Fast Facts about
Earthquakes
- Earthquakes strike suddenly, violently, and without warning at any time of the year and at any time of the day or night.
- Smaller earthquakes often follow the main shock.
- An earthquake is caused by the breaking and shifting of rock beneath the Earth's surface. Ground shaking from earthquakes can collapse buildings and bridges; disrupt gas, electric, and phone service; and sometimes trigger landslides, avalanches, flash floods, fires, and huge, destructive ocean waves (tsunamis).
- Most earthquake-related injuries result from collapsing walls, flying glass, and falling objects.
- Several thousand shocks of varying sizes occur annually in the United States, and 70 to 75 damaging earthquakes occur throughout the world each year. All 50 states and all U.S. territories are vulnerable to earthquakes. Where earthquakes have occurred in the past, they will happen again.
- California experiences the most frequent damaging earthquakes; however, Alaska experiences the greatest number of large earthquakes—most located in uninhabited areas.
- Earthquakes occur most frequently west of the Rocky Mountains, although historically the most violent earthquakes have occurred in the central United States.
- The largest earthquakes felt in the United States were along the New Madrid Fault in Missouri, where a 3-month-long series of quakes from 1811 to 1812 included three quakes larger than a magnitude of 8 on the Richter Scale. These earthquakes were felt over the entire eastern United States (over 2 million square miles), with Missouri, Tennessee, Kentucky, Indiana, Illinois, Ohio, Alabama, Arkansas, and Mississippi experiencing the strongest ground shaking.
- The Richter Scale, developed by Charles F. Richter in 1935, is a logarithmic measurement of the amount of energy released by an earthquake. Earthquakes with a magnitude of at least 4.5 are strong enough to be recorded by sensitive seismographs all over the world.
- It is estimated that a major earthquake in a highly populated area of the United States could cause as much as $200 billion in losses.
FEMA: What to Do Before an Earthquake
Earthquakes strike suddenly, violently and without warning. Identifying
potential hazards ahead of time and advance planning can reduce the dangers
of serious injury or loss of life from an earthquake. Repairing deep plaster
cracks in ceilings and foundations, anchoring overhead lighting fixtures
to the ceiling, and following local seismic building standards, will help
reduce the impact of earthquakes.
Six Ways to Plan Ahead
- Check for Hazards in the Home
- Fasten shelves securely to walls.
- Place large or heavy objects on lower shelves.
- Store breakable items such as bottled foods, glass, and china in low, closed cabinets with latches.
- Hang heavy items such as pictures and mirrors away from beds, couches, and anywhere people sit.
- Brace overhead light fixtures.
- Repair defective electrical wiring and leaky gas connections. These are potential fire risks.
- Secure a water heater by strapping it to the wall studs and bolting it to the floor.
- Repair any deep cracks in ceilings or foundations. Get expert advice if there are signs of structural defects.
- Store weed killers, pesticides, and flammable products securely in closed cabinets with latches and on bottom shelves.
- Identify Safe Places Indoors and Outdoors
- Under sturdy furniture such as a heavy desk or table.
- Against an inside wall.
- Away from where glass could shatter around windows, mirrors, pictures, or where heavy bookcases or other heavy furniture could fall over.
- In the open, away from buildings, trees, telephone and electrical lines, overpasses, or elevated expressways.
- Educate Yourself and Family Members
- Contact your local emergency management office or American Red Cross chapter for more information on earthquakes. Also read the "How-To Series" for information on how to protect your property from earthquakes.
- Teach children how and when to call 9-1-1, police, or fire department and which radio station to tune to for emergency information.
- Teach all family members how and when to turn off gas, electricity, and water.
- Have Disaster Supplies on Hand
- Flashlight and extra batteries.
- Portable battery-operated radio and extra batteries.
- First aid kit and manual.
- Emergency food and water.
- Nonelectric can opener.
- Essential medicines.
- Cash and credit cards.
- Sturdy shoes.
- Develop an Emergency Communication Plan
- In case family members are separated from one another during an earthquake (a real possibility during the day when adults are at work and children are at school), develop a plan for reuniting after the disaster.
- Ask an out-of-state relative or friend to serve as the "family contact." After a disaster, it's often easier to call long distance. Make sure everyone in the family knows the name, address, and phone number of the contact person.
- Help Your Community Get Ready
- Publish a special section in your local newspaper with emergency information on earthquakes. Localize the information by printing the phone numbers of local emergency services offices, the American Red Cross, and hospitals.
- Conduct a week-long series on locating hazards in the home.
- Work with local emergency services and American Red Cross officials to prepare special reports for people with mobility impairments on what to do during an earthquake.
- Provide tips on conducting earthquake drills in the home.
- Interview representatives of the gas, electric, and water companies about shutting off utilities.
- Work together in your community to apply your knowledge to building codes, retrofitting programs, hazard hunts, and neighborhood and family emergency plans.
Can We Predict Earthquakes?
Host: Jessica Robertson
The recent, devastating earthquake in China, Haiti and Chile has sparked discussion about whether earthquakes can be predicted. USGS scientist Mike Blanpied sets the record straight on what science is capable of.
Jessica Robertson
Hello and welcome to the USGS CoreCast. I'm Jessica Robertson. Today I would like to welcome and introduce you to our guest, USGS Scientist, Michael Blampied. He is going to talk to us about earthquake prediction. Thank you for joining us today, Mike.
Mike Blanpied
Nice to be here.
Jessica
First I would like to know, can the USGS or any other agency predict earthquakes?
