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Frequently Asked Questions
Earthquake Myths
- Can you predict earthquakes?
- Can animals predict earthquakes?
- Can some people sense that an earthquake is about to happen? (earthquake sensitives)?
- Is there earthquake weather?
- Are there more earthquakes in the morning/in the evening/at a certain time of the month?
- Can the ground open up during an earthquake?
- Will California eventually fall off into the ocean?
- Do earthquakes cause volcanoes?
- Can you prevent large earthquakes by making lots of small ones, or by "lubricating" the fault with water or another material?
- Why are we having so many earthquakes? Has earthquake activity been increasing? Does this mean a big one is going to hit? OR We haven't had any earthquakes in a long time; does this mean that the pressure is building up?
- What is the "Triangle of Life" and is it legitimate?
- Where can I buy a Richter scale?
- Do solar flares or magnetic storms (space weather) cause earthquakes?
Earthquakes, Faults, Plate Tectonics, Earth Structure
- Can we cause earthquakes? Is there any way to prevent earthquakes?
- What do we know about the interior of the Earth?
- Can earthquakes be predicted?
- What is plate tectonics?
- What is a fault and what are the different types?
- What is the relationship between faults and earthquakes? What happens to a fault when an earthquake occurs?
- How do we know a fault exists?
- Where can I go to see the/a fault?
- Where can I get seismic hazard maps?
- Where can I find information about faults in my area?
- How can I find out about earthquakes in my area?
- Where can I find information about volcanoes?
- How can I find out about tsunamis?
- What is an earthquake and what causes them to happen?
- At what depth do earthquakes occur?
- What is surface faulting or surface rupture in an earthquake?
- Foreshocks, aftershocks - what's the difference?
- Can the position of the moon or the planets affect seismicity?
- Two earthquakes occurred on the same day. Are they related?
- Where can I get a fault map?
- Do earthquakes occur in Antarctica?
- What is the significance of the depth of an earthquake?
Measuring Earthquakes
- Where can I buy a Richter scale?
- Why are there often different magnitudes reported for the same earthquake?
- What is moment magnitude?
- When was the first instrument that actually recorded an earthquake?
- What is a P wave? An S wave?
- What does an earthquake look like?
- What is intensity? What is the Modified Mercalli Intensity Scale?
- What is the difference between intensity scales and magnitude scales?
- What is acceleration, velocity, and displacement?
- What is spectral acceleration?
- What are those beachball figures?
- How much energy is released in an earthquake?
- What are UTC and GMT (in reference to the time of an EQ)?
- What does it mean that the earthquake occurred at a depth of 0 km?
- How are earthquakes recorded? How are earthquakes measured? How is the magnitude of an earthquake determined?
- What are the different magnitude scales, and why are there so many?
- How do you give a Richter magnitude to earthquakes that occurred prior to the scale?
- What was the duration of the earthquake? Why don't you report the duration of each earthquake? How does the duration affect the magnitude?
- How do seismologists locate an earthquake?
Latest Earthquake Maps & Information
- Can I get on a list to receive an email message when there is an earthquake? How do I sign up for earthquake notifications?
- How can I report an earthquake experience or related observation?
- Where can I see current or past seismograms?
- Why do so many earthquakes occur at a depth of 10km?
- How do the earthquakes get to the webpages?
- Why do some earthquakes disappear?
- Why isn't the distance to the nearest fault provided?
- What is the reference point for the places?
- How fast does the earthquake information get posted to the web site, get sent out via the Earthquake Notification Service (ENS), ATOM feeds, etc?
- When does the USGS update the magnitude of an earthquake?
- When are tsunami information and links put on the event page?
- Why is the earthquake that was reported/recorded by network X, or that I felt, not on the map/list?
- What is the map projection for the earthquake map, and what is the reference model used?
- How are the reference places chosen?
Earthquake Effects & Experiences
- Where can I find photographs of earthquake damage?
- Why do earthquakes in other countries seem to cause more damage and casualties than earthquakes in the U.S.?
- How do you classify/measure the shaking that you feel during an earthquake? Sharp jolts versus rolling motion?
- What are isoseismal maps?
- What is liquefaction?
- What are the effects of earthquakes?
- Where have tsunamis occurred historically?
