impact of goce on lithospheric modelling in active plate margins

Impact of GOCE on lithospheric modelling in active plate margins

ESA Living Planet Symposium 2013Edinburgh, 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

Integrated Modelling of Satellite and Airborne Gravity data of Active 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

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

(Götze et al., 2011)

revised gravity field information in geophysically interesting areas

impact on static and dynamic lithospheric models

Datasources – Terrestrial data

~ 175000 point measurements (gabs, 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

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

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

Datasources - Satellite gravity data

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

Available at:http://www.goco.eu/ (Mayer-Gürr et.al: The new combined

satellite only model GOCO03s, 2012)

The satellite only model GOCO03s

GRACE: 7.5 years

GOCE: 18 months

SLR: 5 years, 5 sat

CHAMP: 8 years

Constrains: Kaula, deg > 180

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

Validation of terrestrial data - Gravity

Difference terrestrial – GOCO03S (d/o 250) Difference terrestrial – EGM2008 (d/o 2190)

[mgal] GOCO03S EGM2008

Max. Diff 216.66 102.59

Min. Diff -325.72 -303.86

Mean -6.64 -1.45

RMS 24.08 10.94

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

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

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

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

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

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)

60

40

20

0

-20

-40

-60

mGal

60

40

20

0

-20

-40

-60

mGal

Results

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

Output field [mGal] Error estimates [mGal]

• Larger errors where only satellite data available (mainly omission part!!!)

• Realistic error estimates.

Restore & Validation with EGM2008

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

Restore (GOCO d/o 100 + topo-iso) IMOSAGA01C

Free-air anomalies Bouguer anomalies

IMOSAGA01C EGM2008

mGal

IMOSAGA01C EGM2008 difference

Restore & Validation with EGM2008

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

Restore (GOCO d/o 100 + topo-iso) IMOSAGA01C

mGal

difference

• Improved long-wavelength behaviour• Large differences in regions without

terrestrial gravity• Geophysical interpretation (Kiel)

IMOSAGA01C makes more sense

terrestr. input

Error estimates [mGal]

Lithospheric model (IGMAS+) - Iquique

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

Free-air anomalies Bouguer anomalies

IMOSAGA01C EGM2008

mGal

IMOSAGA01C EGM2008 difference

• Iquique: terrestrial gravity available

Lithospheric model (IGMAS+) - Iquique

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

• Only small variations compared to EGM2008• Lithospheric model could be confirmed

Lithospheric model (IGMAS+) - Beule

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

Free-air anomalies Bouguer anomalies

IMOSAGA01C EGM2008

mGal

IMOSAGA01C EGM2008 difference

• Beule: low-quality terrestrial gravity data

Lithospheric model (IGMAS+) - Beule

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

• Significant deviation to EGM2008• Updated lithospheric model required (currently done)

Lithospheric modelling

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

• 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!

Summary and conclusions

Significant improvement of regionalgravity field models through combinationof terrestrial and satellite dataMain benefit in areas with terrestrial data gaps, but also concerning the consistency in the long to medium wavelengthsProof of a clear impact of GOCE for lithospheric modelling, especially in topographically challanging regions

Methodology also usable for validation of inhomogenous gravity databasesEstablished 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

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

Final conclusion

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

GOCE rocks …