[CEUS-earthquake-hazards] Question-

[Joe Tomasello]

Lawrence, Laurence, et al:

When I started this I was actually responding to Lawrence Goldfarb's
comments dated February 26, 2008, but will try to tailor them in an effort
answer to Laurence Wright's questions.

In my opinion Goldfarb's comments assigns juxtaposition to earthquakes,
floods, tornados and FEMA trailers that simply isn't there.  Each natural
disaster has a distinctly identifiable signature and footprint. Floods
inundate the land pushing over and undermining the built environment,
staying within certain geographical confines. Tornados and other wind
related disasters lift up and push over the built environment, cutting fine
lines of disaster. Hurricanes are a mixture of wind related disasters and
tidal surge flooding. Earthquakes, like the others, have distinct
signatures; shaking the stew out of the built environment, more so at the
epicenter with destruction proportionally reduced by the distance from the
epicenter.  And finally, FEMA trailer disasters are.well they're FEMA
trailers.
  
In a roundabout way I'm pointing out that earthquake damage is different
from flooding or hurricanes and the resulting damage footprint will be
different.  A good example is the Northridge event. The 1994 event was
centered within the San Fernando Valley populated by approximately 3
million. The major damage occurred within 10 miles of the epicenter with 57
fatalities.  Records indicate that about 1,600 where hospitalized, 22,000
were treated and released (less than 1% of the population).  Approximately
125,000 were temporarily or permanently displaced (less than 5% of the
population).  Roughly 6% of the 66,546 buildings inspected were severely
damaged (red-tagged) and 17% were moderately damaged (yellow-tagged).  Or,
another way to look at it , 3% of the total number of residential units
necessary to support the population were damaged to the extent that they
needed to be repaired or replaced before they could be re-occupied.  Of
significance was the number of soft-story low-rise (3 and 4 stories)
apartment buildings which collapsed causing the majority of the fatalities -
an issue that could be easily addressed by seismic regulations written
around 10% PE maps.  Damage in the outlying areas (beyond 10 miles of the
epicenter) was, generally, less severe so as not to require building
inspections. As I noted in previous e-mails less than 8% of the hospitals in
the Los Angeles area were evacuated and no fatalities were reported as a
result of a hospital structural failure; in fact most evacuations weren't
related to structural damage, rather to mechanical equipment failures.  One
report stated that, "buildings designed and constructed in accordance with
modern (mid-70's or later) seismic requirements performed well
structurally." In a very general sense, to the structural engineer, the
implication is that buildings designed with a lateral force resistance will
provide a semblance of life safety. 

An earthquake in any given region doesn't mean that every building falls
down or becomes uninhabitable.  However in the case of an hurricane, such as
Katrina this can be the case over hundreds of miles of coast line. You can't
compare the two except to say they are both disasters. 

Regarding Wright's question as to which set of hazard maps to use
considering a blood bank, I'd suggest using the 10% Probability of
Exceedance maps. If an earthquake were to occur, these are the most likely
ground motions to be seen within the building lifetime.  However, the user
still needs to assess his risk and the exposure to that risk.  If finding a
need to function after any earthquake event is critical I would magnify
those loads through the "importance factor."  In the same breath, if the
facility is considered to be significantly critical, I would also look more
closely at effects from tornados, flooding, and terrorist attack. 

This firm was involved in a County wide 911-Call Center where this was done
(in this case the 2% PE maps were used at the request of the user). The
facility was just short of being a regional emergency management command
center. The cost outstripped the budget by a considerable margin and was
shelved - I understand the county is still looking for additional Federal
funding.  Another surprising issue that surfaced was finding room to store
food and water for the occupants over a short period of time - you'd be
surprised at the volume required inside the protected area.  I used DoJ's
"Assessment and Strategy Development Tool Kit" to rank the various hazards
and threats for a mitigation program. Looking at a similar situations I'd
suggest the following:  http://www.ojp.usdoj.gov/odp/docs/assessment.pdf