geophysics and geodynamics in mainz

www.geophysik.uni-mainz.de

FKPE October 2012 Slide 1

Prof. Dr. Boris Kaus

Geophysics and Geodynamics in Mainz



Born (1976) & raised in the Netherlands 1997 Vordiplom RWTH Aachen 2001 Diplom ETH Zürich (Yuri Podladchikov) 2004 PhD ETH Zürich (Yuri Podladchikov) 2005-2006 Postdoc USC, Los Angeles (AG Thorsten Becker)

2007-2010 Oberassistent ETH (AG Tackley) 2010-2011 Assistant professor computational geodynamics ETH 9/2011- W2 Geophysik, Mainz

AWARDS 2005  ETH Medal for PhD thesis 2010  ERC Starting Grant 2011  Arne Richter Outstanding Young Scientists Award (EGU)

About me



Ins,tute of Geosciences in Mainz

8 W2/C3 professors 1 W3/C4 1 Heisenberg Professorship 1 W1 2 group leaders (including archeogeophysics)



•  Federführend bei abgelehnte Excellence-Cluster Antrag ERA (Earth and the Antropocene)

•  Research centers: – GEOCYCLES – COMPUTATIONAL SCIENCES

Ins,tute of Geosciences -‐ Research



•  Diplom Geowissenschaften – ~70 students left that need to be finished by 2014

•  BSc Geowissenschaften – 105 new students WS 12/13 (up from ~30 a few years ago) – 384 students in total

•  MSc Geowissenschaften – Started 1 year ago – only ~20 students

•  Starting SS2012: MSc Computational Sciences – open for BSc. Geophysics!

Studying in Mainz



– 1 Professor – 1 Assistant – 2 Postdocs – 5 PhD students – 3 Diplom students –  (still 3 PhD students @ ETH & 2 at USC)

Focus: – Geodynamic modelling –  Applied geophysics & Geothermics

Geophysics in Mainz



Ongoing research projects

Mantle convec,on Van Heck & Tackley (2008)

Surface processes

Interac,on mantle, lithosphere & surface processes.

Subduc,on ini,a,on & lithospheric failure

Subduc,on on present day & early Earth

Magma migra,on & emplacement BriVle crustal deforma,on

salt



•  Equations well established •  Typically need to be solved numerically •  Often reduced to variable viscosity Stokes problem

Equa,ons for mantle & lithosphere deforma,on

∂ui∂xi

= −1K⋅dPdt

conservation of mass

−ρgi = −∂P∂xi

+∂τ ij∂x j

conservation of momentum

εij =1

2ηeff

τ ij +1

2GDτ ijDt

+ λ ∂Q∂σ ij

visco-elasto-plastic rheology

ρc DTDt

=∂∂xi

k∂T∂xi

⎛⎝⎜

⎞⎠⎟+ Hsources conservation of energy

∂ui∂xi

= 0

−∂P∂xi

+∂∂x j

ηeff∂ui∂x j

+∂uj

∂xi

⎛

⎝⎜⎞

⎠⎟⎛

⎝⎜

⎞

⎠⎟ = −ρgi

K GGT 0

⎛

⎝⎜⎞

⎠⎟up

⎛

⎝⎜

⎞

⎠⎟ =

fg

⎛

⎝⎜

⎞

⎠⎟

Stokes flow



2D Lithospheric deforma,on: FEM -‐ MILAMIN_VEP

§  FEM code wriVen in MATLAB. §  Uses MILAMIN technology (Dabrowski et al. 2008) to speed up matrix assembly phase. §  Visco-‐elasto-‐plas,c rheology. §  Unstructured OR structured finite elements. §  Q1P0, Q2P-‐1, T2P-‐1. §  Free surface. §  Thermo-‐mechanical coupling. §  Tracer-‐based or contour-‐based material proper,es §  Lagrangian with remeshing for large deforma,ons §  Phase transi,ons. §  Disadvantages: 2D only, serial, uses direct solvers.



•  3D only, written in C, uses PETSc (fully MPI parallel). •  Runs on massively parallel computers (>16’000 cores on JUQUEEN, at the

Forschungszentrum Jülich) •  Use either a finite element OR a finite difference discretization. •  Uses multigrid methods – lot’s of research on making them work..

