Enhanced Geothermal Systems
Earthquake Catalog Search Help
The earthquake catalogs may be filtered using several different parameters including time, location (latitude and longitude), magnitude, and depth. Additional criteria are available.
All time in the earthquake catalog is referenced to UTC. Date and time parameters can be specified in one of several formats:
- yyyy = year (1900-present)
- doy = day-of-year (1-366) >li>mm = month (1-12)
- dd = day-of-month(1-31)
- HH = hour (0-23)
- MM = minute (0-59)
- SS = second (0-59.9999)
- Latitude and Longitude parameters
Latitude and Longitude values can be specified in one of two formats:
- decimal degrees, such as 39.50 for 39 and one-half degrees.
- degrees and minutes, such as 39:30 for 39 degrees and 30 minutes.
- Longitude for California is WEST, and therefore should be specified as NEGATIVE (eg -121.5 for 121.5 degrees West).
- Since longitude is signed, a search between longitudes of -117 and -121 should be specified with a Min longitude = -121 and a Max longitude = -117.
The USGS GNIS Mapping Query Form can be used to find the latitude and longitude of a specific town or geographic feature.
- Additional search parameters
Additional search parameters for selecting earthquakes may be specified by entering the appropriate keyword=value strings in the "Additional Search Parameters" box. Most search parameters are min/max parameters which allow you to provide minimum and/or maximum values for specific fields in the event catalogs. However, you may also select earthquakes within a specified annulus (or ring) around a location with the delta parameter, or specify a polygonal region to confine your earthquake search to a more complex region than a simple latitude/longitude box.
Search parameters that have min and max values can be specified by the strings
- minclose=1 maxclose=20
The following keywords can be used in min and max values parameter strings:
- sta - number of stations used for solution (range: 0 to ...).
- close - distance of closest station to epicenter (range: 0 to ...).
- rms - root-mean-squared residual of solution (range: 0. to 1.).
- gap - azimuthal gap (range: 0 to 360).
You may search for all earthquakes that are within an annulus (ie between a minimum and maximum distance) from a location with the delta parameter.
specifies a circle (annulus with inner diameter of 0) of 50 km around the location (38,5,-118.5). The program will select only earthquakes that are located within this circle.
specifies an annulus (ring) of 20 to 50 km around
the location (38,5,-118.5). The program will select only earthquakes
that are located within this annulus.
WARNING: The delta function will break if the circle centered at lat,lon with diameter of maxdist kilometers contains either of the earth's poles.
You may specify a polygonal search area with the polygon parameter.
defines a polygon that encloses that Bay Area Peninsula.
By default, the output from the search will be returned to your browser in another document. Most browsers have the capability of directing a document directly to a local disk file instead of displaying it on the screen.
If you think that the search may generate more data than your brower can safely display, you should either set your browser to download documents directly to disk, so that the results of the search will be placed on your computer's disk, or you should specify that the output should be sent to an anonymous ftp file at the NCEDC.
If you send the output to anonymous ftp, you will be informed of the pathname and URL for the file so that you can retrieve it at your convenience. Please delete the file from the NCEDC when you are finished with it. The file will be automatically deleted in within several days if you do not delete it.
- Line Limit
It is very easy to generate a lot of unwanted output by inadventently
mis-typing any of the search parameters. For example, entering a minimum
magnitude of 0.5 instead of 5.0 can signicantly alter the number of matches
from a catalog search, and can easily generate megabytes of output from a
phase retrieval request.
In order to protect yourself (and the NCEDC) from runaway searches, you should limit the number of lines that the search will generate before it is aborted. If you set this limit to a reasonable value on your desired request, it can help to prevent runaway searches that can result from mis-typed values.
You can disable the output line limit by deleting the value in the line limit field, or by entering a value of 0. Please use this setting with extreme caution.