the Israeli aid effort to the area of Bhuj, in the Indian state of Gujarat, which is the region most effected by the earthquake. The Israeli Ambassador to India, Mr. David Afek, and the Consul-General in Bombay, Mr. Dov Segev-Steinberg will receive the Israeli aid mission in the area of the disaster, and will provide the necessary local coordination for the deployment of the field hospital.

 

 Jabalpur Quake

A severe earthquake of magnitude 6.0 struck Jabalpur and adjoining areas in Madhya Prardesh in the early hours of May 22,1997 which took a toll of 39 (Source: M/O Agriculture) human lives and caused extensive damage to property. The damage was maximum in Jabalpur and Mandla districts but lesser in Chhindwara and Sivni districts. A total of 8267 houses collapsed and more than 40,000 were partially damaged (Source: M/O Agriculture). This earthquake attains significance because it was located very near to an urban conglomeration, the historical city of Jabalpur that bore major brunt of this event.  

Major earthquakes that hit India

Seismic history of Indian Ocean

Articles on Earthquake prediction and technology advances

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Earthquakes can strike any location at any time. But history shows they occur in the same general patterns year after year, principally in three large zones of the earth. The world's greatest earthquake belt, the circum-Pacific seismic belt, is found along the rim of the Pacific Ocean, where about 81 percent of the world's largest earthquakes occur. The belt extends from Chile, northward along the South American coast through Central America, Mexico, the West Coast of the United States, and the southern part of Alaska, through the Aleutian Islands to Japan, the Philippine Islands, New Guinea, the island groups of the Southwest Pacific, and to New Zealand. This earthquake belt was responsible for 70,000 deaths in Peru in May 1970, and 65 deaths and a billion dollars' damage in California in February 1971. 

Why do so many earthquakes originate in this belt? This is a region of young, growing mountains and deep ocean trenches which invariably parallel mountain chains. Earthquakes necessarily accompany elevation changes in mountains, the higher part of the earth's crust, and changes in the ocean trenches, the lower part. The second important belt, the Alpide, extends from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic. This belt accounts for about 17 percent of the world's largest earthquakes, including some of the most destructive, such as the Iran shock that took 11,000 lives in August 1968, and the Turkey tremors in March 1970 and May 1971 that each killed over 1,000. All were near magnitude 7 on the Richter scale. The third prominent belt follows the submerged mid-Atlantic Ridge.
The remaining shocks are scattered in various areas of the world. Earthquakes in these prominent seismic zones are taken for granted, but damaging shocks occur occasionally outside these areas. Examples in the United States are New Madrid, Missouri, and Charleston, South Carolina. Many years, however, usually elapse between such destructive shocks.

Q: Can we cause earthquakes? Is there any way to prevent earthquakes?

A: Earthquakes induced by human activity have been documented in a few locations in the United States, Japan, and Canada. The cause was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies. Most of these earthquakes were minor. The largest and most widely known resulted from fluid injection at the Rocky Mountain Arsenal near Denver, Colorado. In 1967, an earthquake of magnitude 5.5 followed a series of smaller earthquakes. Injection had been discontinued at the site in the previous year once the link between the fluid injection and the earlier series of earthquakes was established. (Nicholson, Craig and Wesson, R.L., 1990, Earthquake Hazard Associated with Deep Well Injection--A Report to the U.S. Environmental Protection Agency: U.S. Geological Survey Bulletin 1951, 74 p.) Other human activities, even nuclear detonations, have not been linked to earthquake activity. Energy from nuclear blasts dissipates quickly along the Earth's surface. Earthquakes are part of a global tectonic process that generally occurs well beyond the influence or control of humans. The focus (point of origin) of earthquakes is typically tens to hundreds of miles underground. The scale and force necessary to produce earthquakes are well beyond our daily lives. We cannot prevent earthquakes; however, we can significantly mitigate their effects by identifying hazards, building safer structures, and providing education on earthquake safety

 

The Himalayas: Two continents collide

Among the most dramatic and visible creations of plate-tectonic forces are the lofty Himalayas, which stretch 2,900 km along the border between India and Tibet. This immense mountain range began to form between 40 and 50 million years ago, when two large landmasses, India and Eurasia, driven by plate movement, collided. Because both these continental landmasses have about the same rock density, one plate could not be subducted under the other. The pressure of the impinging plates could only be relieved by thrusting skyward, contorting the collision zone, and forming the jagged Himalayan peaks.

