Monthly spectrograms 2016 - , microseismicity

Spectrograms for 2014 through 2016

Spectrograms for 2012 through 2013

Spectrograms for July 2009 through Dec 2011


A power spectrum is estimated for every hour from 1-second sampled superconducting gravity data. But first, a mean spectral background has been estimated from a succession of five days (can be/shall be improved), and the power of a particular time slice is divided by this average power. The resulting "power above mean" in dB units is indicated by colours.
   The measure of the mean here is the harmonic mean (RMS of decibel units), which emphasizes the lower values. 
   The many singular vertical stripes are caused by earthquakes. The longer-duration blobs and blotches are caused by oceanic waves, often surprisingly far away (see the live gravity monitor, MEM power spectrum); note the skidding of peak power with respect to frequency. 

2015-Dec
2016-Dec 2017-Dec
2016-Jan 2017-Jan
2018-Jan
2016-Feb 2017-Feb

2016-Mar 2017-Mar

2016-Apr 2017-Apr

2016-May 2017-May


2016-Jun 2017-Jun

2016-Jul 2017-Jul

2016-Aug 2017-Aug

2016-Sep 2017-Sep

2016-Oct 2017-Oct

2016-Nov 2017-Nov

2016-Dec 2017-Dec