# Rock analogs for structural geology

This is a compilation of the properties of different analog materials used to simulate deformational processes in structural geology. Such experiments are often called analog or analogue models. The organization of this page follows the review of rock analog materials in structural geology and tectonics of Reber et al. 2020.

## Materials used to simulate upper crustal deformation

These materials need to exhibit brittle deformation upon failure as well as elastic and viscous deformation before failure.

### Materials that simulate upper crustal deformation

| Material | Applications | Studies |
| Plexiglas and glass | Plexiglas and glass is useful for many applications. Some of which are: stress analysis of grains fracturing earthquake dynamics | Erdogan & Sih 1963; Thomas and Pollard 1993; Cooke & Pollard,1996; Daniels & Hayman, 2008; Lu, Lapusta & Rosakis, 2007; Owens & Daniels, 2011; Rubino, Rosakis, & Lapusta, 2019 |
| Gelatin | Gelatin has been used to simulate: tensile fracturing thrust faults dyke and sill emplacement | Bot, vanAmerongon, Groot, Hoekstra, & Agterof, 1996; Brizzi, Funiciello, Corbi, Di Giuseppe, & Mojoli, 2016; Canon-Tapia and Merle, 2006; Corbi et al., 2011; Corbi et al., 2013; Di Giuseppe et al., 2009; Hyndman & Alt, 1987; Kavanagh, Menand, & Daniels, 2013; Kavanagh, Menand, & Sparks, 2006; Kervyn, Ernst, de Vires, Mathieu, & Jacobs, 2009; Kobchenko et al., 2014; Lee, Reber, Hayman, & Wheeler, 2016; Menand & Tait, 2002; Pollard, 1973; Rivalta, Bottinger, & Dahm, 2005; Touvet, Balmforth, Craster, & Sutherland, 2011; van Otterloo & Cruden, 2016 |
| Foam | Foam is mostly used as an analog simulating elastic loading on the crust between earthquake events. If the foam used has a low stiffness, it can be dynamically scaled to preexisting fault surfaces' and earthquake cycles | Anooshehpoor & Brune, 1999; Anooshehpoor, Heaton, Shi & Brune, 1999; Brune,1973; Caniven et al., 2015; Rosenau et al., 2017; Rosenau, Lohrmann, & Oncken, 2009; Rosenau & Oncken, 2009 |
| Clays | Clay is used to simulate deformation in the upper crust through distributed deformation and localized failure. The properties of clay depend on the mineralogy, grain size distribution and water content. | Bonanno, et al., 2017; Bonini et al., 2016; Cooke and van der Elst, 2012; DeGroot & Lunne, 2007; Eisenstadt & Sims, 2005; Hatem, Cooke, & Toeneboehn, 2017; Henza, Withjack, & Schlische, 2010; Kenny, 1967; Mitra & Paul, 2011; Paul & Mitra, 2013; Toeneboehn, 2017; Toeneboehn, 2018; White, 1949; Withjack, Henza, & Schlische, 2017 |

### Dry granular materials

| Material | Material | Applications | Studies |
| Sand | Sand | During deformation, sand exhibits distributed deformation, compaction followed by dilatation, prior to failure via grain rearrangement. Sand is often used to simulate folding or faulting. | Abdelmalak et al., 2016; Cobbold, Durand, & Mourgues, 2001; Daniels & Hayman, 2008; Davis, Suppe, & Dahlen,1983; Galland, Burchardt, Hallot, Mourgues, & Bulois, 2014; Galland, Cobbold, Hallot, d'Ars, & Delavaud, 2006; Gomes, 2013; Hayman, Ducloue, Foco, & Daniels, 2011; Herbert et al., 2015; Klinkmuller et al., 2016; Lohrmann et al, 2003; Panien, Buiter, Schreurs, & Pfiffner, 2006; Rosenau et al., 2009 |
| Micro beads | Micro beads | Micro beads are useful for: Situations where low friction and mechanical layering are desired in crustal and lithospheric models Salt tectonic modeling because of adjustable density | Boutelier, Schrank, & Cruden, 2008; Dooley, Jackson, & Hudec, 2007; Dooley, Jackson, & Hudec, 2009; Duffy et al., 2018; Hudec, Jackson, & Schttltz-Ela, 2009; Jackson et al., 2019 Rossi & Storti, 2003; Schellart, 2000 |
| Other | Lentils | Lentils have been used to study the distribution of shear surfaces observed in clay rich sediments. | Tarling & Rowe, 2016 |
| Other | Crushed Walnut Shells | Crushed walnut shells have been used for their low density and non-abrasive nature. | Cruz, Teyssier, Perg, Take, & Fayon, 2008 |
| Other | Poppy Seeds | Poppy seeds were used in an analog model as particles in suspension for determining the yield strength of subliquidus basalt. | Hoover, Cashman, & Manga, 2001 |
| Other | Rice | Rice has been used to simulate earthquakes and fault roughness. | Rosenau et al., 2009 |
| Other | Sugar | Sugar has been used: In subduction earthquake cycle models As an analog for the brittle upper crust | Moore, Vendeville, & Wiltschko, 2005; Rosenau et al., 2009; Schellart, 2000; Schellart & Strak, 2016 |
| Other | Sand-hemihydrate calcium sulphate | Sand-hemihydrate calcium sulphate mixtures, in different mixing ratios, are used as an "ultra-weak" sandstone to simulate fault and fracture processes in analogue modelling at the outcrop scale (about 10 m). | Massaro et al., 2022; Massaro et al., 2023 |

