June 22, 2012

40 years of earthquakes on one seismogram

Posted by Austin Elliott

Want to see the pulse of the Earth?

Last year marked the 50th anniversary of the Albuquerque Seismological Laboratory (ASL), a facility in the quiet mountains of New Mexico that is " href="http://pubs.usgs.gov/fs/2011/3065/pdf/FS11-3065.pdf" onclick="javascript:_gaq.push(['_trackEvent','download','http://pubs.usgs.gov/fs/2011/3065/pdf/FS11-3065.pdf']);" target="_blank">used by the USGS as a hub to maintain both the instruments and data transmission capabilities of the global (GNS) and national (ANSS) seismic networks. The ASL is used to develop new seismograph technology and to test and calibrate instruments in the absence of urban noise and in close proximity to several long-running reference stations.

In honor of the golden anniversary in June 2011 the Incorporated Research Institutions for Seismology put together the [nearly] continuous record of seismograms from these long-running stations in a plot that’s simple, beautiful, and fascinating. I’m going to hang this poster somewhere.

40 years of global earthquakes as recorded at a site outside of Albuquerque, New Mexico. Check out IRIS’s website for the full size version and info about how it was created.

You can read " href="http://www.iris.edu/hq/files/iris_news/docs/40Year_Poster_Tech_Summary.pdf" onclick="javascript:_gaq.push(['_trackEvent','download','http://www.iris.edu/hq/files/iris_news/docs/40Year_Poster_Tech_Summary.pdf']);" target="_blank">how the plot was generated and details of the " href="http://www.iris.edu/hq/files/iris_news/docs/40Year_Poster_Earthquake_List.pdf" onclick="javascript:_gaq.push(['_trackEvent','download','http://www.iris.edu/hq/files/iris_news/docs/40Year_Poster_Earthquake_List.pdf']);" target="_blank">more prominent earthquakes at IRIS’s website, but there are some striking things the keen observer will find right off the bat, at least after a brief orientation:

Each of the 465 lines represents a single month of seismic record, squished to fit on the page. The numbers at the bottom represent days of the month, and for months with fewer than 31 days the tail ends of the lines (the final 1-3 days) are filled with zeroes, making them flat lines. Read it from top to bottom and left to right like a book, and you’ll see a rich mixture of small local or regional earthquakes sprinkled among large, long-duration teleseismic earthquakes–ones of substantial magnitude that occurred far around the Earth but were recorded at these stations in Albuquerque thanks to the immense energy they released.

The two largest events are conspicuous in the final years. These of course are the M9.1 Sunda megathrust earthquake that hit Sumatra, Indonesia in 2004, and the M9.0 Tohoku earthquake that hit Japan last year. The bottom right corner is full of other megaquakes, mostly centered in Indonesia, save for the M8.8 Maule, Chile earthquake of 2010.

Pick your most significant historical earthquake from the last 4 decades and try to find it on this plot! Or just marvel at this continuous record of our rocky planet’s pulse.