Download Application cases of the offer Magnetic inversion

Application cases of the offer
Magnetic inversion
The interpretation of the anomalous magnetic field (nT) for the site is considered for
Bakhchisaray district of Crimea. Sub latitudinal profile AB passes through intrusive body (Fig. 1)
across its strike. Step between the points of measurement of the magnetic field equals 5 meters. This
distance was used to size cubes that filled geological section. This approach applies to grid method.
Inversion is a calculation of the magnetization of each cube from the magnetic field. The method of
gradual approximation of random is applied which the easiest to use. Vertical incision has a depth
of 40 m, and its length is 145 m (Fig. 2).
Б
А
Fig. 1. Sub latitudinal profile (AB) of magnetic observations
Fig. 2. Calculation of magnetization module for profile AB
Geological rocks stacked from rocks of Karadag series and Bodraksky complex that belong to
middle Jurassic (J2kd). Karadag series presented the alternation of tuff-sandstone, tuff-siltstone and
tuff-mudstone. Bodratsky complex of small intrusions compiled from diabase. Magnetic inversion
was the basis for the construction of geological section (Fig. 3).
tuff-sandstone,
tuff-siltstone &
tuff-mudstone
diabase
діабаз
и
Fig. 3. Geological section according to the geological survey and magnetic inversion
Magnetic inversion gave the geometry and direction of the fall of the intrusive body.
Similarly, we can perform a gravity inversion to study the density distribution in depth.
Gravity modeling
The essence of gravitational modeling is construction of layer geometry with a given density.
Initial data is consisted from gravitational anomalies or free air anomalies, density of layers and
bathymetry data. Research profile crossed the Terceira Rift that is located between the Eurasian and
African plates. The main focus was on determining the thickness of sediments in the Azores (Figure
4). Profile of research is highlighted white arrow.
Fig. 4 Total tectonic structure Azores archipelago
Profile for interpretation has a length of 133 km of azimuth 45°. Bathymetry data correspond
to top of sediments and basaltic crust layer. Strike of layers was set equal to infinity in modeling.
The value for density layers (in g/cm3), the following: water (1.03), sediment (2.1), the oceanic
crust (2.8-3.0) and mantle (3.1-3.3). Isostatic principle is applied in the first stage of modeling. It is
characterized the uniform pressure geological unit at the depth of 65 km for different combinations
of density and thickness of the layers. Total section for layers was obtained as a result. Top layer
with a density of 2.8 g/cm3 was changed to best match the observed anomalies with a model in the
second phase. Simulation results have found that sedimentary rocks are synclinal structure and the
surface of the mantle beneath them is anticlinal form (Figure 5). This rift zone is perspective for
search for hydrocarbon deposits. Results interpretation agreed with basic understanding of the
geological structure of territory.
g, mGal
Water ρ=1.03 g/cm3
Sediments
ρ=2.1 g/cm3
observed
modeled
Crust ρ=2.8 g/cm3
ρ=3.0 g/cm3
Mantle ρ=3.1 g/cm3
ρ=3.3 g/cm3
Fig. 5. Modeling of geological section using isostatic compensation of rocks and fitting of layers geometry