a reply to: CreationBro
Okay, moving on to your quite detailed prediction of a California quake.
March 2017 on a wednesday (March 29, 2017 7:00-8:00 am)
Magnitude 7.3 - 8.5
Epicenter San Mateo Burlingame Millbrae area
Devastating damage to high rises and bridges in SF downtown
Billions of dollars in damages, worst natural disaster in us history?
You have been very specific with date, time, location and magnitude. It's pretty rare to see that much information given so precisely, so I thank you
The magnitude range you have cited: those are very scary numbers. The April 18, 1906 San Francisco quake (which was a Wednesday, as it happens) is
estimated by UC Berkeley to have been around a mag 7.7 - 7.9 Mw. (Viz their 1906
A note for readers: "Mw" is the notation for the Moment Magnitude scale, which is the most common standard used today and for the past few decades for
larger events. The reason for its use is that it is more precise with larger quakes than the "Richter Scale" that MSM journos still
all the time, even though in the vast majority of cases with bigger quakes, the Richter is not
the scale actually used by USGS or almost anyone
else when they publish their data.
I am suspecting you (CreationBro) are aware that there is a very big difference between a mag 7.3 and an 8.5, but for readers who might not know, as
modern earthquake magnitude scales are logarithmic, even seemingly small differences can be very significant.
For example, let's consider the lower-end estimate for the 1906 SF quake, at mag 7.7 Mw, compared with your low-end figure for the predicted quake as
mag 7.3 (with Mw assumed for your figures).
A magnitude 7.7 Mw quake is 2.511 times bigger than a mag 7.3 Mw in terms of shaking, but 3.981 times stronger in terms of energy release. In other
words, though the magnitude difference is "only" 0.4, it would take almost four mag 7.3 quakes to release the energy of one mag 7.7 quake.
Anyone who wants to check these figures can use the on-site calculator at USGS. Just go to their
How much bigger
page then click on the blue "Try It Yourself" Calculator,
which will open a new window with the calculator all set up.
So, with your range of 7.3 to 8.5, we get:
A magnitude 8.5 Mw earthquake is 15.848 times bigger (shaking) than a mag 7.3 Mw, but is 63.095 times stronger in energy release.
Thankfully, magnitude 8-plus quakes are very rare. We average less than one per year, world-wide. But also, in the case of the San Andreas Fault
System, I've not read any studies by experts that suggest an 8.5 Mw is possible there. They believe the fault system simply does not store up that
huge amount of energy. It's a strike-slip fault and they tend to let go well before then. I did read a report a few years ago that suggested a low mag
8 Mw was possible. Not an 8.5, but perhaps up an 8.2. Even so, that would be a horrific event.
However, scientists and other experts are not always right. There is still a level of very informed guesswork involved.
The other factor here is location. Studies have shown that the fault tends to let go in sections, with each section having a big quake about once
every 150 years or so. The last really major quake in the southern section of the SA fault was in 1857, so it's more likely that part could let go
with a really substantial quake, even pushing around a mag 8 Mw.
The Bay area section of the fault, on the other hand, having had a big quake only 110 years ago (okay, almost 111 years), has probably not built up
enough to produce a quake that big. But it could still get into the low to mid 7 range, which would fit with your lower-end prediction of 7.3.
The worry is if the southern section lets go in a big way, it might make the "Bay" section (and north of it) go as well. That would be a very bad day
indeed. It wouldn't make a Bay region quake bigger, because quakes just don't really work that way: it's localized energy release, not transfer of
energy from another place. But it would create problems with infrastructural failures over a much larger area than if "only" one section let go. This
would make it harder to bring emergency personnel and resources into the hardest-hit, densely-populated areas from outlying regions.
Re the suburbs you mentioned as possible epicenter locations: they are all right by the fault where it runs down through the peninsula, so they are
not without likelihood.
Damage: Fema / Homeland Security have done studies for these kinds of events, and also for a CSZ event (which would be far, far worse than a San
Andreas fault quake). On the plus side, a lot of buildings in the Bay area have been retrofitted to make them more secure in a major quake, and ditto
a lot of the transport infrastructure's key components. However there would still be structural collapses, damage to rail and tram lines, bridges and
interchanges, power outages, water and gas main leaks/breakages and so on.
On of the main concerns would be fire, because with many water mains out of action, firefighters would struggle to contain outbreaks -- even assuming
they could get their trucks on-site in the first place. So, while the next "big one" in Cali might not match Katrina in terms of total $$ losses, it
could still be well up there.
edit on 8/3/17 by JustMike because: (no reason given)