The original message was too long, so I divided it
in two, and removed the attachment...
Part I: Happy
I just came from the Paso Robles Area where I was inspecting
damage after the recent earthquake. Here are some observations from the
Several newer - and quite expensive - houses sustained
substantial cosmetic and even some structural damage which I would not
expect from such structures. Generally it proved to me that
drywall and stucco shear walls should not be used - especially in
irregular houses - no matter how low the calculated forces/stresses
I also observed distinctive soil damage that I did not
see a lot during Northridge. In one instance, a three-car
garage, separated from the main house by a breezeway, visibly settled more
than 1 inch (without any substantial damage/distortions inside
it!). The garage was obviously built on fill while the house proper
had a sub-grade level with retaining walls. Strangely, the house is
about 15 years old, and never had settlement problems (no noteworthy old
cracks in stucco).
The other case was even more amazing - a 3000 sq. ft
one-story house on a flat lot on top of a hill (as many of them are in
that beautiful country, imagine the view). The house sustained very
little - barely any - damage to the superstructure, in spite of heavy tile
roof, brittle finishes, and irregular shape/composition. But the
slab it was built on cracked intensively - long linear cracks in, and under,
ceramic floor tiles. Some of the cracks have vertical offsets up to
There was some evidence of topsoil fissuring
and distortion/shifting of the underground pipes; a large
swimming pool had drained since the earthquake (in 7 days).
It looks as if the apparent underlying rock-like
shale was shifting along its weak planes... Can it happen that way?
And if so, why so little damage to the
To illustrate the force of that earthquake: a crew-cab F150
was parked in the garage (naturally, a 10-car garage). The sectional
door is now bent and would not open - apparently, because the truck was
slammed against it from inside, and then was pushed back (~36" amplitude
movement). All that is verifiable by clearly visible tire marks on
the garage floor.
Also, it was nice to see the tower in the downtown Paso
Robles already replaced with a wood-framed OCB-sheathed one. BTW, a very
neat job, and, obviously, much safer structure (attached)... I presume it
is the one that collapsed and was in all news.
Other than that -
Happy, Healthy, Peaceful,
and Prosperous New year to all.
Steve Gordin, SE