Frequently Asked Questions
Under construction!
We are putting together a list of frequently asked questions. Please drop us a line if you don't see your questions here! You can send us email at www@ncedc.org or fill out our comments form.
- How can I get a list of earthquakes near my house (business, or other point of interest)?
- I can't find an earthquake that I know occurred at a particular time. Why not?
- Can I make a map of the earthquakes from the search?
- Can I search across the -180/180 meridian?
- How do I access the teleseisms recorded by the NCSN?
- How can I get a list of earthquakes near my house (business, or other point of interest)?
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The first step is to determine the latitude and longitude of your point of interest. One resource for this is Zipinfo.com, which does a free ZIP code lookup (the success of this option depends on how large your ZIP code is!), or the USGS Query form for geographical features. Once you have the coordinates, decide whether the northern California or the global catalog is more appropriate for your search. Once you have selected the catalog, use the delta feature of "additional search parameters" in the form to specify your point of interest.
For example, the coordinates of UC Berkeley in Berkeley, CA, are 37.8735, -122.2609. To obtain a list of earthquakes within 2 km of these coordinates, enter
delta=37.8735,-122.2609,0,2
This will return all events within a 2 km radius circle of the specified coordinates. When this search is run on the NCSN catalog for the year 2001 for all magnitudes, it returns 1 earthquake:
2001/01/30 10:35:34.36 37.8785 -122.2473 9.29 1.05 coda
If your search does not return any earthquakes, consider enlarging the radius of your circle (remember, the circle radius is specified in kilometers, not miles!). If you need help with the conversion, try out our converter. Or double check the sign of longitude. The catalog search requires that West longitudes are specified with negative numbers.
For more details, please see the help pages for either the Northern California or the Global earthquake catalog searchs.
- I can't find an earthquake that I know occurred at a particular time. Why not?
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In order to prevent confusion with the myriad of time zones around the world, seismologists use a single standard of time for reporting on earthquakes. Universal Time (UTC) is the agreed standard for earthquake reporting and is also known at Greenwich Mean Time (GMT) or Zulu time (Z). Universal Time is based on a 24-hour clock. Although useful - and necessary - to coordinate seismological observations around the world, the use of UTC can be confusing. For northern California, the classic example is the 1989 Loma Prieta earthquake, which occurred on Oct 17 17:04 local time and Oct 18 00:00 UTC. Need some help with conversion? Check out our conversion utility.
- Can I make a map of the earthquakes from the search?
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Unfortunately, we do not currently support a tool for generating maps of the earthquakes produced from the catalog searchs.
- Can I search across the -180/180 meridian?
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The default "box" search over latitude and longitude does not support searchs across the -180/180 meridian. Neither does the polygon search option. This is due to the complications of determining whether an earthquake is inside or outside the polygon for searchs spanning the meridian. To do this type of search, you must break your request into two separate searchs.
- How do I access the teleseisms recorded by the NCSN?
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First, check the list of teleseisms recorded by the NCSN and then check their loading status. Using the event id from the list, you can retrieve the data using EVT_FAST form.
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Northern California Earthquake Data Center
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Copyright 1995-2005, The Regents of the University of California.
Last modified: Thu Oct 15 10:15:41 PDT 2009