<p><a href="http://en.wikipedia.org/wiki/Robert_Mallet">Robert Mallet</a> is sometimes referred to as the "father of seismology." He was helped (around 1850) by the newly created science of photography, which enabled him to create seismic "maps" of the earth, at different depths.</p>

<p>He has started life as an iron engineer/manufacturer, but turned his talents to seismology after a number of devastating earthquakes in Europe. His earlier work with iron gave him a background in the use of explosives to "open up" the earth at critical points.</p>

<p><a href="http://en.wikipedia.org/wiki/Paleoseismology">Paleoseismology</a> is a related field that relies on paleontology to form estimates of various properties of the earth.</p>

CC BY-SA 3.0
2014-04-25T14:59:05.660Z
@BenA.Noone: I said that paleoseismology was an alternative method. You need to use pretty much the same data for this work, but it can be measured or evaluated in different ways.
Tom Au
CC BY-SA 3.0
2014-04-25T15:04:40.010Z
I would say that paleoseismology relies on sedimentology indeed but not specifically on paleontology. Unless you had a specific method in mind?
plannapus
CC BY-SA 3.0
2014-04-25T14:41:29.740Z
2014-04-25T14:41:29.740Z
Tom Au
<p>Since @TomAu answered the bonus points, I'll focus on the question</p>

<blockquote>
  <p>Is this [seismology] the only way of measuring the inner sections of the earth?</p>
</blockquote>

<p>No, it is not. Some interfaces, like the crust-mantle interface (the Moho), can be mapped using <strong>gravity anomalies</strong>. The basic idea is that the gravity anomaly is the difference between the Earths gravity and the gravity of a reference model (usually an ellipsoid). The anomaly is usually due to an over-correction or an under-correction. In places where the crust is thinner, there is more mass than was removed in reference because the mantle is denser than the crust (places marked with a "+"  sign in the figure below). This excess mass creates a positive gravity anomaly. Likewise, if the crust is thicker there will be a mass deficiency (marked by the "-" sign) and we'll see a negative anomaly. So we can infer the topography of the Moho from these anomalies in the gravity field.</p>

<p><img src="https://i.sstatic.net/6Rcvt.png" alt="enter image description here"></p>

<p>However, a radially varying density model (like the <a href="http://en.wikipedia.org/wiki/Preliminary_reference_Earth_model" rel="noreferrer">PREM</a> for seismology) is not possible to estimate from the gravity field alone. That is because there is an infinite number of combinations of this kind of model that yield the same gravity field.  </p>

CC BY-SA 3.0
2014-05-15T20:00:21.573Z
2014-05-15T20:00:21.573Z
Leo Uieda
<p>Answers from these two questions: 
<a href="https://earthscience.stackexchange.com/questions/517/how-can-we-guess-the-size-of-the-earths-inner-coreand-what-its-made-of">How can we guess the size of the earths inner core?</a> <br/>
&amp; 
<a href="https://earthscience.stackexchange.com/questions/555/how-can-we-measure-the-thickness-of-the-earths-mantle">How can we measure the thickness of the earths mantle?</a> 
use seismic waves as the <br/>method for detirmining size and thickness of sections in the earth.<br/></p>

<p>Is this the only way of measuring the inner sections of the earth?</p>

<p><strong>Bonus Points:</strong> Where did the idea of using seismic waves to measure earth's layers start?</p>

CC BY-SA 4.0
2023-09-04T13:02:42.000Z
It probably started with the discovery of sonar.
John
CC BY-SA 3.0
2014-04-25T16:23:18.087Z
Gravity might be away (ie, how do we approximate g ~9.8 at the surface with 4 different layers), if we assume 4 basic temperature/pressure boundaries. But it really is The BEST way.
Neo
CC BY-SA 3.0
2014-05-15T19:31:17.267Z
@Neo, gravity would not do because there are infinite combinations of layers that give the same gravity field outside of the Earth. That is why we can use a reference ellipsoid (the Normal Earth) with the same mass as the Earth without making any assumptions about the density distribution inside the ellipsoid. It is also a pain for those of us working on gravity inverse problems.
Leo Uieda
CC BY-SA 3.0
2014-05-15T19:35:52.013Z
@Neo but you can (and many do) use gravity to map undulations in the layers. But something like PREM would probably not be possible with gravity alone.
Leo Uieda
<measurements><seismology>
Is seismology really the only way to measure the thickness of Earth's layers?
Ben A. Noone
# Is seismology really the only way to measure the thickness of Earth's layers?

