
M 7.1 SoCal Earthquake: What's Next? - mgsouth
http://temblor.net/earthquake-insights/m-7-1-socal-earthquake-triggers-aftershocks-up-to-100-mi-away-whats-next-9055/
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needle0
One thing I noticed is that when the US talks about earthquakes, it often only
notes the seismic magnitude value of the quake and doesn't always mention the
seismic intensity scale values of the affected locations. This is in contrast
to Japan where quakes are almost always mentioned in both magnitude and the
Japan Meteorological Agency's "shindo" intensity scale [1], eg. "The 2011
Tohoku Earthquake was a M9.0 quake with a maximum intensity of shindo 7." The
US does have the equivalent of the JMA shindo scale - the Modified Mercalli
(MM) scale [2], and they do seem to be used, but I see the MM values mentioned
much less frequently than how both the Japanese agencies and the general
public refers to shindo values.

While the magnitude value signifies the overall energy of the quake, intensity
scale values indicate the shaking intensity of a given location; hence, it
feels more grounded in one's daily life experiences. Many Japanese individuals
have developed an approximate sense of how strong a quake is - conversations
like "That was a bit big, somewhere around shindo 4?" are common after quakes.
People do of course care about magnitude, but the thing they care most about
after a big quake is more likely "what was the seismic intensity in the worst-
hit area?"

Any idea why intensity scales seem to be much less common in the US?

[1]
[https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_se...](https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_seismic_intensity_scale)

[2]
[https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_sc...](https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_scale)

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abcanthur
I haven't lived in seismic areas much, but I was in central LA for both of
these quakes. I was hoping for a simple Richter*distance (or d^.5, whatever
may be appropriate) value to be reported. I realize that real effects are
multivariate, but wouldn't that at least provide the maximum possible effects
to report a magnitude-distance metric? Bc for a few million people I think the
quake felt like a strong spin cycle in the next room , but we were told it was
the biggest in decades.

~~~
Gibbon1
Yeah really depends one distance and local conditions. And sometime 'micro'
local conditions.

Friend of mine that lived in Oakland during the 89 earthquake mentioned seeing
a 'line' of damaged buildings that snaked through a neighborhood. One or two
houses on a block were wrecked. The houses across the street were also
wrecked. Houses next to them were fine. Go the next street over same thing.

He thinks that line followed an old creek bed that developers filled in. So
those houses were built on mud overlain with poorly compacted fill. During the
earthquake the mud liquefied and sloshed around and the fill settled.

Flip side, friend in the Santa Cruz mountains a couple of miles from the
epicenter. His house is built on top of a hard shale outcrop. His house
suffered no damage at all.

~~~
DrScump
The weakness of poor fill was also demonstrated by the collapse of row houses
in the Marina district of SF.

One striking effect was the _directionality_ of the damaging waves. Bookcases
and such that were perpendicular to the waves from the hypocenter went over;
those that were parallel were fine.

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wanderfowl
The writing and research following this quake series has again underscored for
me both a) how little we actually know about predicting earthquakes b) and how
frustrating that is. You can read every article out there about the things,
and each one ends with, roughly, _shrug_. As somebody who derives a sense of
control from knowledge, it's extra terrifying to have something with such a
huge potential impact on me completely in the dark.

~~~
lotsofpulp
I don't see the point worrying about things outside of your control. Solar
storms, nuclear war, infectious diseases, asteroids, any number of other
unknown natural phenomena we know nothing about. Mitigate what you can, try to
help others, but accept that at the end of the day, you (and the rest of
humanity) are most likely inconsequential in the story of the universe.

~~~
themodelplumber
I'm just a casual ham radio operator, military history hobbyist, amateur
health science researcher, and I know a tiny bit about space. But it seems the
four types of disasters you mention have been studied and measured in depth,
with the result bring great impact on our vulnerability to them. Is this not
so, and should we not continue improving our measurement (control) systems?

~~~
lotsofpulp
We should strive to improve our model of the universe, but I was specifically
responding to the notion of being “terrified” by the person I responded to. I
think am not terrified by it because I’ve accepted that there are always any
number of risks that can wipe me out, known and unknown.

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rubicon33
You conclude that infectious disease is "out of your control"?

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coding123
> I’m saying no point in being worried about it.

(sorry there is no reply option for lots of pulp).

Isn't worry the one human emotion that actually makes us ready for things. If
we had an earthquake 1000 years ago that killed half of society and the people
just said, damn oh well. They don't do things the same way after that do they?
They change design, learn more about the planet, adjust adjust adjust. All of
that is driven by worry.

~~~
lotsofpulp
Perhaps worry is not the right word, as the person I initially responded to
had used the word “terrified”. As in I wouldn’t dwell on things out of my
control.

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ianai
The scale of geological time never ceases to impress:

“There was plenty of accumulated stress, enough to permit a quake with 3 m (10
ft) of slip. That suggests that one can, indeed, have aftershocks 150 years
after very large mainshocks”

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mc32
What I don’t get is how is a quake which happens on a disconnected and
different fault (heretofore unknown) an aftershock of a previous quake (which
occurred over 100 years ago)?

I looks like quakes are on a continuum. The extremes are, each quake is an
individual event; on the other all quakes are a result and continuation of
previous quakes. It seems like the slider position on the continuum is up to a
bit of “interpretation”.

~~~
hvs
As a person that knows nothing about this subject, that's the impression I got
as well. The tectonic plates are constantly moving, so of course earthquakes
in one place will often cause stress in another place. Understanding this
process is certainly important, though.

~~~
ianai
I think it’s closer to being a constant chain of reactions than otherwise -
because the earth has so much heat and magma below its crust.

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coss
I live in SoCal and can't believe the amount of attention this has gotten,
literally world wide. Am I underestimating the importance or is it just a slow
news cycle?

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olivermarks
'...nothing at the ground surface had given this fault away before it fired
off the quake. Some of the world’s best field geologists had scoured this area
for the past 50 years...'

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phy6
If you can don your anti-quackery bio hazard suit, the youtube channel
Dutchsinse is entertaining for his forecast of earthquake locations. His
guesses involve following trends along tectonic boundaries on a globe scale.
One of the things I've heard him say that I've not heard elsewhere is the
implied correlation between geothermal pumping operations near the latest
epicenter and crust weakness.
[https://www.youtube.com/watch?v=Oj6Vj4TOtx4](https://www.youtube.com/watch?v=Oj6Vj4TOtx4)

~~~
thanatos_dem
Eek. The content is interesting, but the channel’s style and sound effects are
just too much for me. Same problem I have with “Mad Money”.

~~~
phy6
I agree, too much VHS-iness.

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caymanjim
I can't speak to the merits of this article, but the tone is a bit
sensationalist, especially the conclusion, and then they link to some
commercial entities to help you prepare for doom. It makes me dismiss the
entire article as a fear-mongering advertisement.

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peter303
Interesting a non-peer-reviewed study is released quickly on web.

However Dr Stein is one of my Stanford classmates and computing earthquake
stress changes for 30 years. So I would believe this study.

