GLOBAL SEISMIC TOMOGRAPHY

Jean-Paul Montagner Institut de Physique du Globe

Université Paris Diderot Institut Universitaire de France

ESE 2 april 2014

• Why? • Global tomography 1984->2014 • New Instrumentation • Computational Seismology: a New era • New discoveries • The future: what we need.

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A conception of the Earth some centuries ago

Athanasius Kircher, 1678

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Structure of the Earth Plate Tectonics Mantle Convection

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Global 3D- Earth Imaging: Fundamental constraints on the dynamic processes that drive plate tectonics, and on associated hazards (earthquakes, volcanoes,…)

Iron

Allo

y Si

licat

es

Jeanloz and Lay, 1993

PREM, Dziewonski and Anderson, 1981

1 D- model

The hardest thing of all is to find a black cat in a dark room (Confucius)

The hardest thing of all is to find a black cat in a dark room (Confucius)

Seismic Tomography

Woodhouse et al., 2004

Woodhouse and Dziewonski, 1984

SEMum

Lekic et al., 2011

Depth = 100 km

Data in Global & Regional Seismology

[www.iris.edu] [web.mst.edu]

[drh.edm.bosai.go.jp]

[www.geo.uib.no]

[data.earthquake.cn]

[Simons et al, 2006]

MERMAID/MariScope

ANR RHUM-RUM: OBS and Station Deployment (2012-2013)

Barruol et al., 2013

Time- Dependent Seismology: 3D-> 4D Noise correlations: Global scale (Hum)

ESE 2 april 2014 Nishida et al., Science, 2009

Verbeke et al., 2013

Noise correlations Regional Scale

Moho depth

Wagner et al., 2011

Subducting slabs – volcanic plumes

Stutzmann et al., 2006

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Central America

South Africa

New Discoveries • Body waves: Receiver function analysis

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Depth of “LAB” (Rychert et al, 2009) Thickness of LVL atop 410km discontinuity (Tauzin et al, 2009)

Surface waves

Burgos et al., 2014

New Discoveries: discontinuities in continental and oceanic lithospheres

ESE 2 april 2014

Yuan et al, 2011

Schmerr, 2012

Lekic et al, 2012, EPSL

Shear velocity Depth = 2800 km “LLSVP”

“Superplumes”

Lower mantle

# 1

# 500 all combined FLOPS: FLoating-point OPerations per Seconds

Latest trend: GPU computing

My Laptop

Courtesy of Jeroen Tromp

Era of Computational Seismology

1 billion (10 ) 9

(1 GigaFLOPS)

1 trillion (10 ) 12

(1 TeraFLOPS)

1 quadrillion (10 ) 15

(1 PetaFLOPS)

18 1 quintillion (10 )

(1 ExaFLOPS) 2018 − 2020

My iPhone

Titan, Cray (ORNL)

20 TeraFLOPS Your 2032 Laptop

Gig

aFLO

PS

Time (years)

Your 2032 iPhone

Adjoint Tomography and Full Waveform Inversion

European Crust & Upper Mantle • Transversely Isotropic Model EU30 • Anelastic Model EU50 • Azimuthally Anisotropic Model EU60

Rickers et al., 2013, EPSL

Other parameters: Anisotropy Depth 75 km

Zhu et al., Science, 2013

Better correlation with structural Geology

Samoa Hawaii Superswell Isosurface levels: -1% -> -3%%

French et al., 2013

Schmalzl and Ricard, 2008

A turbulent planet: comparison with fluid dynamics computations

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Imaging the Earth for better imagining

Modern methods of imaging now show the complexity and the variety of mantle dynamics (continents, slabs, plumes, …)

c

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What we need • Broadband arrays of uniformly calibrated instruments • Long-term ocean observatories and stations • Computational capabilities - HPC • Move from 3D to 4D seismology (time-dependent

seismology) • Training of next generation of researchers in

computational methods and wave propagation theory European tools for the next 10 years?

ESE 2 april 2014

The hardest thing of all is to find a black cat in a dark room, especially if there is no cat (Confucius)

But there might be

a dog

THANK YOU

ESE 2 april 2014

SEISMIC TOMOGRAPHY

Stutzmann et al., 2007

Subducting Plates

Shapiro et al., 2005

ESE 2 april 2014