About 225 million years ago, India was a large island still situated off the Australian coast, and a vast ocean (called Tethys Sea) separated India from the Asian continent. When Pangaea broke apart about 200 million years ago, India began to forge northward. By studying the history -- and ultimately the closing-- of the Tethys, scientists have reconstructed India's northward journey. About 80 million years ago, India was located roughly 6,400 km south of the Asian continent, moving northward at a rate of about 9 m a century. When India rammed into Asia about 40 to 50 million years ago, its northward advance slowed by about half. The collision and associated decrease in the rate of plate movement are interpreted to mark the beginning of the rapid uplift of the Himalayas.

Fifty kilometers north of Lhasa (the capital of Tibet), scientists found layers of pink sandstone containing grains of magnetic minerals (magnetite) that have recorded the pattern of the Earth's flip-flopping magnetic field. These sandstones also contain plant and animal fossils that were deposited when the Tethys Sea periodically flooded the region. The study of these fossils has revealed not only their geologic age but also the type of environment and climate in which they formed. For example, such studies indicate that the fossils lived under a relatively mild, wet environment about 105 million years ago, when Tibet was closer to the equator. Today, Tibet's climate is much more arid, reflecting the region's uplift and northward shift of nearly 2,000 km. Fossils found in the sandstone layers offer dramatic evidence of the climate change in the Tibetan region due to plate movement over the past 100 million years.

At present, the movement of India continues to put enormous pressure on the Asian continent, and Tibet in turn presses on the landmass to the north that is hemming it in. The net effect of plate-tectonics forces acting on this geologically complicated region is to squeeze parts of Asia eastward toward the Pacific Ocean. One serious consequence of these processes is a deadly "domino" effect: tremendous stresses build up within the Earth's crust, which are relieved periodically by earthquakes along the numerous faults that scar the landscape. Some of the world's most destructive earthquakes in history are related to continuing tectonic processes that began some 50 million years ago when the Indian and Eurasian continents first met.

DO NOT turn on the gas again if you turned it off; let the gas company do it DO NOT use matches, lighters, camp stoves or barbecues, electrical equipment, appliances UNTIL you are sure there are no gas leaks. They may create a spark that could ignite leaking gas and cause an explosion and fire DO NOT use your telephone, EXCEPT for a medical or fire emergency. You could tie up the lines needed for emergency response. If the phone doesn't work send someone for help DO NOT expect firefighters, police or paramedics to help you. They may not be available.

Q: What can I expect in my house when an EQ occurs? How do I identify it? What can be done? A: The contents of your home may be damaged and can be dangerous: Shaking can make light fixtures fall, refrigerators and other large items move across the floor, and bookcases and television sets topple over. IDENTIFY: Look around your house for things that could fall or move Ask yourself if your cupboard doors fly open (allowing dishes to shatter on the floor) Is TV and stereo fastened down and are shelves fastened to wall? Do you have hanging plants or light fixtures that might fall? Is there a heavy picture or mirror on the wall over your bed? WHAT CAN BE DONE: You can install door latches, braces and fasteners to fix most of these hazards yourself.

Q: What do I do after an earthquake?

