J. Ebbing & N. Holzrichter – University of Kiel Johannes Bouman – DGFI Munich Ronny Stolz –...
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J. Ebbing & N. Holzrichter – University of Kiel Johannes Bouman – DGFI Munich Ronny Stolz – IPHT Jena SPP Dynamic EarthPotsdam, 03/04 July 2014 Swarm &
J. Ebbing & N. Holzrichter University of Kiel Johannes
Bouman DGFI Munich Ronny Stolz IPHT Jena SPP Dynamic EarthPotsdam,
03/04 July 2014 Swarm & GOCE to reveal the dynamic and static
coupling within the lithosphere
GOCE data @ satellite altitude / Earths surface Signal @
satellite altitude is smooth Downward continuation enhances signal
power & details
Slide 7
Saudi Arabia Height 0 km10 km260 km Signal RMS 5.1 E4.1 E0.3 E
Model error 1.3 E0.9 E0.4 mE Omission error 83.5 E8.1 E0.2 mE V ZZ
degree RMS h = 0 & 260 km Downward continuation also amplifies
noise Effective resolution of data does not change Omission error
becomes much larger (mainly high frequency topography) Saudi Arabia
Height 0 km10 km260 km Signal RMS 5.1 E4.1 E0.3 E GOCO03S V ZZ
signal & error, L = 225 For model inversion it is probably best
to use data close to their original point of acquisition. GOCE data
@ satellite altitude / Earths surface
Slide 8
Inversion: Gz >90 km Z 0 =30 km = 350 kg/m 3 Moho depth by
gravity inversion
Slide 9
- satellite residuals - Inversion: Gz >90 km Z 0 =30 km =
350 kg/m 3
Slide 10
Inversion Gzz=Full Z 0 =30 km = 350 kg/m 3 Moho depth by
satellite gravity gradient inversion
Slide 11
Sensitivity of satellite gradients Z. Martinec 2013 Sensitivity
kernels for spherical gravity gradients
Slide 12
Improvement of Lithospheric Field Model... with present
satellites rsted and CHAMP... N = 60, resolution: 670 km... and
with Swarm N = 133, resolution: 300 km Magnetic field of Earths
crust radial component at 10 km altitude Before rsted... N = 30,
resolution: 1330 km
Slide 13
Poissons relation Magnetization of a tesseroid. The formula to
calculate gravity gradient tensor of a spherical prism (Asgharzadeh
et al., 2007), along with adaptive integration method (Li et al.,
2011) was used in software package called tesseroids- 1.1 (Uieda et
al., 2011; Uieda, 2013). By Poissons relation (Blakely, 1995) the
magnetic field is mathematically equivalent to the gradient of a
gravity field. Therefore, tesseroids was modified to calculate a
magnetic field. To this end the Earth crust is modelled by
spherical prisms with prescribed magnetic susceptibility and
remanent magnetization. Induced magnetizations are then derived
from product of the chosen main field model (such as International
Geomagnetic Reference Field) and the corresponding tesseroid
susceptibilities. Remanent magnetization vectors are directly set.
Spherical modelling tools
Slide 14
Numerical methods in comparison (Baykiev 2014)
TesseroidsSpherical caps Input: Crust1.0 Susceptibility of the
whole crust 0.04 SI Ambient field IGRF11 Grid resolution 2x2 deg
Grid altitude 400 km (also in Purucker et al. 2002)
Slide 15
Interpretation of magnetic anomalies Gradients along track can
be recovered from Swarm data (Kotsiaros Olsen 2013) Invariants of
gravity and magnetic field will help on polar regions to avoid
coordinate system dependency => Normalized source strength can
be used to describe lithospheric magnetization
Slide 16
A study area Why Greenland? Little geophysical data available
Mass estimates of changing ice sheets necessary for climate models
Coupling with physical state of lithosphere essential to estimate
dynamic behaviour Role of Iceland hotspot track?
Slide 17
Summary Analysis of satellite gravity data: lithospheric
structure Ice thickness vs. crustal thickness dynamic vs. static
components Analysis of satellite magnetic data: Characterization of
magnetic crustal thickness Normalized source strength for
describing tectonic domains Interpretation with DTU & GEUS
Implications for rheology Technical challenges: Magnetic gradients
along the track (with DTU) Tesseroids for complete magnetic tensor
modelling (with NGU) Implementation of invariant analysis in
inverse and forward modelling