More Frequently Asked Questions (FAQ), Faults
I am trying to locate the nearest active faults to location X, for the purpose of determining the "Near Source Factor" Nv & Na of the '97 UBC. Can you steer me to a web address for this information?
We don't know of a web site for this information. There does exist a joint publication of the UBC and California Division of Mines and Geology which has maps of faults in California and adjacent parts of Nevada at such a scale that this information can be determined. The reference is:
California Department of Conservation Division of Mines and Geology, 1988, Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada: To be used with the 1997 Uniform Building Code, International Conference of Building Officials, Whittier, California, p. 232.
Phone numbers for ICBO (800) 284-4406 or (562) 699-0541
To the best of our knowledge, only the faults appearing in the above publication are required by the UBC to be used in determining near-source factors.
To understand what might be being ignored under this assumption, look at the table found at our web site
http://earthquake.usgs.gov/hazmaps/products_data/48_States/index.php and click on the link "Fault Parameters" under "1996 or 2002 ".
This table includes known active faults with measured slip rates high enough to affect our hazard maps. Consider the state of Wyoming. You will find two Yellowstone faults included in our 1996 hazard maps. Comparing the magnitudes and slip rates for these faults with the definitions found in Table 16-U of the 1997 Uniform Building Code, you will find that these faults would fall in "Seismic Source Type" category C. C category faults have near-source factors of 1.0, which means you don't have to worry about it. (These two faults are assumed to have likelihood's of occurrence less than 1 chance in 1000 per year.)
Such a comparison could be made for faults in other states not included in the CDMG publication.