FEM – LaMEM (Lithosphere and Mantle Evolu,on Model)



Can we constrain the rheology & dynamics of the crust on geological ,mescales?

Zagros Mountains, Iran



Zagros



Zagros – geological constraints



•  For folding to occur, q>20 •  Observations:

λ~14.4 km, Hsed~7.8 km èn>23.

•  Very large power law exponent. => Indication that the overburden deformed in a brittle manner.

So let’s apply theory for detachment folding

λ = 3.1 ηsed

nηsalt

⎛⎝⎜

⎞⎠⎟

16 Hsalt

Hsed

Hsed

q = 2.5n ηsed

nηsalt

⎛⎝⎜

⎞⎠⎟

13 Hsalt

Hsed

⎫

⎬

⎪⎪⎪

⎭

⎪⎪⎪

q = 2.5n λ3.1Hsed

⎛⎝⎜

⎞⎠⎟

2

e.g., Schmalholz et. al (2002)

Dom. Wavelength:

Dom. Growthrate:

Hsed/2

Hsalt ηsalt

n,ηsed



Homogeneous briVle overburden

Faul,ng an

d not foldi

ng!



A more detailed look at the stra,graphy

Several (thin) detachment layers within the overburden.



With 4 weak layers

Folding rath

er then fau

l,ng.

Wavelength

& ,ming co

nsistent wi

th constra

ints



What about the physics? Hsed/2

Hsalt ηsalt

n,ηsed

What about the physics?



Mul,ple intra-‐crustal detachment layers strongly favor folding!

What about the physics?



Yamato, Kaus, Mouthereau, Castelltort (2011) Geology

Constraining rheology from natural observa,ons

•  Very small effec,ve fric,on angle ! Why?



Evidence from recent seismo-‐tectonics

EPSL, 2010



What about 3D?


FKPE October 2012 Slide 24 1024 cores of the BlueGene/P (Lausanne) or Cray XT5 (Swiss Supercompu,ng Center)

27x512x512 nodes



•  The regular spacing of folds in the Zagros gives constraints on crustal-scale rheology.

•  Zagros: weak detachment layers in sedimentary overburden are required.

•  Zagros: the effective friction angle <5°. High fluid pressures? Does the presence of oil lubricate deformation on geological timescales?

Crustal-‐scale rheology -‐ summary



Requires a visco-elasto-plastic two-phase flow formulation

Melt migra,on & lithospheric deforma,on



•  A two-phase flow visco-elasto-plastic melt migration formulation results

Melt migra,on

diapirs channels ‘dikes’

Preliminary results

Keller et al. (submiVed to GJI)



Numerical models of subduc,on ini,a,on

Thielmann & Kaus, EPSL (2012)



Geodynamic inverse modelling

•  Parallel forward model •  Parallel neighborhood algorithm of Sambridge •  Joint inversion with geodynamic & gravity models

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log10

(!sediment

in Pa s)

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sity

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log10

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log

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! salt in

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s)

log

10(m

isfit

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(!salt

in Pa s)

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/m3

log

10(m

isfit

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!0.5

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(!sediment

in Pa s)

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/m3

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10(m

isfit

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!1

!0.5

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4

Baumann et al. (in prep)



Erosion and tectonics

High resolu,on erosion model

Constraints from the Zagros

3D crustal deforma,on model



Net-‐rota,on of the lithosphere

HS3: ~4.9 cm/year Most other models: ~1-‐2 cm/yr

Why do the Earth’s plates move westwards?

Predicted net rota,on Measured

net rota,

on

Gerault et al. (2012) G-‐cubed, Vol 13 (4), April 2012



Thin sheet & 3D collision

Lechmann et al. Geophysical Journal Interna,onal (2011)



•  Geodynamics is a very active research field. •  Numerous unsolved problems, particularly

related to lithosphere and crustal dynamics •  This requires – Developments in numerical codes – Understanding the physics in the codes – Talking to other geoscientists

•  Mainz is the place to be…

Conclusions

geophysics and geodynamics in mainz

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