The big one. A major earthquake on the
San Andreas Fault often exaggerated in
movies, but a real danger to Southern
California. Nothing like what you see
here, of course, and computer models
suggest it would actually be even less
of a threat to us in our corner of the
state. For San Diegans, the Rose Canyon
Fault system running through our most
populated areas, is the bigger concern.
Though it hasn't had significant
movement since European settlement, it is
considered active and has potential for
a magnitude 6 or 7 quake. There's a new
park on the eastern edge of downtown
that owes its existence to a section of
this fault.
Dr. Pat Abbott, geology professor at San
Diego State University, recently took the
director of the County's Office of
Emergency Services, Holly Crawford, and
assistant director Stephen Rea on a tour
of the fault, which begins here at
Faultline Park. "so members of the public
might see that there's a fault obviously
running right through this park and then
this huge high-rise building.
What would you expect if you were maybe
in the top of this building as opposed
to one of these lower buildings across
the street?" "Well, you know it's interesting
because buildings have periods or
frequencies of movement just like
seismic waves do. Now right here on this
fault
that's kind of seismic waves are going
to be getting of the real high frequency
sorts of things and they don't really
bother the tall buildings like this that
much. These kinds of seismic waves are
going to shake that building - that's the
San Andreas Fault, east of the Salton Sea.
When that comes in with those rolling
kinds of waves like we had on Easter six
years ago,
that's going to make that building - oh
boy, that'll be quite an experience. Not
for danger, but just I mean you're going
to get a ride that you'll remember for
the rest of your life." If the Rose Canyon
fault goes the big concern is the older
unreinforced buildings and a newer
building's heavy objects falling on
people.
The proximity to the physical fault line
is not as much of a concern, which is why
we still see new buildings going up
downtown. "You know here's another one of
these urban fault parks. We're here at
First and Market Street and this little
nice little tree-field park running
between these buildings on this diagonal,
this is another active fault that people
have - we cannot build on top of it
because when the ground ruptures it
would break the building; but you know
interestingly enough,
you know when we look at the
balconies you say well golly look people
are living right here right next to the
fault isn't that more dangerous?
No, no it's not. It doesn't really matter
whether you're 50 feet or five miles
away consider that the fault ruptures at
eight miles depth and the earthquake
waves come straight up
it's about the same whether you're five
miles away your right next to it. Kind of
what's intuitive actually is not a not a
problem, being closed is not a problem."
Moving out of downtown, we journey to the
spot with a Rose Canyon Fault system
first meets land in San Diego, just off
the coast of La Lolla - a spot where you
can see physical evidence of the power
of an earthquake fault.
"well we've come here to these beach
cliffs in La Jolla Bay to view where a major
fault comes on shore. You know, if we were
up there in Orange County now, there would
be the Newport-Inglewood Fault. In 1933,
the Long Beach earthquake, 115
people dead, that exact same fault
up there
here it is coming ashore in San Diego
and it's beautifully shown in these
cliffs behind us here. This is part of
the Rose Canyon Fault system.
This one's called the Country Club Fault,
but it's part of the Rose Canyon Fault
zone and you can see two very different
types of rocks juxtaposed against each
other. When we look at the rocks over
here on the east side of the fault, we
see sandstones interbedded with a lot of
mudstones, tilted a bit here by the
fault action, but a lot of layered
sedimentary rocks, mostly mudstone. If we
swing around to the other side and look
at the other side of the fault here on
the westside, massive, thick sandstone
bed, totally different rock layers.
Here's the actual slippage along the
fault surface. These rocks had moved
maybe even as much as half a mile. Many,
many, major earthquakes occurred to
separate these rocks. This isn't a one-time
event. This is big earthquakes over and
over and over again. These are landscape
shaping events. Faults like this are the
reasons why we have Mount Soledad, if
it wasn't for these faults, there would be
no Mount Soledad - the whole landscape
would be flat." In fact following the fault
over Mount Soledad and down Interstate 5,
we come to Tecelote park, where
tucked into the back corner of the
baseball fields, there stands a direct
acknowledgement of this fault,
perhaps the only one in the city. "We hear
so much about the San Andreas Fault and
I talk to people all the time who have
never even heard of the Rose Canyon
Fault and, you know, part of it might be
due to the fact that we don't alert them
or show them where that fault is."
"This area right here,
it wouldn't surprise me today if it
started moving down by the Coronado
Bridge, came through downtown, Old Town,
here up to Mount Soledad, a 15-mile
length, 6.4 magnitude earthquake, roughly
speaking, could happen today without any
trouble whatsoever. On the other hand, it
might be 200 years away, but that's the
part we don't know. As harmless as
this looks, this is a killer right before
your eyes."
So as we wait for that quake, back where
we started at Faultline Park, you can
visit a public art project that will
help you keep an eye on any movement on
this fault, however small, "I really like
this installation here Fault Line Park,
this big sphere with a viewing tube right
through the center, goes across the
active fault and lines up with the
sphere over there. If you look through
the center of this sphere, here, the idea
is well, when the fault moves the spheres
will no longer lineup. And, you know, this
is a great art installation, but
we geologists have been doing this for
over a 150 years, planning
instruments on either side of a fault to
try to catch the creep movement that
takes place or the amount of total
offset in a big earthquake, so here's art
imitating science." So if all this
earthquake talk has got you motivated to
prepare yourself for a disaster, visit
readysandiego.org. Run by the
county's Office of Emergency Services,
the site provides everything you need to
get yourself ready for a natural
disaster that, hopefully, is many, many
years off. In the County News Center, I'm
Dominic Fulgoni.