Hi all – this is a little webpage about my upcoming visit to Imperial in Feb 2018. If you have any questions in advance feel free to message me!
Why am I visiting?
While I’m at Imperial, I’ll be giving a talk on my research in lithosphere deformation – it will have a title something like Deformation driven by deep and distant structures: influence of mantle lithosphere scarring in crustal tectonics. I’ll be presenting numerical modelling results using a numerical code called ASPECT. The code is a relatively new venture with quite big ideas about itself – which is the other reason why I am visiting. I’m keen to chat to the group to see if ASPECT could be used to supplement any existing studies/research programs. A main point of ASPECT is to be usable and extendible – I think it could be a great tool for the group at Imperial.
Examples of code output
A bit about the code
ASPECT stands for: Advanced Solver for Problems in Earth’s ConvecTion
It is written in a purposely extendible fashion, meaning it can be easily built on by different groups around the world – each adding something new and exciting to the code (which is written in C++).
It was built to support research in simulating convection in the Earth’s mantle and elsewhere. However, the latter part of the sentence is slightly misleading – as it sounds like it is only a code for mantle convection. ASPECT can also be used to simulate of lithosphere deformation (which is what I use it for).
The code generally runs on a supercomputer, but smaller simulations can be run on a desktop or even a laptop.
The code is free and developed out in the open (here, to be exact, so you can see what people are working on and what bugs there are). A big feature of ASPECT is that it is science-driven in it’s development – meaning that if lots of people are interested in developing rifting models or salt tectonic simulations, the code will be steered to incorporate all the nuanced parameters required. From the website:
It has grown from a pure mantle-convection code into a tool for many geodynamic applications including applications for inner core convection, lithospheric scale deformation, two-phase flow, and numerical methods development….
And it is still developing, it is not finished, and has a long way to go!
Another plus is that there is a pretty good mailing list. This sounds boring but it is really good – it is a venue for users to share problems and issues in the hope that other members of the community have either seen them and solved them, or can give advice on how to fix it.
You a fan of 2D? Or 3D better? ASPECT is built to extend a model dimensionally without too much difficultly.
What do you want to model – pick a geometry that is already built into the code: Box, box with lithosphere boundary conditions, chunk, ellipsoidal chunk, sphere, spherical shell, or unspecified!
Usable, Adaptable, and Extendable
The beauty of the code is that you can throw a lot at it. One example is apply seismic input to generate flow fields, to generate topography:
Basic setups as a starting point
At present, there are 30+ ‘cookbook’ examples that are available to use once the code is installed. Examples of interest include:
- 2D crustal model and 3D crustal model (as shown above)
- continental extension model (shown below)
- flow field and dynamic topography generation from seismic input
- prescribed plate boundary motion
The input files for these codes are easy to understand, and easy to change. I will go through the input file for the continental extension cookbook when I am visiting, as I think it will be a good starting point.
As described in the file – the cookbook is based off numerous published studies, including
- Brune, S., Heine, C., Perez-Gussinye, M., and Sobolev, S.V. (2014), Nat. Comm., v.5, n.4014, Rift migration explains continental margin asymmetry and crustal hyperextension
- Huismans, R., and Beaumont, C. (2011), Nature, v.473, p.71-75.
- Naliboff, J., and Buiter, S.H. (2015), Earth Planet. Sci. Lett., v.421, p.58-67
|The example is a 2D continental extension model 400 km x 100 km|
|There is a 0.25 cm/yr extension applied to the side walls and a restoring vertical velocity from the base of the model|
|It specifies an upper crust, lower crust, mantle lithosphere and seed|
|User specifies the temperature profile|
|Rheology: Non-linear viscous flow and Drucker Prager Plasticity|
|Values for most rheological parameters are specified for a background material and each layer|
|Values for viscous deformation are based on dislocation creep flow-laws, with distinct values for the upper crust (wet quartzite), lower crust (wet anorthite) and mantle (dry olivine).|
All these parameters can be modified easily by the user. Below are example of this input file that is ‘out of the box’ ready to use:
A low resolution video of the model can be seen below.
What is important: This starting input file can be quickly extended to 3D, increased in depth, and have the rheology changed.
Examples of published studies with ASPECT
Glerum et al. (2018) – Implementing nonlinear viscoplasticity in ASPECT: benchmarking and applications to 3D subduction modeling Solid Earth
Bredow et al. (2017) – How plume-ridge interaction shapes the crustal thickness pattern of the Réunion hotspot track G-cubed
Heister et al. (2017) High accuracy mantle convection simulation through modern numerical methods – II: realistic models and problems Geophysical Journal International
Gassmoeller et al. (2016) – Major influence of plume-ridge interaction, lithosphere thickness variations, and global mantle flow on hotspot volcanism-The example of Tristan G-cubed
Video caption: (top) Plume position, lithosphere thickness, topography;
(bottom) plume position, melt fraction, crust thickness for evolution of Tristan plume-ridge interaction (140 Ma to present)
It can be a bit of a pain to install, but with people on hand it can be simple. I’m available to help with installation and to create an installation guide – like the ones I’ve previously created. Another downside is that the code can take a little while to complete simulations.
A bit more about the code (links)
https://aspect.geodynamics.org – the software page.
Join the mailing list here! – it is an excellent way to get involved with the development and to voice questions.
Publications using ASPECT – from the software page.
ASPECT User Manual – updated regularly (currently 30 MB and 454 pages).
|What it is:||An extensible code written in C++ to support research in simulating convection in the Earth mantle and elsewhere.|
|Mission:||To provide the geosciences with a well-documented and extensible code base for their research needs.|
|Vision :||To create an open, inclusive, participatory community providing users and developers with a state-of-the-art, comprehensive software that performs well while being simple to extend.|
From the website:
ASPECT is a code to simulate problems in thermal convection. Its primary focus is on the simulation of processes in the earth’s mantle, but its design is more general than that. The primary aims developing ASPECT are:
- Usability and extensibility: Simulating mantle convection is a difficult problem characterized not only by complicated and nonlinear material models but, more generally, by a lack of understanding which parts of a much more complicated model are really necessary to simulate the defining features of the problem. This uncertainty requires a code that is easy to extend by users to support the community in determining what the essential features of convection in the earth’s mantle are.
- Modern numerical methods: We build ASPECT on numerical methods that are at the forefront of research in all areas — adaptive mesh refinement, linear and nonlinear solvers, stabilization of transport-dominated processes. This implies complexity in our algorithms, but also guarantees highly accurate solutions while remaining efficient in the number of unknowns and with CPU and memory resources.
- Parallelism: Many convection processes of interest are characterized by small features in large domains — for example, mantle plumes of a few tens of kilometers diameter in a mantle almost 3,000 km deep. Such problems require hundreds or thousands of processors to work together. ASPECT is designed from the start to support this level of parallelism.
- Building on others’ work: Building a code that satisfies above criteria from scratch would likely require several 100,000 lines of code. This is outside what any one group can achieve on academic time scales. Fortunately, most of the functionality we need is already available in the form of widely used, actively maintained, and well tested and documented libraries. Thus, ASPECT builds immediately on top of the deal.II library for everything that has to do with finite elements, geometries, meshes, etc.; and, through deal.II on Trilinos for parallel linear algebra and on p4est for parallel mesh handling.
- Community: We believe that a large project like ASPECT can only be successful as a community project. Every contribution is welcome and we want to help you so we can improve ASPECT together.