LITHOSPHERIC MODELLING BY USING OPTIMIZED GOCE GRAVITY GRADIENT DATA

摘要

The observed gravity and gravity gradient tensorrncomponents from the GOCE mission add newrndimension to the interpretation of lithospheric andrnmantle structure. Here we present two applications ofrnGOCE data to solid Earth modelling: For the MW=8.9rn11th March 2011 earthquake offshore Sendai, Japan,rnGOCE gravity data has been used as a regional field inrnorder to identify positive residual gravity anomaliesrnclose to the earthquake epicentre. Such anomalies arernsuspected of having significant influence on the stressrnregime of the subduction-zone interface. Concerningrndensity modelling, it is of much interest to investigaterndensity contrast and spatial distribution of the smallestrndensity anomalies detectable with the GOCErngradiometer system. Allowing for accuracies of a fewrnmE (1 milli-E?tv?s = 10e-12 1/s~2) and 1-1000 mGal (1rnmGal = 10e-5 m/s~2), we derived a relation for therndiameter of a density anomaly located below the Geoidrnas a function of density contrast. However, this methodrndoes not consider spatial resolution of the sampledrnGOCE data but rather takes the sensitivity of the systemrninto account. Thus, our results indicate what minimumrnsize and density contrast of the underlying geophysicalrnstructures are required in order to produce a signal ofrnthe order of GOCE's gradiometer sensitivity. Thesernfindings can have considerable impact on forwardrnmodelling and interpretation due to the fact that theyrnsuggest lower boundary conditions for the size ofrngeophysical structures to be modelled. Consequent 3Drndensity modelling tests with a synthetic model of thernChilean-Pacific convergent margin show that gravityrngradients and invariants upward continued to orbitrnheight clearly outperform the gravity field in terms ofrninformation yield on location and shape of anomalousrnstructures.