3D seismic imaging of the earth’s mantle Barbara Romanowicz Department of Earth and Planetary Science U.C. Berkeley

Surface waves

P P S SS Surface waves Loma Prieta (CA) 1989 M 7 earthquake observed at KEV, Finland

Shearer, 1991 Global Transverse Component Stacks

After Park et al, 2005

Sumatra 12/26/04 M9.3 (0.8 to 2.2 mHz) CAN UNM 0S7 0S9 3S2 0S6 1S4 0S11 1S5 1S3 /3S1 0S8 0S5 0S0 200 hours starting 10 hours before origin time 0S10 0S12 mHz x10 0S5 0S13

PRELIMINARY REFERENCE EARTH MODEL (PREM) Dziewonski and Anderson, 1981 Radius [km] Solid Inner Core Liquid Outer Core Lower Mantle Upper mantle

( Albarède and van der Hilst, 1999

Van der Hilst et al., 1998 P-wave travel time tomography

SH SV S wave tomography

Montagner, 2002  = (Vsh/Vsv) 2 Seismic Anisotropy

Motivation for seismic Q tomography: Faul and Jackson, 2005

3D Shear Velocity Models

“SH models” “SV models” Gung et al., 2003

S velocity Model: SAW24B16

ABCD “ Pacific Superplume” Q -1 Hawaii

MNST African “superplume” Elastic SAW24B16 Q -1

Panning and Romanowicz, 2004 ISOTROPIC VELOCITY RADIAL ANISOTROPY  = (V SH /V SV ) 2

Wang and Wen, 2005 dlnVs ~ % Ni and Wen, 2005 African Superplume

Vs VV  Ishii and Tromp, 2000 Depth ~ 2800 km

Garnero, 1998

Courtillot et al., 2003

The Earth’s inner core

Anomalous splitting of core sensitive modes Data Model

Mantle mode Core mode

(Tanaka and Hamaguchi, 1995) Hemispherical dependence of anisotropy

Garcia and Souriau, 2002

Innermost Inner Core ? Ishii and Dziewonski, 2003

Differential rotation of the Inner Core

Published by AAAS J. Zhang et al., Science 309, (2005) Fig. 1. Ray paths of PKP waves and example of waveform doublet used to detect temporal change of travel times through the inner core

Published by AAAS J. Zhang et al., Science 309, (2005) Fig. 1. Ray paths of PKP waves and example of waveform doublet used to detect temporal change of travel times through the inner core

Published by AAAS J. Zhang et al., Science 309, (2005) Fig. 4. Difference of BC - DF times, d(BC - DF), at station COL as a function of the time separation between the two events of the doublet

Bréger et al., EPSL, 2000 Map: enhanced tomographic map at The core-mantle boundary STRONG MANTLE HETEROGENEITY?

Current Challenges Improving resolution of 3D structure: –Wave propagation in strongly heterogeneous 3D media/waveform inversion –Address uneven sampling (oceans) –Fine scale structure of major discontinuities Attenuation tomography 3D density structure Combining information from seismology, mineral physics, geochemistry and geodynamics

Cartoon from Cazenave, 2002

Garnero, Ann. Rev “Scenario for CMB”

Cartoon from Hellfrich and Wood, 2001

“SH models” “SV models”

Fukao et al., 2001

175 km 300 km Transverse isotropy dln   = Vsh/Vsv

km

Upper mantle:Q - lower mantle: Vsh Degree 2 only

QRLW8 Hotspot distribution Weighted by buoyancy flux Attenuation tomography

Anelastic attenuation: QRLW8 Gung and Romanowicz, 2002