
Tsunami alert as Chile hit by powerful earthquake - hanoz
http://www.bbc.co.uk/news/world-latin-america-34275783
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rndn
As always, TheEarthquakeGuy provides clear and up-to-date information on
Reddit:
[https://www.reddit.com/r/worldnews/comments/3l8fse/79magnitu...](https://www.reddit.com/r/worldnews/comments/3l8fse/79magnitude_earthquake_strikes_off_the_coast_of/cv43rw0)

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msm23
Their live thread is here:
[https://www.reddit.com/live/vlfanix4u5u8](https://www.reddit.com/live/vlfanix4u5u8)

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cossatot
The hypocenter (location underground where the earthquake started) is fairly
deep (~26 km according to the USGS) so hopefully the rupture didn't reach the
surface (it's ambiguous but maybe 30% likely for an earthquake of this size
with a hypocenter at that depth). If it didn't, then the likelihood of a
damaging tsunami is far less because there isn't a big displacement at the
seafloor.

Interestingly, from the location it looks like it's right at the northern edge
of the rupture patch of the 2010 Maule earthquake (8.8), which was at the
northern end of the 1960 ~9.4 earthquake (biggest on record). These earthquake
rupture patches are visible here[1]. The idea is that as the oceanic plate
subducts, the upper part of the subduction zone/fault/megathrust is locked,
i.e. the upper and lower plates are stuck together above 20-30 km, and elastic
stress and strain accumulate slowly. Then, this stress and strain is
sporadically released as earthquakes, but these don't rupture the entirety of
the fault. Instead, they happen in patches but an earthquake on one part of
the fault adds more shear stress to the adjacent parts of the fault that
didn't rupture. This basically steps the clock forward on the adjacent part,
so it ruptures next. In this way, the displacement accumulated along a big
fault over centuries or millennia is released in a relatively shorter
timespan, then a long period of quiescence sets in.

That's a theory, anyway, and it's almost certainly right in some places, some
of the time.

A big research question for some (not necessarily funding agencies) is
figuring out whether the shear stress released in these big earthquakes is a
big or a small part of the accumulated background stress (stress is nigh
impossible to measure directly). If most of the shear stress is released,
it'll be a long time before another earthquake can occur on a given fault
segment, but if only a little bit is released, then the potential energy is
still there for another earthquake and it can happen again quicker than the
full plate reloading time. From a statistical perspective, a full stress
release may correspond to periodic earthquakes while a partial release may
correspond to a more random (i.e. Poisson) recurrence pattern.

If anyone is interested in this stuff, let me know here or email me (in my
profile) and I can try to write up a blog post with it, and maybe with some
Monte Carlo simulations to illustrate.

[1]: ftp://ftp.ingv.it/pub/alessio.piatanesi/PAPERS/2011_NGEO_Chile.pdf

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sillysaurus3
I am interested in this stuff. A blog post with Monte Carlo simulations sounds
cool!

(EDIT: I don't normally do this, but... At least 6 other people agree. Sounds
like you'll have an audience!)

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JoshTriplett
Sorry, I unintentionally downvoted this when I intended to upvote it. I'd like
to see this as well: a demonstration of how the available data gets analyzed
to produce both models and predictions.

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henpa
I live on a 11th floor apartment in Sao Paulo, Brazil (near Av. Paulista), and
I felt this quake very slightly! It was very subtle and I thought first that I
was just feeling dizzy or something. Then I searched for "terremoto"
(earthquake in spanish) on Twitter and then I found a bunch of posts. Isn't it
crazy that I could feel this from over here?

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sobinator
Earthquakes, and the twitter responses to them, have been the focus of some
pretty interesting academic studies that I've read (2011 Christchurch, NZ was
what I studied). If I still had access to the academic journals, I'd pull up
some articles. They present fantastic case studies of how using twitter user
lat/longs, time logs, and nlp can be very useful.

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ngoldbaum
When I lived in California I would often do a twitter search after feeling a
small earthquake. If there weren't any results, I would usually assume it was
a truck passing by or something like that.

Very often there would be tweets about the earthquake several minutes before
the official USGS page for the earthquake was created.

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Scoundreller
USGS Event page here:
[http://earthquake.usgs.gov/earthquakes/eventpage/us20003k7a#...](http://earthquake.usgs.gov/earthquakes/eventpage/us20003k7a#general_summary)

Edit: Magnitude 6.4 aftershock event page here:
[http://earthquake.usgs.gov/earthquakes/eventpage/us20003k7w#...](http://earthquake.usgs.gov/earthquakes/eventpage/us20003k7w#general_summary)

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Scoundreller
Not a bad idea to setup an email alert at the USGS Earthquake Notification
Service for your area if you're in a coastal location:

[https://sslearthquake.usgs.gov/ens/](https://sslearthquake.usgs.gov/ens/)

(or if you're not and want to get news of this kind of thing sooner)

Has anyone created an app that checks against your phone's GPS location
automatically?

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deepuj
Signed up, and even an hour later haven't got the confirmation link by email.
Not very reassuring for an 'Earthquake Notification Service'.

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darkpore
Same here...

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crorella
A video from ~600KMs south of the epicenter.
[https://twitter.com/jorge_cerda_/status/644284954923417605](https://twitter.com/jorge_cerda_/status/644284954923417605)

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brobinson
Direct link:
[https://video.twimg.com/ext_tw_video/644284669375197184/pu/v...](https://video.twimg.com/ext_tw_video/644284669375197184/pu/vid/1280x720/TnUxYLptB_rlyMb8.mp4)

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lelandbatey
Mirror here:
[http://mirror.xwl.me/2015_chile_earthquake00.mp4](http://mirror.xwl.me/2015_chile_earthquake00.mp4)

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kcole16
Currently in Santiago, building shook for well over a minute. No damage here
though

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privong
I'm in Concepcion, farther south and I felt (mild to moderate) shaking for ~6
minutes, with varying intensity. Also no damage here, and people essentially
continue on with life as usual, aside from the towns near the coast, which
were evacuated because of tsunami danger.

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acdanger
It's now being reported as an 8.3 earthquake, not 7.9/7.3 as reported in the
article.

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MCRed
I spent two years in Chile and so my Facebook friends list is full of
Chileans. One really interesting thing-- that I haven't seen before-- is
Facebook has a feature for them to check in and say they are safe. I can see
at a glance who of my friends has checked in and who hasn't.

Big props to Facebook for this feature!

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kitwalker12
That feature was really helpful during the recent Nepal earthquake as well

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kitwalker12
I'm new to US and ipso facto new to weather alerts on my phone. So the first
time I saw the alert, kinda shit my pants as I had been in Andaman hours
before the 2004 Tsunami

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bankim
Looking at the latitude, can Tsunami go as far as Australia/NZ?

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billforsternz
We have a tsunami warning in NZ, so yes.

