Impact of GOCE on lithospheric modelling in active plate margins

ESA Living Planet Symposium 2013 Edinburgh, 10-09-2013 Michael Hosse (1) , Roland Pail (1) , Martin Horwath (1) , Tetjana Romanyuk (1) , Ben Gutknecht (2) , Nils Köther (2) (1) Technische Universität München, Institute of Astronomical and Physical Geodesy (2) Christian-Albrechts-Universitaet Kiel, Institute of Geosciences, Department of Geophysics

About IMOSAGA I ntegrated Mo delling of S atellite and A irborne G ravity data of A ctive plate margins Part of DFG programme „Mass transport and mass distribution in the Earth system“ SPP 1257 Tight cooperation and interaction of geodetic and geophysical expert groups ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Project Objectives Investigation of active continental margins for – Density distribution in 3D – Dynamic Structures (Finite Elements) – Rigidity by usage of – Satellite gravimetry and gradiometry (GOCE, GRACE) – Terrestrial gravimetry – Combined gravity models (Least Squares Collocation LSC) ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Motivation revised gravity field information in geophysically interesting areas impact on static and dynamic lithospheric models

(Götze et al., 2011)

ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Datasources – Terrestrial data ~ 175000 point measurements (g abs , FA, BA) from different sources collected during the past 30 years widely spread over South America No informations available about used instruments and methods No accuracies available ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Datasources – Digital Terrain Model Used datasets: 3“ (land only) 30“ (with bathymetry) Available at: http://tethys.eaprs.cse.dmu.ac.uk/ACE2/ ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Validation of terrestrial data – Heights Differences to ACE2 – Max.: 915 m – Min.: -1365 m – Mean: 2.8 m – STD: 53.7m

ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Validation of terrestrial data – Heights Differences to ACE2 – Filtered at 80m (~25 mGal Free-Air) – Max.: 80 m – Min.: -80 m – Mean: 0.4 m – STD: 25,1 m ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Datasources - Satellite gravity data

The satellite only model GOCO03s

GRACE: GOCE: SLR: CHAMP: Constrains: 7.5 years 18 months 5 years, 5 sat 8 years Kaula, deg > 180 Available at: http://www.goco.eu/ ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013 (Mayer Gürr et.al: The new combined satellite only model GOCO03s, 2012)

Validation of terrestrial data - Gravity Difference terrestrial – GOCO03S (d/o 250)

[mgal]

Difference terrestrial – EGM2008 (d/o 2190)

GOCO03S EGM2008

Max. Diff 216.66

102.59

Min. Diff Mean RMS -325.72

-6.64

24.08

-303.86

-1.45

10.94

ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Calculation schema ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Calculation schema ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Calculation schema ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Preprocessing terrestrial data Dimension of normal equation depends on number of observations → restriction of points Distribution of points is very inhomogeneous Calculated for each of the 53.000 stations in study area Selected the stations with the smallest value q within a radius of 3 km ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Least Squares Collocation (LSC) … signal covariances, derived from covariance model fitted consistently to (reduced) gravity gradients and (reduced) terr. data … noise covariances: - terrestrial data: empirical - satellite gravity data: covariance propagation (including omission error !!!)

BIG

advantage: we obtain error estimates: ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Input data & stochastic models mGal 60 40 20 0 -20 -40

Satellite data (reduced):

• Synthetized from GOCO03S, on grid • Error information: - commission part: derived by full covariance propa gation from GOCO03S variance-covariance matrix - omission part (> d/o 250) : derived by variance propagation from EGM2008 variances -60 mGal 60 40 20 0

Terrestrial & altimetry data:

• Terrestrial data: 9910 points, irregularly distributed • Altimetry data (DTU10): 2353 points, on grid • Error information: according to quality criterion, ~10 mGal (land), ~4-5 mGal (ocean) -20 -40 -60 ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Results Output field [mGal] Error estimates [mGal] ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013 • Larger errors where only satellite data available (mainly omission part!!!) • Realistic error estimates.

Restore & Validation with EGM2008 Restore (GOCO d/o 100 + topo-iso) 

IMOSAGA01C

Free-air anomalies IMOSAGA01C EGM2008 Bouguer anomalies IMOSAGA01C EGM2008 difference ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013 mGal

Restore & Validation with EGM2008 Restore (GOCO d/o 100 + topo-iso) 

IMOSAGA01C

Error estimates [mGal] terrestr. input difference • Improved long-wavelength behaviour • Large differences in regions without terrestrial gravity • Geophysical interpretation (Kiel)  IMOSAGA01C makes more sense mGal ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Lithospheric model (IGMAS+) - Iquique •

Iquique: terrestrial gravity available

Free-air anomalies IMOSAGA01C EGM2008 Bouguer anomalies IMOSAGA01C EGM2008 difference ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013 mGal

Lithospheric model (IGMAS+) - Iquique • Only small variations compared to EGM2008 • Lithospheric model could be confirmed ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Lithospheric model (IGMAS+) - Beule •

Beule: low-quality terrestrial gravity data

Free-air anomalies IMOSAGA01C EGM2008 Bouguer anomalies IMOSAGA01C EGM2008 difference ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013 mGal

Lithospheric model (IGMAS+) - Beule • Significant deviation to EGM2008 • Updated lithospheric model required (currently done) ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Lithospheric modelling • In many regions due to lack of terrestrial gravity data up to now no lithospheric profile could be modelled by IGMAS+.

• In these regions, now due to GOCE data lithospheric modelling will become possible for the first time!

ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Summary and conclusions

Significant improvement

of regional gravity field models through

combination

of terrestrial and satellite data

Main benefit

in areas with terrestrial

data gaps

, but also concerning the consistency in the long to medium wavelengths

Proof of a clear impact of GOCE for lithospheric modelling

, especially in topographically challanging regions Methodology also usable for

validation

of inhomogenous

gravity databases

Established

processing procedure

can be applied

worldwide

(also with low-quality terrestrial data) Updated lithospheric models will be available soon ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013

Final conclusion ESA Living Planet Symposium 2013, Edinburgh, September 09-13 2013