Homework 1 (pdf) - Geotechnical Earthquake Engineering

for the city of Charleston (in the Charleston seismic region). These are the two principal
“eastern U.S.” seismic zones. Plot both spectra on the same plot.
(d) Now consider Charleston a bit more closely. Plot approximate Equal Hazard Spectra for
Charleston for both the 10% probability of exceedance in 50 years (~475 year return
interval) level, and the 2% probability of exceedance in 50 years (~2,500 year return
interval) level [Plot these both on the same figure.] Using the 1996 “deaggregation”
option, deaggregate these spectra by Magnitude (M) and Distance (R). Note that the
deaggregation will be different at shorter and longer periods, so you will want to
deaggregate for PGA and for the various spectral ordinates separately.
• Using your Equal Hazard Spectrum for 10% in 50 years, and the
deaggregation, recommend the approximate initial characteristics (a max , M w
and R) for a “design basis” earthquake for use in design of an 2 to 3-story
apartment complex and shopping center in Charleston.
• Using your Equal Hazard Spectrum for 2% in 50 years, and the deaggregation,
recommend the approximate initial characteristics characteristics (a max, M w
and R) for a “design basis” earthquake for use in design of a major earth dam
(with a crest height of approximately 350 feet, and a predominant period of
about 0.8 seconds) near Charleston.
Part II:
3. Find the location where you live (while attending U. C. Berkeley.) Again, find the PGA, and
the S A values for T = 0.2, 0.3 0.5 and 1.0 seconds, and plot the Equal Hazard Spectrum (5%
damped, elastic) for a probability of exceedance of 10% in 50 years (the presumed UBC
building code level.) On the same figure, plot the actual response spectrum from the current
UBC for Site Class C conditions. (Don’t forget to apply the near field factors if appropriate.)
Does this worry you? Remember, if your building is more then about ten years old, it was
probably designed for even lesser levels of shaking.
Part III:
Now, on your own volition, and despite a rigorous schedule of competing priorities and
conflicting assignments from other courses, access another web site (still under construction)
sponsored by CDMG at http://www.consrv.ca.gov/cgs/, and explore a bit. This site is dedicated
more locally to California, and presents similar information to that presented by the USGS site,
but it is not yet as well along.
4. Repeat the First part of Question #3 above. Is the strong shaking hazard mapping of this site
the same (same basis, and same values) as the USGS site? (Don’t spend a long time on this
one….just make a few quick checks.)