Tsunami alert as Chile hit by powerful earthquake | Hacker News Reader

Tsunami alert as Chile hit by powerful earthquake

bbc.co.uk

145 pointshanoz31 comments

As always, TheEarthquakeGuy provides clear and up-to-date information on Reddit: https://www.reddit.com/r/worldnews/comments/3l8fse/79magnitu...

Their live thread is here: https://www.reddit.com/live/vlfanix4u5u8

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

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!)

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.

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?

According to Google Maps, I'm approx 2500 kilometers (1600 miles) from the epicenter.

Buenos Aires here, 5th floor. Also felt dizzy for a few minutes.

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.

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.

USGS Event page here: http://earthquake.usgs.gov/earthquakes/eventpage/us20003k7a#...

Edit: Magnitude 6.4 aftershock event page here: http://earthquake.usgs.gov/earthquakes/eventpage/us20003k7w#...

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/

(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?

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

Same here...

The consolidation and eventual application of data generated by government agencies like the USGS should be at least someone's goal, maybe the US Digital Service. Although probably not as big an issue in the continental United States as elsewhere, a 21st-century augmentation to traditional warnings of earthquakes/floods/tornadoes should be a thing if it isn't already.

I also highly recommend the Global Disaster and Alert Communication System set up by the UN and European Commission. Their ranking of orange vs red level events tends to map pretty well to how serious the event is in terms of destruction.

http://www.gdacs.org/

A video from ~600KMs south of the epicenter. https://twitter.com/jorge_cerda_/status/644284954923417605

Direct link: https://video.twimg.com/ext_tw_video/644284669375197184/pu/v...

Mirror here: http://mirror.xwl.me/2015_chile_earthquake00.mp4

Another from CNN Chile https://twitter.com/grasswire/status/644292083423928320

Mirror here: http://mirror.xwl.me/2015_chile_earthquake01.mp4

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

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.

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

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!

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

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

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

We have a tsunami warning in NZ, so yes.

Sure. It takes about 12-15hrs for a Chilean tsunami to reach NZ. There have been a few significant ones in the past eg in 1868, 1877, and 1960.

Most of the time though they don't usually have much effect after travelling that far. Might get some harbour surges and currents etc.

It would almost certainly die in severity before it reaches there. The 2005 Boxing Day earthquake/tsunami happened in Indonesia, and it did reach some parts of Africa but it wasn't a major deal. This tsunami looks weaker in comparison.

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