# Geomathematics

**Geomathematics** or **Mathematical Geophysics** is the application of mathematical intuition to solve problems in Geophysics. The most complicated problem in Geophysics is
the solution of the three dimensional inverse problem, where
observational constraints are used to infer physical properties.
The inverse procedure is much more sophisticated than the normal direct computation of what should be observed from a physical system.
The estimation procedure is often dubbed the inversion strategy (also called the inverse problem) as the procedure is intended to estimate from a set of observations the circumstances that produced them. The Inverse Process is thus the converse of the classical scientific method.

## Applications

### Terrestrial Tomography

An important research area that utilises inverse methods is seismic tomography, a technique for imaging the subsurface of the Earth using seismic waves. Traditionally seismic waves produced by earthquakes or anthropogenic seismic sources (e.g., explosives, marine air guns) were used.

### Crystallography

Crystallography is one of the traditional areas of geology that use mathematics. Crystallographers make use of linear algebra by using the Metrical Matrix. The Metrical Matrix uses the basis vectors of the unit cell dimensions to find the volume of a unit cell, d-spacings, the angle between two planes, the angle between atoms, and the bond length.[1] Miller's Index is also helpful in the application of the Metrical Matrix. Brag's equation is also useful when using an electron microscope to be able to show relationship between light diffraction angles, wavelength, and the d-spacings within a sample.[1]

### Geophysics

Geophysics is one of the most math heavy disciplines of Earth Science. There are many applications which include gravity, magnetic, seismic, electric, electromagnetic, resistivity, radioactivity, induced polarization, and well logging.[2] Gravity and magnetic methods share similar characteristics because they're measuring small changes in the gravitational field based on the density of the rocks in that area.[2] While similar gravity fields tend to be more uniform and smooth compared to magnetic fields. Gravity is used often for oil exploration and seismic can also be used, but it is often significantly more expensive.[2] Seismic is used more than most geophysics techniques because of its ability to penetrate, its resolution, and its accuracy.

### Geomorphology

Many applications of mathematics in geomorphology are related to water. In the soil aspect things like Darcy's law, Stoke's law, and porosity are used.

- Darcy's law is used when one has a saturated soil that is uniform to describe how fluid flows through that medium.[3] This type of work would fall under hydrogeology.
- Stoke's law measures how quickly different sized particles will settle out of a fluid.[3] This is used when doing pipette analysis of soils to find the percentage sand vs silt vs clay.[4] A potential error is it assumes perfectly spherical particles which don't exist.
- Stream power is used to find the ability of a river to incise into the river bed. This is applicable to see where a river is likely to fail and change course or when looking at the damage of losing stream sediments on a river system (like downstream of a dam).
- Differential equations can be used in multiple areas of geomorphology including: The exponential growth equation, distribution of sedimentary rocks, diffusion of gas through rocks, and crenulation cleavages.[5]

### Glaciology

Mathematics in Glaciology consists of theoretical, experimental, and modeling. It usually covers glaciers, sea ice, waterflow, and the land under the glacier.

Polycrystalline ice deforms slower than single crystalline ice, due to the stress being on the basal planes that are already blocked by other ice crystals.[6] It can be mathematically modeled with Hooke's Law to show the elastic characteristics while using Lamé constants.[6] Generally the ice has its linear elasticity constants averaged over one dimension of space to simplify the equations while still maintaining accuracy.[6]

Viscoelastic polycrystalline ice is considered to have low amounts of stress usually below one bar.[6] This type of ice system is where one would test for creep or vibrations from the tension on the ice. One of the more important equations to this area of study is called the relaxation function.[6] Where it's a stress-strain relationship independent of time.[6] This area is usually applied to transportation or building onto floating ice.[6]

Shallow-Ice approximation is useful for glaciers that have variable thickness, with a small amount of stress and variable velocity.[6] One of the main goals of the mathematical work is to be able to predict the stress and velocity. Which can be affected by changes in the properties of the ice and temperature. This is an area in which the basal shear-stress formula can be used.[6]

## References

- Gibbs, G. V.
*The Metrical Matrix in Teaching Mineralogy*. Virginia Polytechnic Institute and State University. pp. 201–212. - Telford, W. M.; Geldart, L. P.; Sheriff, R. E. (1990-10-26).
*Applied Geophysics*(2 ed.). Cambridge University Press. ISBN 9780521339384. - Hillel, Daniel (2003-11-05).
*Introduction to Environmental Soil Physics*(1 ed.). Academic Press. ISBN 9780123486554. - Liu, Cheng; Ph.D, Jack Evett (2008-04-16).
*Soil Properties: Testing, Measurement, and Evaluation*(6 ed.). Pearson. ISBN 9780136141235. - Ferguson, John (2013-12-31).
*Mathematics in Geology*(Softcover reprint of the original 1st ed. 1988 ed.). Springer. ISBN 9789401540117. - Hutter, K. (1983-08-31).
*Theoretical Glaciology: Material Science of Ice and the Mechanics of Glaciers and Ice Sheets*(Softcover reprint of the original 1st ed. 1983 ed.). Springer. ISBN 9789401511698.

- Development, significance, and influence of geomathematics: Observations of one geologist, Daniel F. Merriam,
*Mathematical Geology*, Volume 14, Number 1 / February, 1982 - Handbook of Geomathematics, Freeden, Willi; Nashed, M. Zuhair; Sonar, Thomas (Eds.), ISBN 978-3-642-01547-2, Due: October 2010
- Progress in Geomathematics, Editors Graeme Bonham-Carter, Qiuming Cheng, Springer, 2008, ISBN 978-3-540-69495-3