Theoretical Study on Stochastic Modeling of Combined Gravity-Magnetic-Electric-Seismic Inversion and Its Application

As gravity field, magnetic field, electric field and seismic wave field are all physical fields, their object function, reverse function and compound function are certainly infinite continuously differentiable functions which can be expanded into Taylor (Fourier) series within domain of definition and be further reduced into solving stochastic distribution function of series and statistic inference of optimal approximation. This is the basis of combined gravity-magnetic-electric-seismic inversion of stochastic modeling. It is an uncertainty modeling technology of combining gravity-magnetic-electric-seismic inversion built on the basis of separation of field and source gravity-magnetic difference-value (D-value) trend surface, taking distribution-independent fault system as its unit, depths of seismic and electric interfaces of interests as its corresponding bivariate compound reverse function of gravity-magnetic anomalies and using high order polynomial (high order trigonometric function) approximating to its series distribution. The difference from current dominant inversion techniques is that, first, it does not respectively create gravity-seismic, magnetic-seismic deterministic inversion model from theoretical model, but combines gravity-magnetic-electric-seismic stochastic inversion model from stochastic model; second, after the concept of equivalent geological body being introduced, using feature of independent variable of gravity-magnetic field functions, taking density and susceptibility related to gravity-magnetic function as default parameters of model, the deterministic model is established owing to better solution to the contradiction of difficulty in identifying strata and less test analytical data for density and susceptibility in newly explored area; third, under assumption of independent parent distribution, a real modeling by strata, the problem of difficult plane closure arising in profile modeling is avoided. This technology has richer and more detailed fault and strata information than sparse pattern seismic data in newly explored area, successfully inverses and plots structural map of Indosinian discontinuity in Hefei basin with combined gravity-magnetic-electric-seismic inversion. With development of high precision gravity-magnetic and overall geophysical technology, it is certain for introducing new methods of stochastic modeling and computational intelligence and promoting the development of combined gravity-magnetic-electric-seismic inversion to open a new substantial path.

Development of 3-D Gravity-Magnetic Models of the Earth’s Crust of Azerbaijan and Adjacent Areas: an Overview

Azerbaijan is located in the Alpine Himalayan collisional zone and is characterized by its complex and variable geological structure. To study Azerbaijan’s deep structure, twelve main regional interpreting profiles were selected for comprehensive 3D combined gravity-magnetic modeling. The development of the initial physical-geological models (PGMs) was based on known surface geology, drilling data, previous seismic, magnetotelluric and thermal data analysis, examination of the richest petrophysical data, as well as quantitative and qualitative gravity/magnetic data examination. The PGMs thus reflect the key structural-formational specifics of Azerbaijan’s geological structure, beginning from the subsurface (hundreds of meters) up to the Moho discontinuity (40 - 60 km). The PGMs revealed common factors controlling ore- and hydrocarbon bearing formations, primarily the boundaries of tectonic blocks, masked faults, and buried uplifts of magmatic rocks. Many of these factors can be used to investigate long-term geodynamic activity at a depth. The article summarizes many years of investigation by exemplifying the most typical PGMs for the Greater and Lesser Caucasus, the Kura depression, and central and northern Azerbaijan.

Structural Model of Kendeng Basin: A New Concept of Oil and Gas Exploration

Kendeng Basin stretches in an E-W direction from the Quaternary Merapi-Ungaran Volcano range in the West to the Madura Strait East of Jawa Timur Province, Indonesia. With Quaternary volcanic deposits covering this basin, its subsurface configuration has not been accurately identified. Several scholars suggest that its configuration forms an asymmetrical basin deepening to the south as a result of volcanic deposits and extending E-W direction. This paper answers what configuration Kendeng Basin has, including whether it consists of a simple asymmetrical shape as previous studies have interpreted or other patterns due to tectonic processes that took place during its formation. The research employed Gravity and Magnetic method, and the results were processed by spectral and gradient analyses. Both analyses revealed that Kendeng Basin formed Horst-Graben structures extending in an E-W direction based on a response to compression and strain forces during its formation. A structure with an E-W direction controls the shape of the Horst-Graben and is transected by a structural pattern extending in a NE-SW direction or known as the Meratus pattern. These findings provide an alternative to the concept of oil and gas exploration, which, until today, is merely known from the emergence of oil seepages in Kendeng Basin.