April 2, 2014
The northern coast of Chile has been struck by a Great earthquake this evening, shaking the South America continent for hundreds of miles and thrusting a tsunami onshore and across the Pacific Ocean. Notably, this earthquake occurred in a well known seismic gap, the sole reach of South America’s Pacific coast subduction zone that did not rupture in the 20th (or 21st) century. In that sense, this was one of the most likely places on the planet to have such an earthquake, so it comes as little surprise. Further hinting at the inevitability of this evening’s quake, the epicentral area has been experiencing a series of significant (M6-7) earthquakes all month. Turns out those were foreshocks. There was speculative buzz about that already, but of course before this mainshock we had no way of knowing whether the buzz would be borne out. Now we know.
A magnitude 8.2 earthquake is enormous, and its effects are truly global. As I write this, the planet is still ringing from the jolt, with strong seismic surface waves being picked up on instruments the world over. Meanwhile a massive ocean wave is spreading outward through the Pacific from the vast swath of Chilean shelf that heaved it upwards during the quake. These phenomena are unfolding before our eyes, and before the eyes of the scientists and agencies that help understand and mitigate the catastrophe. Indeed the Pacific Tsunami Warning Center is currently deliberating over whether they will need to issue a tsunami warning to Hawaii in 12 hours, when the waves will strike the island. [update, 16:20 UTC April 2: Hawaii had a 0.8m tsunami starting a little before 14:00 UTC; an advisory will last much of the day because of hazardous currents in the Pacific, but the risk of inundation from this tsunami has pretty much subsided.]
Watching an earthquake unfold
With global transmission of data through the internet, we can watch these phenomena unfold before our eyes. There are plenty of sites that host open, public, or accessible government data that record these events. Below is a selection of my favorites for watching earthquakes and their effects in near real time:
Seismograms of the Global Seismic Network. These are updated every ~30 minutes.
A *live* seismogram display from Berkeley, CA. This was part of an art piece, so it’s a little less technical, but it’s a great site to check out when you know there are teleseismic surface waves racing through the U.S. and you want to see what’s happening beneath your feet that you can’t feel.
Sea level data from globally distributed buoys and tide guages. Very interactive selection and easy data display:
(as I write this, Chile’s show the 2 m tsunami clearly)
And of course, for expert and official interpretation of those sea level measurements, you should definitely turn to your regional Tsunami Warning Center:
http://ptwc.weather.gov/ (links on top and left to other regions)
Of course to find out that you should be checking out these resources, you’ll have to either religiously check the USGS Recent Earthquakes page, OR take advantage of the fancy option: having the USGS alert you specifically when significant events happen. The Earthquake Notification Service lets you be one of the first to know when significant events occur anywhere in the world. You can set your magnitude thresholds based on your commitment.
There are also a lot of earthquake alert Apps–a review of those is for another post.
If you’re willing to brave the overwhelming winds of data, images, and links that may or may not have citations and sources, Twitter is actually a profoundly effective and rapid way to learn about unfolding disasters. I think this is Twitter’s primary contribution to the world, although that’s my disaster-centric bias.
So next time the Earth decides to lurch around violently, you can keep track of all its various seismic motions from the comfort of your living room. Or from outside/high ground/somewhere safe.