- At what magnitude does damage begin to occur in an earthquake?
- What does an earthquake feel like?
- What are those booms I sometimes hear before or during an earthquake?
- How can an earthquake effect groundwater or changes in wells?
Seismographs
- What is a seismometer? What are seismographs? How do they work?
- What are seismograms? How do you read them?
- How is the movement of the seismometer converted into a seismogram?
- How can I make my own seismometer?
Historic Earthquakes and Statistics
- What is the biggest earthquake ever?
- What is the biggest earthquake in the United States?
- Which States in the United States have the most earthquakes?
- Which State has the most damaging earthquakes?
- Which States have the smallest number of earthquakes?
- How many earthquakes worldwide occur each day? Each year?
- Where can I find a list of the largest earthquakes near my town?
- Where can I find a list of the most destructive earthquakes in the world?
- Where can I find a list of the largest earthquakes in the United States?
- Where can I find other lists of earthquakes?
- Can I do an earthquake catalog search to get my own list of earthquakes?
- Where do earthquakes occur?
- I want to move to a place that doesn't have earthquakes. Where can I go?
- Which Country has the most earthquakes?
Probabilities, Seismic Hazard & Earthquake Engineering
- Are earthquake probabilities or forecasts the same as prediction?
- What is the probability that an earthquake will occur in the Bay Area?
- What is the probability that an earthquake will occur in the LA Area?
- What is seismic hazard and how is it determined?
- Where can I find seismic hazard maps?
- How do earthquakes affect buildings?
- How will my house hold up in an earthquake? Can the USGS send someone out to evaluate my property?
- How are engineers working to make roads and buildings safer?
- What are the Guidelines for evaluating and mitigating seismic hazards in California?
- What is the USGS doing to mitigate and respond to earthquake hazards?
- How do I decide whether or not to get earthquake insurance?
- What is the probability that an earthquake is a foreshock to a larger earthquake?
- Is it safe to go to X since they've been having a lot of earthquakes lately?
- What are the earthquake risks where I live?
Earthquakes Induced by Fluid Injection
- What work is the USGS doing to better understand the occurrence of injection- induced earthquakes?
- Is the recent sequence of earthquakes near Youngstown, Ohio, related to the wastewater disposal activities there?
- Are earthquakes induced by fluid-injection activities always located close to the point of injection?
- Is there any possibility that a wastewater injection activity could interact with a nearby fault to trigger a major earthquake that causes extensive damage over a broad region?
- Is it possible to anticipate whether a planned wastewater disposal activity will trigger earthquakes that are large enough to be of concern?
- Do all wastewater disposal wells induce earthquakes?
- How large are the earthquakes induced by fluid injection?
- How does the injection of wastewater at depth cause earthquakes?
- Does the production of natural gas from shales cause earthquakes? If so, how are the earthquakes related to these operations?
- Do you have a video that discusses this topic?
Earthquake Preparedness
- During an EQ should you head for the doorway?
- What emergency supplies do I need?
- How can I plan ahead for an EQ?
- What should I do during an EQ?
- Things NOT to do during an EQ?
- What can I expect in my house when an EQ occurs? How do I identify it? What can be done?
- What do I do after an earthquake?
- What are the steps to EQ safety/awareness?
California
- Why are there so many earthquakes in the Geysers area in Northern California?
- Will California eventually fall off into the ocean?
- Why are there no faults in the Great Valley?
Other Resources
- What are some good books on earthquakes and geology?
- Where can I find educational materials?
- Where can I find other online resources on earthquakes?
Did You Feel It?
- Why don't you have the earthquake I felt?
- I accidentally filed an unknown report before the earthquake I felt was in the system. Can I go back and change my report?
- Why isn't my zip code on the map?
- Why don't you use Canadian zip codes?
- How do you calculate Global DYFI?
- The earthquake was in my area, but I didn't feel it. Should I still fill out this form?
- What is intensity?
- What is geocoding?
- What time is GMT?
- Do you have a printable version of the report form for those without access to the Internet?
- How is my personal information used? Can others access my personal information?
- How do you filter erroneous responses?
- This earthquake was a rolling one, but the one the other day was a jolt. Why the difference?
- How long was the shaking?
- Can people predict earthquakes? Will there be more after this one? Is there a pattern?
