Valencia, California
UntilTaxi
the area is like in terms of seismic activity. Any information would be
greatly appreciated! Thanks!
Taxi
Berton Corson
Valencia is just north of where the Sylmar quake struck in 1971, and about
15 miles or so northeast of the Northridge quake. It is also southwest
of the San Andreas Fault. From these points, it looks like Valencia is
surrounded by quake activity, but no one can make an accurate prediction
of whether an area that has had lots of quakes nearby won't get any more
soon (you've used up your quakes) or whether not getting a quake in a
100 years means your do for one. I've seen posted here that statistics
are rather strange, and may mean nothing if a 8.0 quake happens tomorrow.
But, in all, we live in an area that gets earthquakes, and whether a
big one will happen tomorrow in Valencia no one can tell you, but there
willl for sure be more earthquakes. At least, Valencia is a relatively
newly developed area, so the building construction should be more safe
to withstand a major quake, than other older areas of Los Angeles County.
Inovative Graphics Solution
> At least, Valencia is a relatively
>newly developed area, so the building construction should be more safe
>to withstand a major quake, than other older areas of Los Angeles County.
>
Unfortunately, as was learned in the Northridge Quake, the current building
codes only allow for slip strike type quakes with side to side reinforcing.
Blind thrust quakes, like the Northridge quake, produce a violent up and down
motion subjecting the buildings to several times their own weight, a stress
for which the current codes make no provision and for which many buildings were
NOT built.
Berton Corson
> Unfortunately, as was learned in the Northridge Quake, the current building
> codes only allow for slip strike type quakes with side to side reinforcing.
> Blind thrust quakes, like the Northridge quake, produce a violent up and down
> motion subjecting the buildings to several times their own weight, a stress
> for which the current codes make no provision and for which many buildings were
> NOT built.
At least being 1/2 safe is better than being not safe at all. In any
event, I live in Nortridge, several miles north of Northridge Fashion
Center. The house did survive with minimal structural damage (mainly
cosmetic cracks and the fireplace needing replacing) and I guess did
pull through OK, in regard to vertical seismic waves.
Linda Phillips
Valencia is in the Santa Clarita Valley, which was affected by the
Northridge quake. Most of the Southern California area is on or near
faults -- we live with that fact and, as the previous responder said,
homes are mostly constructed to deal with quakes.
Steve Salyards
g915...@huey.csun.edu writes:
>Valencia is just north of where the Sylmar quake struck in 1971, and
about
>15 miles or so northeast of the Northridge quake. It is also southwest
>of the San Andreas Fault. From these points, it looks like Valencia is
Add to this that trenching 8-10 years ago in Newhall (just north of
Valencia) found motion on the San Gabriel Fault in the last couple
thousand years.
Steve Salyards
saly...@euridice.ess.ucla.edu
Southern California Earthquake Center @ UCLA
Glen Blankenship
> codes only allow for slip strike type quakes with side to side reinforcing.
> Blind thrust quakes, like the Northridge quake, produce a violent up and down
> motion subjecting the buildings to several times their own weight, a stress
> for which the current codes make no provision and for which many buildings
> were NOT built.
As was pointed out in this very newsgroup not long ago, the nature of the
fault (slip-strike vs. thrust) has very little to do with the vertical
vs. horizontal accelerations experienced by buildings in the surrounding
area.
In fact, the mixture of horizontal and vertical accelerations in the
Northridge quake was quite typical, and varies tremendously from one
location to the next. Trying to predict the direction of acceleration
from the orientation of the fault is rather like trying to predict
the oscillatory direction of an incident sound wave produced by a
hand clap based on whether the palms of the hands were held upright
or flat. There is no simple correspondence.
The building codes do make allowance for vertical accelerations, but
in the past it's been assumed that the safety margins inherent
in the code requirements for vertical loads (both the dead load of
the structure and the live loads of furnishings and occupants) would
be sufficient to handle the live load produced by the vertical
accelerations of an earthquake.
Lateral accelerations require special additional engineering, since,
outside of earthquakes, most structures never experience large lateral
loads. Even the wind loads encountered by large high-rises are orders of
magnitude less than the lateral loads that can occur in even a moderate
earthquake.
What the codes underestimated was just how high the vertical accelerations
might get. What *was* unusual about the Northridge quake was the duration
of the event. The unexpectedly rapid release of energy resulted in much
higher levels of acceleration (both vertical and lateral) than the models
had predicted, and that the building codes, therefore, were prepared for.
But none of that has anything to do whether the fault is slip-strike or
thrust. Such accelerations are just as possible in a slip-strike quake,
and the codes will just have to be revised to reflect that.
---
Glen Blankenship
obo...@netcom.com
g.blan...@genie.geis.com