Joint gravity and magnetic inversion in 3D using Monte Carlo methods

Geophysics ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. G153-G156 ◽  
Author(s):  
Miguel Bosch ◽  
Ronny Meza ◽  
Rosa Jiménez ◽  
Alfredo Hönig
Keyword(s):  
Monte Carlo ◽  
Magnetic Susceptibility ◽  
Prior Information ◽  
3D Model ◽  
Mass Density ◽  
Magnetic Data ◽  
Gravity And Magnetic ◽  
Magnetic Inversion ◽  
Gravity And Magnetic Data ◽  
Model Layer

We jointly invert gravity and magnetic data following a Monte Carlo method that provides estimation for a 3D model of the structure and physical properties of the medium. In particular, the model layer geometry and the density and magnetic susceptibility fields within layers are estimated, and their uncertainties are described with posterior probabilities. This method combines the gravity and magnetic data with prior information of the mass density and magnetic susceptibility statistics, and statistical constraints on the model interface positions. The resulting model realizations jointly comply with the observations and the prior statistical information.

scholarly journals Unravelling the internal architecture of the Alnö alkaline and carbonatite complex (central Sweden) using 3D models of gravity and magnetic data

2017 ◽  
Author(s):  
Magnus Andersson ◽  
Alireza Malehmir
Keyword(s):  
Magnetic Susceptibility ◽  
Magnetic Anomaly ◽  
Bouguer Anomaly ◽  
Magnetic Data ◽  
Common Source ◽  
Gravity Gradients ◽  
Aeromagnetic Data ◽  
3D Inversion ◽  
Gravity And Magnetic ◽  
Magnetic Inversion

Abstract. The Alnö complex in central Sweden is one of the largest alkaline and carbonatite ring-shaped intrusions in the world. Presented here is the 3D inversion of ground gravity and aeromagnetic data that confirms some of the previous ideas about the 3D geometry of the complex but also suggests that the complex may continue laterally further to north than earlier expected. The gravity and aeromagnetic data show the complex as (i) a strong positiver Bouguer anomaly, around 20 mGal, one of the strongest gravity gradients observed in Sweden, and (ii) a strong positive magnetic anomaly, exceeding 2000 nT. Magnetic structures are clearly discernible within the complex and surrounding area. Petrophysical measurements (density, bulk magnetic susceptibility, and magnetic remanence) were used to constrain the 3D inversion. Both gravity and magnetic inversion models suggest that dense (> 2850 kg/m3) and magnetic (> 0.05 SI) rocks extend down to about 3.5–4 km depth. Previous studies have suggested a solidified magma reservoir at this approximate depth. The inversion models further suggest that two apparently separate regions within the intrusion with gravity and magnetic highs are likely connected at depth, starting from 800–1000 m, implying a common source for the rocks observed in these two regions. The modelling of the aeromagnetic data indicates that a more than 3 km wide ring-shaped magnetic high in the bay that can be a hidden part of the complex, linking a satellite intrusion in Söråker on the northern side of the bay to the main intrusion on the Alnö Island. While the rim of the ring must consist of highly susceptible rocks to support the magnetic anomaly, the centre has a relatively low magnetisation and is probably made up of low-susceptible wall-rocks or metasomatised wall-rocks down to about 2 km. Below this depth the 3D susceptibility model shows higher magnetic susceptibility values. From these observations the solidified magma chamber is interpreted to extend further to north than has previously been suggested.