- Where can I find information about seismicity in my area?
- What can I do to prepare for an earthquake? How can I keep my family safe?
- How is my "Did you feel it?" input used?
- My question is still unanswered. Where do I go now?
PAGER
- What is PAGER?
- How does PAGER work?
- Who will use this new product?
- What is the Earthquake Impact Scale?
- How frequently will yellow, orange, and red PAGER alerts occur?
- By linking economic losses with human losses to create an alert, is the USGS putting a value on human life?
- Is this a new program/system or just an update?
- How can you be so sure that your loss or impact estimates will be accurate?
- Then why not wait until you're 100% positive about the exact numbers?
- What if you're wrong? How will we be able to trust the information that you provide?
- PAGER addresses losses directly due to earthquake shaking. What about tsunami and other potential hazards related to the earthquake (fire, landslides, liquefaction)?
- Is there a concise, printable version of PAGER results?
- Which earthquakes are analyzed by the PAGER system?
- How long after an earthquake are PAGER results available?
- What is the Modified Mercalli Intensity scale and how is it different from magnitude?
- How are the estimated ground motion intensities calculated?
- What happens when reported damage and casualty reports become available? Do you update the PAGER loss model?
- Are PAGER results available by e-mail?
National Seismic Hazard Maps
- General Questions
- Why are there different probability maps, and which one do I use?
- I am having problems logging into your FTP site. Is this my problem or yours?
- I am publishing a book (journal article, thesis, pamphlet, poster, postcard, T-shirt, etc.), and I wish to use one of the NEHRP national hazard maps as an illustration. Who do I contact to obtain permission to do this?
- What is probabilistic ground motion?
- I need a simple description of what the maps are about.
- How do I use these maps?
- I am trying to calculate the ground motion effect for a certain location in California. I obtained the design spectrum acceleration from your site, but I would like to identify the soil type of this location, how can I reach it?
- What is the likelihood of a large earthquake at location X?
- Why aren't these maps 0, 1, 2, 3, 4 Zone maps?
- Why are the maps not simple 0, 1, 2, 3, 4?
- Where do I find a 0, 1, 2, 3, 4 map?
- How do I get zone maps for locations outside of the US?
- What is a seismic zone?
- What zone is location X in?
- What is the zone number for Federal Site Z?
- What does the "Geolocate Me" option in the address input bar on the map mean?
- What do the ground-motion parameters on these maps mean?
- What is "Peak Acceleration" or "Peak Ground Acceleration" (PGA)?
- What is "% g"?
- If I were to use an accelerometer to measure seismic events, how could I convert the acceleration data (in g's) to the magnitude numbers you folks use?
- What is "probability of exceedance" or PE?
- What is "spectral acceleration" or SA?
- What is percent damping?
- Your map is for ground motions having a 2% probability of exceedance in 50 years. Are those values the same as those for 10% in 250?
- Your map values show ground motions that have a probability of being exceeded in 50 years of 10, 5 and 2 percent. What is the probability of their being exceeded in one year (the annual probability of exceedance)?
- What is the relationship between peak ground acceleration PGA and "effective peak acceleration," Aa, or between peak ground velocity and "effective peak velocity," Av, as these parameters appear on building code maps?
- A certain ground motion has an x percent probability of being exceeded in Y years. What is the probability, w that that same ground motion is exceeded in Z years? See the next FAQ.
- 2009 Earthquake Probability Mapping Application
- Is this an earthquake forecast tool for the near future?
- What is the basis of the forecast?
- What is meant by an “earthquake” in this forecast?
- Ok, so why do you decluster the catalog?
- What if we need to know about total rates of earthquakes with M>5 including aftershocks?
- What is the difference between the probability map and the report at this web site?
- What maximum distance should I use when preparing the report?
- What is a distance metric?
- How can I use this information?
- I'm having difficulty using this application, who can I contact for assistance?
- Why is the choice of distance metric important in probability assessments?
- I have a miscellaneous map question.
Global Vs30 Map Server
- I got an error message during my calculation. What's wrong?
- Why can't I draw a region on the map? Why is the rectangle not behaving correctly?
- The map isn't working properly. Help!
- I closed the popup window with my calculated results. How do I get them back?