Mike
Jessica, there's currently no organization or government or scientist capable of successfully predicting the time and occurrence of earthquake. However scientists are very good at saying things more general about earthquake hazards and earthquake risks. For example we can look at faults and patterns of earthquakes over many years and we can do a pretty good job of saying where on the landscape we're likely to have earthquakes on which faults, how big those earthquakes are likely to be and about how heavy the shaking is likely to be from those earthquakes.
Using that information, um, we can improve building codes, we can do ah, land use planning, we can avoid buildings next to faults that are hazardous and so forth. So we can forecast in the long term where the earthquake hazard is likely to be."
Jessica
I know that after large earthquakes, it is likely that aftershocks may occur. Can you predict the size and timing of these aftershocks?
Mike
Following any large earthquake, there will be a number of aftershocks. After a very large earthquake there may be many aftershocks and they may go on for months or even years. However, they decrease in frequency and generally decrease in size over time. Scientists can say about how often and how many aftershocks will occur but not exactly when or where.
The other thing scientists do following a large earthquake is to calculate the amount of stress that was moved onto nearby faults in the area increasing their risk of large earthquakes.
Jessica
Has the USGS done experiments to predict earthquakes?
Mike
Yes. USGS has done and has sponsored much research over several decades on earthquake prediction, both specific prediction experiments and also more general research to understand the predictability of earthquakes. For example is there something that happened in the earth ahead of an earthquake that would allow it to be detected at the surface?
The USGS and the state of California engaged in a really careful experiment on earthquake prediction. In Central California, there's a stretch of the San Andreas fault that runs through a small town called Parkfield in Central California and back in the 80s it was noticed that there had been a pattern of earthquakes of about a magnitude 6, several of these earthquakes over time spaced out about every 20 to 25 years, the last one occurring in 1966. On the basis of that pattern, the USGS and the state predicted that there would be another one coming probably in the mid 80s. And that led to a very intensive experiment to try to capture all the information possible about that earthquake with a variety of instruments and also to predict it if possible. It turned out that the earthquake did not come in the 80s and it did not come in the 90s. It actually waited until 2004.
We did capture wonderful information about the earthquake using a variety of sensors, however, there was nothing that we could tell that was predictable about the earthquake. The earth gave no indication with a foreshock or an electric signal or a water signal or anything else that an earthquake was about to begun. It just demonstrates to us what we've already learned over several years and several decades that earthquake prediction, if it's possible at all is really hard.
Jessica
So can you give us an example of what we can forecast about a particular fault?
Mike
Well the Hayward fault in the eastside of the San Francisco Bay is a great example. The Hayward fault has a very long history of earthquakes and geologists have dug into the fault zone and looked at the rocks to determine that earthquakes in the Hayward fault happen about every 140 years with some variation. It's been 140 years since the 1868 earthquake that did a great deal of damage in the San Francisco Bay and therefore the Hayward fault is one could say about due for an earthquake.
Now there is a lot of variability in how periodic those earthquakes are so we can't say whether the next earthquake will happen tomorrow or 10 years or even 20 years from now. But we do know that that earthquake is very likely, we think it's likely to be about a magnitude of 6.8 earthquake and therefore very dangerous. And we can take steps now to safeguard the Bay area against that earthquake that we're pretty darn sure is coming."
Jessica
Now I've heard that animal behavior can predict earthquakes. Is that true?
Mike
There has been a fair amount of research on this topic in various places and as far as I understand there's been no demonstration that earthquakes are specially predictable by animals, however, research does continue on this topic. One thing that is clear is that some animals are very sensitive to various live vibrations on the ground.
And so oftentimes an animal will detect the early arrival of the faint waves that come out first from an earthquake and become aware that the ground is shaking before the humans around them become aware of the more heavier shaking that follows. And so an earthquake may cause animals to react a few seconds or even a minute before the humans nearby.
Jessica
So can the USGS or any other agency do the same thing and detect these early waves?
Mike
Yes in fact there's quite a bit of work in that area and your listeners may be aware of P wave detectors or simple devices that one can for example hook up to your gas line in your house. That device basically feels for gentle shaking and if it detects that gentle shaking, it will shut off the gas before the arrival of the heavier shaking to follow. The other way that we can do this early warning is to place seismometers in the vicinity of where there's going to be an epicenter of an earthquake in high hazard areas. When the earthquake occurs the seismic network very quickly measures the earthquake and computers can determine that an earthquake has begun and that information can be radioed ahead to areas that have not yet received a strong shaking.
We call this system earthquake early warning, and there are operational systems in Mexico and in Japan and the USGS and partner organizations in California are doing research to understand what benefits an earthquake early warning system might have in California."
Jessica
What exactly is the USGS's role in earthquake science and prediction?
Mike
The USGS actually has a unique role in earthquake prediction research. USGS is a federal agency that has the responsibility for issuing warnings for geologic disasters such as earthquakes, landslides and volcanoes. This includes the federal responsibility for issuing earthquake predictions.
Jessica
Is there anything else you want to share with us today?
Mike
I simply want to make the point that well we don't have a method for predicting earthquakes as discussed. There is grounds for optimism. There is increased amounts of data, new theories and powerful computer programs and scientists are using those to explore ways that earthquakes might be predicted in the future. We can certainly hope that someday we'll be in a world where an earthquake can be anticipated and predicted before it occurs.
Jessica
Well thank you for joining us today Mike.
Mike
It was nice talking with you.
Jessica
And thank you to all our listeners who joined us for this episode of CoreCast. If you would like real time and historic information about earthquakes worldwide or to learn more about earthquake science, visit earthquake.usgs.gov. If you feel an earthquake, please report your experience on the didyoufeelit site located on the USGS earthquake Web site.
As always CoreCast is a product of the US Geological Survey Department of the Interior.
Music credit:
"throu" by calpomatt
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Excellent and very descriptive blog. thanks
ReplyDeleteGeorge