Automatic 3-D interpretation of potential field data using analytic signal derivatives

Geophysics ◽  
1997 ◽  
Vol 62 (1) ◽  
pp. 87-96 ◽  
Author(s):  
Nicole Debeglia ◽  
Jacques Corpel
Keyword(s):  
Signal Amplitude ◽  
Vertical Gradient ◽  
Analytic Signal ◽  
Magnetic Data ◽  
Practical Implementation ◽  
Potential Field Data ◽  
Gravity And Magnetic ◽  
Second Derivatives ◽  
Gravity And Magnetic Data ◽  
Derivatives Of

A new method has been developed for the automatic and general interpretation of gravity and magnetic data. This technique, based on the analysis of 3-D analytic signal derivatives, involves as few assumptions as possible on the magnetization or density properties and on the geometry of the structures. It is therefore particularly well suited to preliminary interpretation and model initialization. Processing the derivatives of the analytic signal amplitude, instead of the original analytic signal amplitude, gives a more efficient separation of anomalies caused by close structures. Moreover, gravity and magnetic data can be taken into account by the same procedure merely through using the gravity vertical gradient. The main advantage of derivatives, however, is that any source geometry can be considered as the sum of only two types of model: contact and thin‐dike models. In a first step, depths are estimated using a double interpretation of the analytic signal amplitude function for these two basic models. Second, the most suitable solution is defined at each estimation location through analysis of the vertical and horizontal gradients. Practical implementation of the method involves accurate frequency‐domain algorithms for computing derivatives with an automatic control of noise effects by appropriate filtering and upward continuation operations. Tests on theoretical magnetic fields give good depth evaluations for derivative orders ranging from 0 to 3. For actual magnetic data with borehole controls, the first and second derivatives seem to provide the most satisfactory depth estimations.

3D inversion modeling of joint gravity and magnetic data based on a sinusoidal correlation constraint

2019 ◽  
Vol 16 (4) ◽  
pp. 519-529
Author(s):  
Xiu-He Gao ◽  
Sheng-Qing Xiong ◽  
Zhao-Fa Zeng ◽  
Chang-Chun Yu ◽  
Gui-Bin Zhang ◽  
...  
Keyword(s):  
Magnetic Data ◽  
3D Inversion ◽  
Gravity And Magnetic ◽  
Gravity And Magnetic Data

Application of gravity and magnetic methods to assess geological hazards and natural resource potential in the Mosida Hills, Utah County, Utah

Geophysics ◽  
2000 ◽  
Vol 65 (5) ◽  
pp. 1514-1526 ◽  
Author(s):  
Alvin K. Benson ◽  
Andrew R. Floyd
Keyword(s):  
Gravity Data ◽  
Magnetic Data ◽  
Geological Hazards ◽  
Mafic Lava ◽  
Subsurface Geology ◽  
Gravity And Magnetic ◽  
Geophysical Surveys ◽  
Utah County ◽  
Gravity And Magnetic Data ◽  
Hills Area

Gravity and magnetic data were collected in the Mosida Hills, Utah County, Utah, at over 1100 stations covering an area of approximately 58 km2 (150 mi2) in order to help define the subsurface geology and assess potential geological hazards for urban planning in an area where the population is rapidly increasing. In addition, potential hydrocarbon traps and mineral ore bodies may be associated with some of the interpreted subsurface structures. Standard processing techniques were applied to the data to remove known variations unrelated to the geology of the area. The residual data were used to generate gravity and magnetic contour maps, isometric projections, profiles, and subsurface models. Ambiguities in the geological models were reduced by (1) incorporating data from previous geophysical surveys, surface mapping, and aeromagnetic data, (2) integrating the gravity and magnetic data from our survey, and (3) correlating the modeled cross sections. Gravity highs and coincident magnetic highs delineate mafic lava flows, gravity lows and magnetic highs reflect tuffs, and gravity highs and magnetic lows spatially correlate with carbonates. These correlations help identify the subsurface geology and lead to new insights about the formation of the associated valleys. At least eight new faults (or fault segments) were identified from the gravity data, whereas the magnetic data indicate the existence of at least three concealed and/or poorly exposed igneous bodies, as well as a large ash‐flow tuff. The presence of low‐angle faults suggests that folding or downwarping, in addition to faulting, played a role in the formation of the valleys in the Mosida Hills area. The interpreted location and nature of concealed faults and volcanic flows in the Mosida Hills area are being used by policy makers to help develop mitigation procedures to protect life and property.

Sign in / Sign up

Export Citation Format

Share Document