## Materials used to simulate deformation of the lower crust and mantle

Various fluids are used to simulate deformation of the lower crust and mantle, such as: linear, non-linear, and yield stress fluids.
| Fluid type | Material | Application | Studies |
| Linear viscous fluids | Silicone Oils/Polymers | Silicone oils/polymers can have varying viscosities, which can be changed by adding fillers (dry granular materials) or aolic acid. In combination with brittle model materials, silicone oils/polymers can investigate many processes in salt tectonics, including the deformation of sediments adjacent and above a salt body. | Boutelier, Schrank, & Cruden, 2008; ten Grotenhuis et al., 2002; Weijermars, 1986; Brun & Fort, 2004; Brun & Mauduit, 2009; Cobbold, Szatmari, Demercian, Coelho, & Rossello, 1995; Dooley & Hudec, 2017; Dooley et al., 2009; Dooley, Jackson & Hudec, 2013; Dooley, Jackson & Hudec, 2015; Duffy et al., 2018; Letouzey, Colletta, Vially & Chermette, 1995; Smit, Brun, Fort, Cloetingh, & Ben-Avraham, 2008; Vendeville & Jackson, 1992; Weijermars, 1986; Weijermars, Jackson, & Vendeville, 1993 |
| Linear viscous fluids | Honey* | Honey, glucose syrup, and molasses exhibit strain independent deformation. The viscosity depends on the sugar content and temperature of the material. This makes them suitable to simulate the lower crust and mantle. *Honey can also be used as a non-linear viscous fluid under certain conditions. | Schellart, 2011 |
| Linear viscous fluids | Glucose Syrup | Honey, glucose syrup, and molasses exhibit strain independent deformation. The viscosity depends on the sugar content and temperature of the material. This makes them suitable to simulate the lower crust and mantle. *Honey can also be used as a non-linear viscous fluid under certain conditions. | Schellart, 2011 |
| Linear viscous fluids | Molasses | Honey, glucose syrup, and molasses exhibit strain independent deformation. The viscosity depends on the sugar content and temperature of the material. This makes them suitable to simulate the lower crust and mantle. *Honey can also be used as a non-linear viscous fluid under certain conditions. | Schellart, 2011 |
| Linear viscous fluids | Gum Rosin | Gum rosin was used to study thermomechanical processes in the lithospheric mantle. | Cobbold & Jackson, 1992 |
| Linear viscous fluids | Water | Water has been used to model any low viscosity material. | Paola et al., 2006 |
| Non-linear viscous fluids | Silicone Oils/Polymers | Silicone is also used as a non-linear viscous material by adding high amounts of filler. The most common filler material used is plasticine. | Boutelier et al., 2008; Rudolf, Boutelier, Rosenau, Schreurs, & Oncken, 2016 |
| Bingham fluid | Paraffin Wax | Paraffin wax can be used in analog experiments as a linear or non-linear yield stress fluid. By mixing paraffin wax with petrolatum, the yield stress, shear thinning, and shear softening behavior can be modified. | Duarte et al., 2014; Rossetti et al., 1999 |
| Bingham fluid | Petrolatum | Petrolatum is commonly used as: A filler with paraffin wax A lubricant At this time, pure petrolatum has not been used for analog material. | Cobbold, 1975; Duarte et al., 2014; Neurath and Smith, 1892 |
| Hershel-Bulkley fluid | Carbopol | Carbopol has been used in analogue models of: Gravity driven flow Rayleigh-Benard-like convection Localized shear zones Thermal intrusions Semi-brittle processes | Balmforth & Rust, 2009; Birren & Reber, 2019; Davaille et al., 2013; Di Federico et al., 2017; Reber et al., 2015; Schrank, Boutelier, & Cruden, 2008 |

## Materials used to simulate deformation of the middle crust
### Composite Model Materials

Composite materials combine phases with different physical properties. A common composite mixture contains dry granular materials and fluids. These analog materials have been used:
* Sediment transport (Parker et al., 1982) using low viscosity fluids
* Dynamics in the middle crust (Mookerjee et al., 2017; Reber et al., 2014) employing high viscosity fluids
* Stick-slip dynamics (Higashi and Sumita, 2009; Reber et al., 2014)
* Strain softening and hardening processes (Panien et al., 2006)
The most commonly used granular materials in composite mixtures are:
* Sand
* Glass beads
* Acrylic discs
Common fluids used in composite mixtures are:
* Carbopol
* Silicone
* Wax, which can behave as a brittle or viscous material depending on the melting temperature (Mookerjee et al., 2017)

### Visco-elasto-plastic model materials

Visco-elasto-plastic deformation exhibits a combination of elastic, viscous, and plastic deformation at the same time. Various asphalts and bituminous materials demonstrate visco-elasto-plastic deformation but they are rarely as modeling materials (McBirney and Best, 1961).Common modeling materials demonstrating complex rheology are;
* Carbopol (Piau, 2007; Shafiei et al., 2018)
* Kaolinite clay (Cooke and van der Elst, 2012)