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RE: ibc 2000 adoption

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Actually, the Great Alaska Earthquake of 1964 was not recorded. It had an
estimated Richter Magnitude of over 9+. Estimated high intensity ground
shaking was over 90 seconds. Anecdotal reports by survivors estimate the
ground shaking at over 3 minutes.

The focal point was in Prince William Sound in a known subduction zone. The
focal point was deep. The ground shaking effected most of South Central
Alaska from Kodiak to Yukatak, and north into the Talketna Mountains.

The mechanism for this earthquake is similar to the Nisqally event in
Washington, both being deep subduction zones and effecting large
geographical areas.

We are really talking about three types of seismic events. Near surface
shallow events from local faulting, deeper events in the 30 km range, and
major events in the plate contact (RM = 9+).  

-----Original Message-----
From: Yousefi, Ben [mailto:Ben.Yousefi(--nospam--at)]
Sent: Thursday, March 08, 2001 4:06 PM
To: 'seaint(--nospam--at)'
Subject: RE: ibc 2000 adoption

Excuse my ignorance, but wasn't the largest recorded earthquake in North
America centered near anchorage? And it is in SDC "D" !! this is amazing.
Probably one of the most idiosyncratic shortcomings of the 2000 IBC is its
over reliance on the minutely defined seismic acceleration contours. The
IBC's maps assume we have a tremendous knowledge of the geologic hazards of
what's below us. Whereas, almost none of the major earthquakes in recent
memory (Northridge, Kobe, etc.) occurred on previously known faults. 

In my humble opinion the current seismic zones, although a crude method,
along with the near faults effects, are still the best system of
categorizing the seismic hazards in general. (incidentally, most of San Jose
will also be in seismic Design category D!)

Ben Yousefi, SE
San Jose, CA

	-----Original Message-----
	From:	Haan, Scott M. [SMTP:HaanSM(--nospam--at)]
	Sent:	Thursday, March 08, 2001 9:11 AM
	To:	'seaint(--nospam--at)'
	Subject:	RE: ibc 2000 adoption

	The Municipality of Anchorage, Alaska is almost done adopting the
2000 IBC.
	There have been very few proposed amendments that have been approved
by the
	code adoption committee.  Anchorage will always be Seismic Design
Category D
	because S1<.75 and SD1>=.2 always, SDS>=.5 always.  See Table
1616.3(1) and
	Table 1616.3(2).

	The one notable amendment is that the perforated shearwall
	outlined in the draft 2000 NEHRP Recommended Provisions will
continue to be
	accepted.  Want a free copy of an example perforated shearwall or
	seismic plan check Excel spreadsheet?

	The IBC seismic provisions are less ambiguous and have fewer typo's
than the
	UBC did.  Once you figure out the way the IBC is laid out, the
	provisions leave less to the imagination.  My only gripe is that
almost all
	of the material chapter stuff is in separate $100+ books.  

	The State of Alaska has adopted the architectural IBC provisions and
	discussing the structural provisions.

	Scott M Haan  P.E.
	Plan Review Engineer
	Building Safety Division, 
	Development Services Department,
	Municipality of Anchorage

	> -----Original Message-----
	> From:	dadie(--nospam--at) [SMTP:dadie(--nospam--at)]
	> Sent:	Thursday, March 08, 2001 5:14 AM
	> To:	seaint(--nospam--at)
	> Subject:	ibc 2000 adoption
	> just wondering how building officials are adopting the ibc 2000 in
	> non ubc districts.  are they adopting in with major additions /
	> /
	> revisions / amendments - or are they pretty much adopting it as
is?  are
	> there local restrictions on how "bad" a seismic category can get?
	> tia
	> da