An Amazing 40-Year-Long Seismogram: A Whole New Way of Seeing Our Planet Quake

Alan Kafka
Weston Observatory
Department of Earth and Environmental Sciences
Boston College

This seismogram, produced by the Albuquerque Seismological Laboratory (one of the all-time best seismic stations on Earth), shows a 40-year record of seismic recording!

(Higher-quality versions of this seismogram can be found here and here.)

This is a view of the Earth quaking that has never been seen before. It’s that mind-boggling!

Also shown below for comparison is a more typical 24-hour seismogram, with each line representing an hour. In the 40-year seismogram, instead of each line representing an hour, each line represents a month. The vertical axis shows the year, the horizontal axis shows the day of the month, and the labels on the right side of the vertical axis identify significant, globally recorded earthquakes.

Three relatively small earthquakes can be seen in the 24-hour seismogram (recorded in Massachusetts at Weston Observatory on August 23, 2011):

Virginia, Magnitude 5.8
Colorado, Magnitude 5.3
Colorado, Magnitude 4.6

Three mega-quakes, the largest earthquakes recorded since 1972, can be seen on the 40-year seismogram:

Sumatra 2004, Magnitude 9.1
Japan 2011, Magnitude 9.0
Chile 2010, Magnitude 8.8

Also seen on the 40-year seismogram are the many smaller earthquakes that happen every month. The smallest earthquakes that can be seen on this seismogram are about magnitude 6 (i.e., about as big as the Virginia earthquake shown on the 24-hour seismogram).

Note: The title of this blog has been updated from “BC-ESP Discussion Forum” to “Musings in the Quake Zoneto reflect what it has evolved into.

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