<p>Gravity can be used to investigate the lower crust and upper mantle (see for example <a href="http://dx.doi.org/10.1016%2Fj.jag.2014.02.003" rel="nofollow noreferrer">Fullea et al, 2014</a>). Satellite measurements of gravity could even be used to investigate deeper structures in the mantle, like subducting slabs (<a href="http://dx.doi.org/10.1038%2Fngeo2063" rel="nofollow noreferrer">Panet, 2014</a>). However, I couldn't find any use of gravity data to probe deeper, into the core for example.</p>
<p>The <a href="http://en.wikipedia.org/wiki/Magnetotellurics" rel="nofollow noreferrer">magnetotelluric method</a> is sometimes used for deep crustal structure. And features of the geomagnetic field, like <a href="http://en.wikipedia.org/wiki/Geomagnetic_secular_variation" rel="nofollow noreferrer">secular variation</a>, can be inverted to investigate as far down as the outer core (<a href="http://dx.doi.org/10.1016/S0031-9201(96)03187-1" rel="nofollow noreferrer">Gubbins, 1996</a>).</p>
<p>However, the most common and well developed method to image the lower mantle and core is still through seismic waves.</p>

CC BY-SA 4.0
2014-05-15T18:44:26.843Z
2021-10-13T07:25:24.407Z
2021-10-13T07:25:24.407Z
Leo Uieda
<p>One interesting and relatively new technique is by the detection of <a href="http://en.wikipedia.org/wiki/Geoneutrino">geoneutrinos</a>. These particles are produced by radioactive decay in the Earth's interior. They are uncommonly suitable for probing the deep Earth because -- unlike most particles and waves -- they can travel through thousands of kilometres of rock with very little absorption. Of course, this very same characteristic makes actually <em>detecting</em> them something of a challenge, and detectors tend to be <a href="http://www.e15.ph.tum.de/research_and_projects/lena/">rather large</a> (in the thousands of cubic metres). <a href="http://www.nature.com/nature/journal/v436/n7050/abs/nature03980.html">Araki et al. (2005)</a> gives some early results -- but as the Wikipedia article shows, there are more and bigger detectors on the drawing boards, so we should expect to see more geoneutrino results in the coming years and decades. <a href="http://scicolloq.gsfc.nasa.gov/McDonough.html">This abstract</a> gives the best elevator pitch I've found so far for geoneutrino research:</p>

<blockquote>
  <p>Radioactive decay of U and Th gives off ghost-like, neutrino particles that can be detected by 1000 ton detectors built a mile underground, where they are shielded from the cosmic rays that rain down on the Earth. Collaborations between physicists and geologists are detecting these "geo-neutrinos". Future underwater detectors, deployed at different points on the ocean floor, will create a neutrino tomographic image of mantle structures sited at the base of the mantle above the core.</p>
</blockquote>

CC BY-SA 3.0
2014-05-26T00:12:35.570Z
But due to the catastrophically low cross sections of neutrinos with normal matter and therefore our detectors, I don't think we will be able to actually _resolve_ something coming from the interior in depth. Counter-thoughts?
AtmosphericPrisonEscape
CC BY-SA 3.0
2014-05-20T10:43:46.243Z
2014-05-20T10:43:46.243Z
Pont
<p>Inverse problems are some of the most important mathematical problems in science and mathematics. Inverse problems arise in many branches of geophysics, medical imaging, remote sensing, ocean acoustic tomography, nondestructive testing, astronomy, physics and many other fields.</p>

<p>Geophysicists remotely measure the seismic (acoustic), gravity, and electromagnetic fields of the earth and then treat the inverse problem to constrain the properties of the earth's interior.</p>

CC BY-SA 3.0
2014-05-21T02:17:45.827Z
2014-05-21T02:17:45.827Z
Mark Rovetta
<p>It is well-known that we can learn a lot about the structure of the lower crust, mantle, and core by observing the ways in which they refract different kinds of seismic waves. </p>

<p>Do we have any <em>other</em> ways of imaging the deeper parts of the Earth, though? </p>

CC BY-SA 3.0
2014-05-14T00:39:15.713Z
http://earthscience.stackexchange.com/questions/517/how-can-we-guess-the-size-of-the-earths-inner-coreand-what-its-made-of is somewhat relevent, even though most of the answers are seismology based there is some information that is important to the question
Neo
CC BY-SA 3.0
2014-05-15T19:06:44.713Z
I can't tell if eclogite would fall within the scope of structure or not.
Siv
<geophysics><seismology>
Are there any techniques for imaging the deep Earth besides seismic waves?
senshin
# Are there any techniques for imaging the deep Earth besides seismic waves?

