<p>Interferometric synthetic aperture radar (or <a href="http://en.wikipedia.org/wiki/Interferometric_synthetic_aperture_radar">InSAR)</a> is a remote sensing (airplane or, more commonly, satellite) radar techinque used to measure surface deformation. Repeated measurements of radar amplitudes over a common area are used to estimate changes to surface topography. <a href="http://gji.oxfordjournals.org/content/179/1/549.full.pdf">InSAR measurements of surface changes have been used with numerical models of dyke propagation to model magma chambers in the East African Rift System</a>. </p>

<p>Other geophysical methods that can be used to image/model active magma chambers include seismic interferometry, magnetic and gravity methods. <a href="http://www.eri.u-tokyo.ac.jp/yaoki/2012EPSL.pdf">Here</a> is a recently published example from Japan which used seismic interferometry to image an active magma chamber. Magnetic and gravity measurements can be taken from airplanes, which may be a bit safer than being on the ground. If  the magma chamber has magnetic/density properties different from the surrounding country rock, then mag/grav forward/inverse modelling could be used to create a model of the magma chamber geometry. </p>

CC BY-SA 3.0
2014-09-01T05:50:46.810Z
You're most welcome. I just realised now that you're probably more interested in the seismic example, seeing as you were talking about high frequency tremors. I also had a thought that perhaps measurements of high frequency tremors could be used to characterise mechanical properties of magma chamber/country rock, in a manner similar to what is currently being used in the oil and gas industry to characterise fractures, etc in shale/coal seam oil/gas production.
stevej
CC BY-SA 3.0
2014-09-01T05:54:41.013Z
I will look into that, too.  Perhaps another question is in order!
jonsca
CC BY-SA 3.0
2014-09-01T02:09:58.757Z
2014-09-01T02:50:18.090Z
2014-09-01T02:50:18.090Z
stevej
<p>In a previous question <a href="https://earthscience.stackexchange.com/questions/2400/what-happens-to-the-higher-frequency-content-of-the-tremors-associated-with-a-vo">What happens to the higher frequency content of the tremors associated with a volcanic eruption?</a>, I asked about the high(er) frequency content of a volcanic eruption.</p>

<p>In the same vein, I'm interested to know more about the influence of the geometry of the magma column on this particular frequency content and the methodologies that researchers use to take measurements of circular vents.  Assuming a uniform cylinder all the way to the magma chamber would aid in the mechanical modeling, but I'm sure this betrays quite a bit of the changes in diameter that take place along the way.</p>

<p>Are precise measurements of the vents/magma conduits of volcanoes currently possible, or is this too big of a risk to personnel and equipment?  Which particular techniques (e.g., radar/sonar) would work without having to actually enter the chamber?</p>

<geophysics><measurements><volcanology>
Are there measurement techniques that can help determine the exact geometry of a volcanic vent?
jonsca
# Are there measurement techniques that can help determine the exact geometry of a volcanic vent?

(Asked by: username_0 on 2014-08-31)

In a previous question [What happens to the higher frequency content of the tremors associated with a volcanic eruption?](https://earthscience.stackexchange.com/questions/2400/what-happens-to-the-higher-frequency-content-of-the-tremors-associated-with-a-vo), I asked about the high(er) frequency content of a volcanic eruption.

In the same vein, I'm interested to know more about the influence of the geometry of the magma column on this particular frequency content and the methodologies that researchers use to take measurements of circular vents. Assuming a uniform cylinder all the way to the magma chamber would aid in the mechanical modeling, but I'm sure this betrays quite a bit of the changes in diameter that take place along the way.

Are precise measurements of the vents/magma conduits of volcanoes currently possible, or is this too big of a risk to personnel and equipment? Which particular techniques (e.g., radar/sonar) would work without having to actually enter the chamber?

**Tags:** geophysics, measurements, volcanology


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## 1 answers

### Answer by username_1 on 2014-09-01. Score: 7 | Accepted answer

Interferometric synthetic aperture radar (or [InSAR)](http://en.wikipedia.org/wiki/Interferometric_synthetic_aperture_radar) is a remote sensing (airplane or, more commonly, satellite) radar techinque used to measure surface deformation. Repeated measurements of radar amplitudes over a common area are used to estimate changes to surface topography. [InSAR measurements of surface changes have been used with numerical models of dyke propagation to model magma chambers in the East African Rift System](http://gji.oxfordjournals.org/content/179/1/549.full.pdf).

Other geophysical methods that can be used to image/model active magma chambers include seismic interferometry, magnetic and gravity methods. [Here](http://www.eri.u-tokyo.ac.jp/yaoki/2012EPSL.pdf) is a recently published example from Japan which used seismic interferometry to image an active magma chamber. Magnetic and gravity measurements can be taken from airplanes, which may be a bit safer than being on the ground. If the magma chamber has magnetic/density properties different from the surrounding country rock, then mag/grav forward/inverse modelling could be used to create a model of the magma chamber geometry.

> **Comments:**
> **username_1**: You're most welcome. I just realised now that you're probably more interested in the seismic example, seeing as you were talking about high frequency tremors. I also had a thought that perhaps measurements of high frequency tremors could be used to characterise mechanical properties of magma chamber/country rock, in a manner similar to what is currently being used in the oil and gas industry to characterise fractures, etc in shale/coal seam oil/gas production.  
> **username_0**: I will look into that, too.  Perhaps another question is in order!  

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