(Asked by: username_0 on 2014-04-25)

Answers from these two questions:
[How can we guess the size of the earths inner core?](https://earthscience.stackexchange.com/questions/517/how-can-we-guess-the-size-of-the-earths-inner-coreand-what-its-made-of)   
&
[How can we measure the thickness of the earths mantle?](https://earthscience.stackexchange.com/questions/555/how-can-we-measure-the-thickness-of-the-earths-mantle)
use seismic waves as the   
method for detirmining size and thickness of sections in the earth.

Is this the only way of measuring the inner sections of the earth?

**Bonus Points:** Where did the idea of using seismic waves to measure earth's layers start?

**Tags:** measurements, seismology

> **Comments:**
> **username_2**: Gravity might be away (ie, how do we approximate g ~9.8 at the surface with 4 different layers), if we assume 4 basic temperature/pressure boundaries. But it really is The BEST way.  
> **username_3**: @username_2, gravity would not do because there are infinite combinations of layers that give the same gravity field outside of the Earth. That is why we can use a reference ellipsoid (the Normal Earth) with the same mass as the Earth without making any assumptions about the density distribution inside the ellipsoid. It is also a pain for those of us working on gravity inverse problems.  
> **username_3**: @username_2 but you can (and many do) use gravity to map undulations in the layers. But something like PREM would probably not be possible with gravity alone.  
> **username_1**: It probably started with the discovery of sonar.  

---

## 2 answers

### Answer by username_3 on 2014-05-15. Score: 6 | Accepted answer

Since @username_4 answered the bonus points, I'll focus on the question

> Is this [seismology] the only way of measuring the inner sections of the earth?

No, it is not. Some interfaces, like the crust-mantle interface (the Moho), can be mapped using **gravity anomalies**. The basic idea is that the gravity anomaly is the difference between the Earths gravity and the gravity of a reference model (usually an ellipsoid). The anomaly is usually due to an over-correction or an under-correction. In places where the crust is thinner, there is more mass than was removed in reference because the mantle is denser than the crust (places marked with a "+" sign in the figure below). This excess mass creates a positive gravity anomaly. Likewise, if the crust is thicker there will be a mass deficiency (marked by the "-" sign) and we'll see a negative anomaly. So we can infer the topography of the Moho from these anomalies in the gravity field.

![enter image description here](https://i.sstatic.net/6Rcvt.png)

However, a radially varying density model (like the [PREM](http://en.wikipedia.org/wiki/Preliminary_reference_Earth_model) for seismology) is not possible to estimate from the gravity field alone. That is because there is an infinite number of combinations of this kind of model that yield the same gravity field.


---

### Answer by username_4 on 2014-04-25. Score: 6

[Robert Mallet](http://en.wikipedia.org/wiki/Robert_Mallet) is sometimes referred to as the "father of seismology." He was helped (around 1850) by the newly created science of photography, which enabled him to create seismic "maps" of the earth, at different depths.

He has started life as an iron engineer/manufacturer, but turned his talents to seismology after a number of devastating earthquakes in Europe. His earlier work with iron gave him a background in the use of explosives to "open up" the earth at critical points.

[Paleoseismology](http://en.wikipedia.org/wiki/Paleoseismology) is a related field that relies on paleontology to form estimates of various properties of the earth.

> **Comments:**
> **username_4**: @username_0: I said that paleoseismology was an alternative method. You need to use pretty much the same data for this work, but it can be measured or evaluated in different ways.  
> **username_5**: I would say that paleoseismology relies on sedimentology indeed but not specifically on paleontology. Unless you had a specific method in mind?  

---

