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Fault Maps

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Just got off the phone with a soils engineer who is claiming that the fault
maps from the 1997 UBC / California Division of Mines & Geology is off
almost 3.5km for a type A fault. He uses the Alquist-Priolo Special Studies
Zone Maps instead of the ICBO Published maps most of us probably use.

The Faults in question are the Hayward (Type A) and the Hayward Southeast
Extension (Type B) in Fremont, CA. Based on the UBC maps, the Site is 4.5km
from the Type A fault and 2.0km from the Type B Fault.. At these distances,
the type B fault governs for Seismic Design (Using interpolation of the
distances and type Sd soil). See map F-19 from the UBC Mines and Geology map
book Where highways880 and 238 intersect.

The "soils" engineer (a C.E. not a G.E.), is telling me that based on the
Alquist-Priolo Maps, The site is 4,000 feet from the Type A Fault.

The city building official agrees with the Type B fault, less than 2.0km we

This seems ridiculous to me that there can be such a discrepancy. Has anyone
else experienced anything similar to this? Perhaps someone with a Geotech
background could explain this huge difference in the location of a known

Gerard Madden, P.E.
Civil Engineer/Structural Designer

The Bentley Company,
A Division of Enron Energy Services North America, Inc.
Email: gmadden(--nospam--at)
Ph: 510.661.0527 (Fremont)
Fx: 510.661.0528 (Fremont)