8 MagProc (original) (raw)

A combined analytic signal and Euler method (AN-EUL) for automatic interpretation of magnetic data

Geophysics, 2003

We present a new automatic method of interpretation of magnetic data, called AN-EUL (pronounced "an oil"). The derivation is based on a combination of the analytic signal and the Euler deconvolution methods. With AN-EUL, both the location and the approximate geometry of a magnetic source can be deduced. The method is tested using theoretical simulations with different magnetic models placed at different depths with respect to the observation height. In all cases, the method estimated the locations and the approximate geometries of the sources. The method is tested further using ground magnetic data acquired above a shallow geological dike whose source parameters are known from drill logs, and also from airborne magnetic data measured over a known ferrometallic object. In both these cases, the method correctly estimated the locations and the nature of these sources.

Chapter 7 Exploring and Using the Magnetic Methods

2017

The Earth is principally made up of three parts: core, mantle and crust (Fig. 1). As understood today, right at the heart of the Earth is a solid inner core composed primarily of iron. At 5, 700°C, this iron is as hot as the Sun’s surface, but the crushing pressure caused by gravity prevents it from becoming liquid. Surrounding this is the outer core, a nearly 2, 000 km thick layer of iron, nickel, and small quantities of other metals. Lower pressure than the inner core means the metal here is fluid. Differences in temperature, pressure and composition within the outer core cause convection currents in the molten metal as cool, dense matter sinks while warm, less dense matter rises. This flow of liquid iron generates electric currents, which in turn produce magnetic fields (Earth’s field). These convection processes in the liquid part of core (outer core) give rise to a dipolar geomagnetic field that resembles that of a large bar magnet aligned approximately along the Earth’s rotati...

The historical development of the magnetic method in exploration

GEOPHYSICS, 2005

The magnetic method, perhaps the oldest of geophysical exploration techniques, blossomed after the advent of airborne surveys in World War II. With improvements in instrumentation, navigation, and platform compensation, it is now possible to map the entire crustal section at a variety of scales, from strongly magnetic basement at regional scale to weakly magnetic sedimentary contacts at local scale. Methods of data filtering, display, and interpretation have also advanced, especially with the availability of low-cost, high-performance personal computers and color raster graphics. The magnetic method is the primary exploration tool in the search for minerals. In other arenas, the magnetic method has evolved from its sole use for mapping basement structure to include a wide range of new applications, such as locating intrasedimentary faults, defining subtle lithologic contacts, mapping salt domes in weakly magnetic sediments, and better defining targets through 3D inversion. These new...

Magnetics in geoexploration

Journal of Earth System Science, 1990

The magnetic method is the oldest and one of the most widely used geophysical techniques for exploring the earth’s subsurface. It is a relatively easy and inexpensive tool to employ, being applicable to a wide variety of subsurface exploration problems involving horizontal magnetic property variations occurring from near the base of the crust to within the uppermost meter of soil.

Magnetic Structure of the Earth’s Crust in the White Sea Region

International Journal of Geosciences, 2021

The geological structure of the White Sea area and the surrounding land areas has been well studied in the framework of individual case studies. There are a number of local models of the deep structure of the Earth's crust available. We propose a uniform assessment of deep crustal bodies responsible for long-period (regional) magnetic anomalies and consider their correlation with surface structures. The aim of the study is to build a three-dimensional magnetic model of the Earth's crust in the White Sea region using aeromagnetic data and modeling technologies of the Integro software package. The model is formed on the basis of a digital map of the anomalous magnetic field reduced to the pole. The sources of magnetic anomalies are considered to be located in the Earth's crust. The 3D distribution of the relative magnetic susceptibility of rocks was obtained by solving the inverse problem of the magnetic survey. To separate the magnetic sources by frequency and depth, it was necessary to continue the magnetic field of the model upward and to calculate the TDR derivatives, which determine the lateral boundaries of the sources of positive magnetic field anomalies. 2D distributions of magnetic sources of the model for vertical and horizontal sections with depths of 10, 15 and 20 km are analyzed. The correlation between the surface and deep structures of magnetic sources of the Earth's crust in the region is shown.

Eppelbaum et al Detailed magnetic paleomagnetic data analysis 2003

EAGE Annual Conference, 2003

Sea of Galilee (Lake Kinneret) is one of the main sources of fresh water in Israel. The sea is located in the area of complicated tectonic setting at the northern continuation of the Dead Sea Rift. Practical absence of wells in the Sea of Galilee basin sufficiently complicates geophysical data interpretation. Magnetic map of the total magnetic field of the sea area shows a complex pattern of the magnetic field distribution caused by a combined influence of the basalt flows surrounding this lake and magnetic sources occurring this sea. Positive and negative magnetic anomalies were recognized in the Sea of Galilee basin corresponding to the basalts of normal and reverse magnetization, respectively. These anomalies in the sea were investigated using modern procedures developed specially for complicated geological conditions. Applying these procedures quantitative parameters of the targets were determined and their classification was performed. A 3-D modeling of the magnetic field has been successfully carried out for refining the data obtained at the previous stage and to computing effects due to proposed geological boundaries and bodies. Developed paleomagnetic map of basalt associations framing Sea of Galilee basin was correlated with the paleomagnetic zones revealed in the sea. The recognized paleomagnetic zones in the sea basin basically are in accordance with the western and northern framing of the sea and have some disagreement with the eastern and southern framing. Analysis of radiometric and paleomagnetic data allowed us to conclude that in western part of the sea are developed Early Pliocene basaltic associations.