Jökull


Jökull - 01.06.2000, Side 44

Jökull - 01.06.2000, Side 44
Foulger and Field Figure 7. (a) The Bouguer gravity field for the Krafla area reduced with a density of 2,300 kg/m3. The contour interval is 1 mGal. (b) The Bouguer gravity field de-trended by the removal of a regional gradient of 0.5 mGal/km. The mean of the data is 0 mGal and the contour interval is 1 mGal. Data are from Karlsdótt- ir et al. (1978). - (a) Bouguer þyngdarsvið á Kröflusvœði, skert við eðlisþyngdina 2,300 kg/m3. (b) Bouguer þyngdarsvið á Kröflusvœði að frádregnum svœðisstigli sem nemur 0.5 mGal/km. Mæligögnin erufengin frá R. Karlsdóttur ogfl. (1978). (Spector and Grant, 1970). The natural logarithm of the power spectrum is plotted against wavenumber in Figure 9, and the spectral gradient is -2zg. This ana- lysis yielded an estimate of Zg of 700 m below dat- um, or 300 m above sea level, confirming the rough estimate obtained using the half-widths of the anom- alies. An inversion was conducted to determine the density distribution required in a 1 km thick slab with its top surface at sea level (Figure 10). Density variati- ons up to ±150 kg/m3 are required. Inversions using thinner slabs required proportionately higher density contrasts, but much thicker slabs, which would require lower density contrasts, are ruled out by the power spectrum analysis. Densities higher than average are required beneath the NW, SW, SE and NE caldera rims and beneath Leirhnjúkur in the centre of the caldera. The latter is surrounded by material with density lower than average, and low density material is required south of the caldera. 42 JÖKULL No. 48

x

Jökull

Direkte link

Hvis du vil linke til denne avis/magasin, skal du bruge disse links:

Link til denne avis/magasin: Jökull
https://timarit.is/publication/1155

Link til dette eksemplar:

Link til denne side:

Link til denne artikel:

Venligst ikke link direkte til billeder eller PDfs på Timarit.is, da sådanne webadresser kan ændres uden advarsel. Brug venligst de angivne webadresser for at linke til sitet.