Pattern recognition of structural boundaries from aeromagnetic data using the 2-D continuous wavelet transform and the 3-D analytic signal

Abstract

The main goal of this paper is to use the 2-D continuous wavelet transform (CWT) combined with the 3-D analytic signal (AS) for structural boundaries delimitation from aeromagnetic data. The basic idea is based on the mapping of the maxima of the modulus of the 2-D CWT of the amplitude of the 3-D analytic signal (AS) for the full range of scales used to calculate the 2-D CWT. The proposed idea is applied to the synthetic data of a prism and a cylinder; obtained results show the power of this technique for contacts mapping in cases of high vector magnetization direction. Obtained results of the application to real aeromagnetic data of In Ouzzal area located in the west of Hoggar (Algeria) are compared with the 3-D analytic signal solutions. They show robustness of the proposed tool for pattern recognition of structural boundaries from potential geomagnetic data.

Minimum 60 years of recording are needed to compute the sea level rate of rise in the Western South Pacific

“…Suva-A, Fiji Along the coast of Australia, there is no acceleration of sea levels as already discussed [7][8][9][10][11]. Short time windows are responsible of apparently high rates of rise.…”

“…As previously reported in [11], the Sydney record is acceleration-free, as proved by the regular oscillations about the zero value of the time derivative of the rate of rise of sea levels compututed by using at all the times all the data collected so far. [20] show minimal differences, with small changes in positive or negative from one survey to the other in the rate of sea level rise.…”

“…The method is described in details in the references, in particular [7] and [11]. From a distribution of measured points x i , y i i=1,n where x is the time and y is the climate parameter of interest, the monthly average sea level or a climate index, the linear trend is first computed by linearly fitting the distribution.…”

“…It has been shown in recent papers, that all the long term tide gauges of the world recording the monthly sea levels since the latest 1800s -beginning of the 1900s consistently show periodic oscillations about an almost perfectly linear trend over the last century [4][5][6][7][8][9][10][11]. The longer of these oscillations have a quasi-60 year periodicity, and it has been suggested that what has been claimed as present sea level acceleration and presently higher than before rates of rise of sea levels is only the result of the selective focusing on the latest valley to peak movement of a multi decadal oscillation [4][5][6][7][8][9][10][11].…”

“…The longer of these oscillations have a quasi-60 year periodicity, and it has been suggested that what has been claimed as present sea level acceleration and presently higher than before rates of rise of sea levels is only the result of the selective focusing on the latest valley to peak movement of a multi decadal oscillation [4][5][6][7][8][9][10][11].…”