WEAR STURDY SHOES to avoid injury from broken glass and debris. Expect aftershocks CHECK FOR INJURIES (if a person is bleeding, put direct pressure on the wound, use clean gauze or cloth if available; If a person is not breathing administer CPR; DO NOT attempt to move seriously injured persons unless they are in further danger of injury; COVER injured persons with blankets to keep warm; SEEK medical help for serious injuries CHECK FOR HAZARDS (Fire hazards--put out fires in your home or neighborhood immediately, call for help; Gas leaks--shut off main gas valve ONLY if you suspect a leak because of broken pipes or odor; Damaged electrical wiring--Shut off power at the control box if there is any danger to house wiring; Downed or damaged utility lines--do not touch downed power lines or any objects in contact with them; SPILLS--clean up any spilled medicines, drugs, or other harmful materials such as bleach, lye, gas; DOWNED OR DAMAGED CHIMNEYS--Approach with caution--don't use damaged chimney (it could start fire or let poisonous gases into your house; FALLEN ITEMS--beware of items tumbling off shelves when you open doors of closets and cupboards; (4) CHECK FOOD AND WATER SUPPLIES--Do not eat or drink anything from open containers near shattered glass; If power is off, plan meals to use up foods that will spoil quickly or frozen foods (food in the freezer should be good for at least a couple of days; Don't light your kitchen stove if you suspect a gas leak; USE BBQ or camp stoves, outdoors only for emergency cooking; If your water is off you can drink supplies from water heaters, melted ice cubes or canned vegetables (AVOID drinking water from swimming pools or especially spas--it may have too many chemicals in it to be safe

 

"Certainly in the urban areas, people are  traumatized," said Alcedo. "They are afraid to go back into their houses. People are sleeping outside."

FACING AN EARTHQUAKE

Q: What should I do facing an Earthquake?

If you are INDOORS--STAY THERE! (Get under a desk or table and hang on to it, or move into a hallway or get against an inside wall. STAY CLEAR of windows, fireplaces, and heavy furniture or appliances. GET OUT of the kitchen, which is a dangerous place (things can fall on you). DON'T run downstairs or rush outside while the bldg is shaking or while there is danger of falling and hurting yourself or being hit by falling glass or debris.

1. If you are OUTSIDE-- get into the OPEN, away from bldgs, power lines, chimneys, and anything else that might fall on you.
2. If you are DRIVING--stop, but carefully. Move your car as far out of traffic as possible. DO NOT stop on or under a bridge or overpass or under trees, light posts, power lines, or signs. STAY INSIDE your car until the shaking stops. When you RESUME driving watch for breaks in the pavement, fallen rocks, and bumps in the road at bridge approaches.
3. If you are in a MOUNTAINOUS AREA--watch out for falling rock, landslides, trees, and other debris that could be loosened by quakes.

Emergency supplies needed during an earthquake

1. Fire extinguisher
2. Adequate supplies of medications that you or family members are taking
3. Crescent and pipe wrenches to turn off ga
   s and water supplies
4. First-aid kit and handbook
5. Flashlights with extra bulbs and batteries
6. Portable radio with extra batteries
7. Water for each family member for at least 3 days (allow at least 1 gallon per person per day) and purification tablets or chlorine bleach to purify drinking water from other sources
8. Canned and package foods, enough for several days and MECHANICAL can opener. Extra food for pets if necessary
9. Camp stove or barbecue to cook on outdoors (store fuel out of the reach of children)
10. Waterproof, heavy-duty plastic bags for waste disposal.

Plan ahead for an EQ

1. Make sure each member of your family knows what to do no matter where they are when EQs occur:
• Establish a mtg place where you can all reunite afterward
• Find out about EQ plans developed by children's school or day care
• Remember transportation may be disrupted, keep some emergency supplies--food, liquids, and comfortable shoes, for example--at work
2. KNOW where you gas, electric and water main shutoffs are and how to turn them off if there is a leak or electrical short. Make sure older members of the family can shut off utilities
3. LOCATE your nearest fire and police stations and emergency medical facility
4. TALK to your neighbors--how could they help you, or you them after an EQ

5. Things NOT to do during an EQ?