Leon lcb11211@swbelldotnet writes:
On 4/21/2017 7:54 AM, Scott Lurndal wrote:

I've experienced two major earthquakes (Wittier Narrows, Loma Prieta)
and a few minors (Napa a few years ago). For the most part, the damage
is localized (similar to a tornado, more localized than a hurricane). For
Wittier narrows, I was living about 7 miles from the epicenter and it
did no damage to my home, and very little at my office. With the Loma
Prieta the total damage ($5billion) was less than katrina ($108 billion)
even when adjusted for inflation.

I'll take the earthquake anyday. The risk of an 8+ is much lower than the
risk of a F5 tornado or a cat IV hurricane.


Well that sounds like sound reasoning. With news reports we "out
siders" often see repeated broadcasts of the same areas and do not
always realize the repeat scenes. We tend to think that California is
hanging on by a thread. LOL

I was under the impression that big quakes were as devastating as a
direct hit Cat 3 or larger hurricane.

It depends on a number of factors, including soil conditions, magnitude, location
of epicenter, and age of buildings. Since 1906 cleared out a big part
of SF, much of the construction there is newer. After 1934 long beach,
construction standards were updated, and were changed significantly after
1971 sylmar[*]. The Loma Prieta quake, which was epicentered some 60 miles
south of SF, did little-to-no damage to the peninsula/south bay which is much closer
to the epicenter, but did significant damage to the marina district in
SF which is built on land filled in in the late 19th and early 20th
centuries. It also pretty much destroyed highway 17 (now I880) through
oakland, which was a double decker freeway built before sylmar where
the top deck collapsed on the lower deck. Known as the Cypress Structure,
this was also built on soft soils near the bay.

Note that after the Northridge quake (which mainly affected soft-structures
like apartment buildings built over parking bays) when some overpasses on
I10 collapsed, they were rebuilt within 12 months.

With modern building code standards, and common earthquake awareness by
residents (secure tall items to the wall, hang heavy items using appropriate
hardware, secure overhead cupboard doors with latches), the chances
of damage from a moderate quake are fairly low outside of certain soil
types (e.g. liquifaction).

A massive quake (e.g. 9+), all bets are off, but they're extremely rare,
and given the recent history of the San Andreas, there is not enough
energy accumulated for a really large one here. I'd be more worried
about the faults in the strait of Juan de Fuca which is due for a big
one likely including a large Tsunami clearing out many of the islands
in the sound, plus parts of Seattle - predictions are of a 15% chance
of a 9+ in the next 50 years. Plus/minus some large error bars.
[*] One of the Mission Impossible TV show episodes was filmed on the ruins
of the VA hospital that collapsed in the Sylmar quake in 1971.