Research On The Algorithms For Forward Modeling Of Gravity And Magnetic Fields And Their Gradient Tensor For 2D Body

Gravity and Magnetic exploration is a geophysical exploration method that is based on the contrast of the property of the matter(density and magnetic susceptibility).The method has the advantage of high efficiency,easy operation,low cost,deep exploration depth,and has not many constraints for practical implementation.It has been applied in many fields,such as in the exploration of mental and non-mental,oil and gas,in rock and military engineering,cultural archaeology,deep crustal structure study.Restrained by measurement technology,the traditional gravity and magnetic exploration mainly study land gravity anomalies and total magnetic anomalies.In recent years,with the development of sensor technology and measurement technology,the single component measurement of the fields is replaced by multi-component measurement.High resolution and accurate measurement for gravity gradient tensor and magnetic gradient tensor have been developed.The range of measurement is from land to marine,airborne,logging.The large quantity of measurement data make it possible for density(magnetic susceptibility)fine inversion,so it has become a hot research point.Forward modeling is the foundation of the inversion.The efficiency of the inversion algorithm is mainly dependent on the efficiency of the forward modeling algorithm.For realizing rapid,fine inversion and imaging in the case of large quantity of measurement data,it is necessary to do research on forward modeling method.On this background,this thesis has further studied the forward modeling of gravity and gravity gradient tensor of two-dimensional(2D)body with arbitrary section shape and random density distribution,and the forward modeling of magnetic fields and magnetic gradient tensor of 2D body with arbitrary section shape and magnetic susceptibility distribution.The main work and achievement of the thesis is listed as follows.(1)A new algorithm for numerical computing 2D convolution-type integral is presented.The new algorithm is consisted of four parts: discretization scheme,computation of weight coefficients,rapid computation of one-dimensional discrete convolution,and summary of the fields.The four parts are a whole,where weight coefficient computation method guarantees the computational accuracy and one-dimensional discrete fast computational method ensures the computation efficiency of the whole algorithm.(2)Based on the new 2D convolution-type integral numerical algorithm,the details for forward modeling of gravity,gravity gradient tensor,magnetic fields,magnetic gradient tensor are given.Four simple 2D body models that have analytical expression for the fields are used to validate the new algorithms for forward modeling.The results show that the new algorithm has high computational accuracy and speed,and they have strong adaptability both for discontinuity and continuity of the distribution of the density or magnetic susceptibility.(3)Combining the new forward modeling algorithm and a interpolation scheme,the fast and accurate computation of the fields one the rugged curve in resolved.The research work of the thesis provide method support for the study on forward modeling,fast and fine density(magnetic susceptibility)inversion,and human-computer interactive modeling in the practical complex circumstance.