FAQs - National Seismic Hazard Maps
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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?
- 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?
- 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.
- After downloading the application, how do I install it?
- When I run the application I get an error message saying "Could not find the main class. Program will exit." What is wrong?
- When I run the application I get an error message saying "Could not establish a connection to the server. Our server may be temporarily down..." What should I do?
- I downloaded the file and unzipped it, but I can't find an executable. How do I run the application?
- How do I know which version of Java I am using?
- I input incorrect proxy information and now the application does not prompt me to correct it. How can I change this?
- Our proxy server requires authentication (username and/or password), how can we set this information?
- I am still having problems, who can I contact for assistance?
