A spectral analysis of geoid undulation and gravity anomaly data computed with Pratt's isostasy theory applied to Moho depth variations in Fennoscandia

Nord, Tomas; Sjöberg, Lars E.

doi:10.1111/j.1365-246x.1992.tb00564.x

Cited by 6 publications

(3 citation statements)

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“…Geoid undulation mapping has been done extensively over the sea surfaces using satellite-based altimetry (Rapp 1983;Engelis and Knudsen 1989;Zlotnicki 1993). Limited work has been done over the continents, mainly because of the lack of spheroidal heights over the continental surfaces, although gravimetrically determined geoids have been studied exhaustively (Milbert 1992;Sjoberg and Nord 1992;Rapp 1993;Sideris 1993;Lemoine et al 1997). The latest geopotential model, EGM96 (Lemoine et al 1997), was developed jointly by the NASA Goddard Space Flight Center, the National Imagery and Mapping Agency and the Ohio State University, using: (a) satellite tracking data as well as altimeter data from TOPEX, GEOSAT and ERS-1; (b) 30¢´30¢ terrestrial gravity data from National Imagery and Mapping Agency (NIMA) archives; and (c) 30¢´30¢ gravity anomalies derived from the GEOSAT Geodetic Mission altimeter data.…”

Section: Introductionmentioning

confidence: 99%

Geoid undulation modelling and interpretation at Ladak, NW Himalaya using GPS and levelling data

Banerjee

Foulger²,

Satyaprakash³

et al. 1999

Journal of Geodesy

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Abstract. Fast and accurate relative positioning for baselines less than 20 km in length is possible using dual-frequency Global Positioning System (GPS) receivers. By measuring orthometric heights of a few GPS stations by dierential levelling techniques, the geoid undulation can be modelled, which enables GPS to be used for orthometric height determination in a much faster and more economical way than terrestrial methods. The geoid undulation anomaly can be very useful for studying tectonic structure. GPS, levelling and gravity measurements were carried out along a 200-km-long highly undulating pro®le, at an average elevation of 4000 m, in the Ladak region of NW Himalaya, India. The geoid undulation and gravity anomaly were measured at 28 common GPS-levelling and 67 GPSgravity stations. A regional geoid low of nearly A4 m coincident with a steep negative gravity gradient is compatible with very recent ®ndings from other geophysical studies of a low-velocity layer 20±30 km thick to the north of the India±Tibet plate boundary, within the Tibetan plate. Topographic, gravity and geoid data possibly indicate that the actual plate boundary is situated further north of what is geologically known as the Indus Tsangpo Suture Zone, the traditionally supposed location of the plate boundary. Comparison of the measured geoid with that computed from OSU91 and EGM96 gravity models indicates that GPS alone can be used for orthometric height determination over the Higher Himalaya with 1±2 m accuracy.

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Section: Introductionmentioning

confidence: 99%

Geoid undulation modelling and interpretation at Ladak, NW Himalaya using GPS and levelling data

Banerjee

Foulger²,

Satyaprakash³

et al. 1999

Journal of Geodesy

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“…Discussions of the relation between the geoidal depression and the structure of the Moho were given in a series of studies, e.g. Sjöberg et al (1991, 1994), Nord (1992), and Nord & Sjöberg (1992). In these studies, an integral formulation and recent Moho maps were employed.…”

Section: Introductionmentioning

confidence: 99%

Structural effects of the crust on the geoid modelled using deep seismic sounding interpretations

Kakkuri

Wang

1998

Geophys. J. Int.

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According to the theory of isostasy, the Earth has a tendency to deform its surface in order to reach an equilibrium state. The land‐uplift phenomenon in the area of the Fennoscandian Shield is thought to be a process of this kind. The geoid, as an equipotential surface of the Earth’s gravity field, contains information on how much the Earth’s surface departs from the equilibrium state. In order to study the isostatic process through geoidal undulations, the structural effects of the crust on the geoid have to be investigated. The structure of the crust of the Fennoscandian Shield has been extensively explored by means of deep seismic sounding (DSS). The data obtained from DSS are used to construct a 3‐D seismic‐velocity structure model of the area’s crust. The velocity model is converted to a 3‐D density model using the empirical relationship that holds between seismic velocities and crustal mass densities. Structural effects are then estimated from the 3‐D density model. The structural effects computed from the crustal model show that the mass deficiency of the crust in Fennoscandia has caused a geoidal depression twice as deep as that observed from the gravimetric geoid. It proves again that the crust has been isostatically compensated by the upper mantle. In other words, an anomalously high‐density upper mantle must exist beneath Fennoscandia.

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“…Marquart (1993) seems (in her comment) to avoid the main problem, i.e. that it is almost impossible to correlate Moho depth with geoid undulation or gravity anomaly when one uses a better model [although the model for computing geoid undulation/gravity anomaly used in Sjoberg Nord and Faan (1991) and Nord & Sjoberg (1992) is far from perfect, it is more realistic than the model used in Marquart (1989)l to compute geoid undulation/gravity anomaly from Moho depths. These conclusions are the same independent of whether the comparison is made direct [as in Sjoberg et al (1991)] or in the spectral domain [as in Nord & Sjoberg (1992)l.…”

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Nord

Sjöberg

1993

Geophysical Journal International

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A spectral analysis of geoid undulation and gravity anomaly data computed with Pratt's isostasy theory applied to Moho depth variations in Fennoscandia

Cited by 6 publications

References 6 publications

Geoid undulation modelling and interpretation at Ladak, NW Himalaya using GPS and levelling data

Geoid undulation modelling and interpretation at Ladak, NW Himalaya using GPS and levelling data

Structural effects of the crust on the geoid modelled using deep seismic sounding interpretations

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