Importance of far-field topographic and isostatic corrections for regional density modelling. Issue 1 (20th July 2016)

• Record Type: Journal Article
• Authors: Szwillus, Wolfgang; Ebbing, Jörg; Holzrichter, Nils
• Is Part Of: Geophysical journal international. Volume 207:Issue 1(2016:Oct.)
• Page Start: 274
• Page End: 287
• Publication Date: 2016-07-20
• Subjects: Satellite geodesy -- Gravity anomalies and Earth structure -- Dynamics: gravity and tectonics; Geophysics -- Periodicals; 550
• DOI: 10.1093/gji/ggw270
• Languages: English
• ISSNs: 0956-540X

Abstract

Abstract: The long-wavelength gravity field contains information about processes in the sublithospheric mantle. As satellite-derived gravity models now provide the long to medium-wavelength gravity field at unprecedented accuracy, techniques used to process gravity data need to be updated. We show that when determining these long-wavelengths, the treatment of topographic-isostatic effect (TIE) and isostatic effects (IE) is a likely source of error. We constructed a global isostatic model and calculated global TIE and IE. These calculations were done for ground stations as well as stations at satellite height. We considered both gravity and gravity gradients. Using these results, we determined how much of the gravity signal comes from distant sources. We find that a significant long-wavelength bias is introduced if far-field effects on the topographic effect are neglected. However, due to isostatic compensation far-field effects of the topographic effect are to a large degree compensated by the far-field IE. This means that far-field effects can be reduced effectively by always considering topographic masses together with their compensating isostatic masses. We show that to correctly represent the ultra-long wavelengths, a global background model should be used. This is demonstrated both globally and for a continental-scale case area in North America. In the case of regional modelling, where the ultra-long wavelengths are not of prime importance, gravity gradients can be used to help minimize correction errors caused by far-field effects.