(Asked by: username_0 on 2014-05-13)

It is well-known that we can learn a lot about the structure of the lower crust, mantle, and core by observing the ways in which they refract different kinds of seismic waves.

Do we have any *other* ways of imaging the deeper parts of the Earth, though?

**Tags:** geophysics, seismology

> **Comments:**
> **username_1**: http://earthscience.stackexchange.com/questions/517/how-can-we-guess-the-size-of-the-earths-inner-coreand-what-its-made-of is somewhat relevent, even though most of the answers are seismology based there is some information that is important to the question  
> **username_2**: I can't tell if eclogite would fall within the scope of structure or not.  

---

## 3 answers

### Answer by username_3 on 2014-05-15. Score: 14

Gravity can be used to investigate the lower crust and upper mantle (see for example [Fullea et al, 2014](http://dx.doi.org/10.1016%2Fj.jag.2014.02.003)). Satellite measurements of gravity could even be used to investigate deeper structures in the mantle, like subducting slabs ([Panet, 2014](http://dx.doi.org/10.1038%2Fngeo2063)). However, I couldn't find any use of gravity data to probe deeper, into the core for example.

The [magnetotelluric method](http://en.wikipedia.org/wiki/Magnetotellurics) is sometimes used for deep crustal structure. And features of the geomagnetic field, like [secular variation](http://en.wikipedia.org/wiki/Geomagnetic_secular_variation), can be inverted to investigate as far down as the outer core ([Gubbins, 1996](http://dx.doi.org/10.1016/S0031-9201(96)03187-1)).

However, the most common and well developed method to image the lower mantle and core is still through seismic waves.


---

### Answer by username_4 on 2014-05-20. Score: 10

One interesting and relatively new technique is by the detection of [geoneutrinos](http://en.wikipedia.org/wiki/Geoneutrino). These particles are produced by radioactive decay in the Earth's interior. They are uncommonly suitable for probing the deep Earth because -- unlike most particles and waves -- they can travel through thousands of kilometres of rock with very little absorption. Of course, this very same characteristic makes actually *detecting* them something of a challenge, and detectors tend to be [rather large](http://www.e15.ph.tum.de/research_and_projects/lena/) (in the thousands of cubic metres). [Araki et al. (2005)](http://www.nature.com/nature/journal/v436/n7050/abs/nature03980.html) gives some early results -- but as the Wikipedia article shows, there are more and bigger detectors on the drawing boards, so we should expect to see more geoneutrino results in the coming years and decades. [This abstract](http://scicolloq.gsfc.nasa.gov/McDonough.html) gives the best elevator pitch I've found so far for geoneutrino research:

> Radioactive decay of U and Th gives off ghost-like, neutrino particles that can be detected by 1000 ton detectors built a mile underground, where they are shielded from the cosmic rays that rain down on the Earth. Collaborations between physicists and geologists are detecting these "geo-neutrinos". Future underwater detectors, deployed at different points on the ocean floor, will create a neutrino tomographic image of mantle structures sited at the base of the mantle above the core.

> **Comments:**
> **username_5**: But due to the catastrophically low cross sections of neutrinos with normal matter and therefore our detectors, I don't think we will be able to actually _resolve_ something coming from the interior in depth. Counter-thoughts?  

---

### Answer by username_6 on 2014-05-21. Score: 2

Inverse problems are some of the most important mathematical problems in science and mathematics. Inverse problems arise in many branches of geophysics, medical imaging, remote sensing, ocean acoustic tomography, nondestructive testing, astronomy, physics and many other fields.

Geophysicists remotely measure the seismic (acoustic), gravity, and electromagnetic fields of the earth and then treat the inverse problem to constrain the properties of the earth's interior.


---

