CN101937106B - Method for processing magnetic survey data of seafloor macrorelief survey lines - Google Patents

Abstract

The invention provides a method for processing magnetic survey data of seafloor macrorelief survey lines. The method comprises the following steps of: acquiring the magnetic survey data of a seafloor target area, the position data of magnetic survey points and seafloor topographical data; based on the acquired seafloor topographical data, performing 3D grid division on the seafloor target area to establish a magnetic parameter model; establishing a target inversion function showing an error between a magnetic anomaly theoretical value and an observation value, and modifying a magnetic parameter by taking the minimum value of the target inversion function as a fitting standard; and finally working out a magnetic anomaly parameter of the target area according to the magnetic parameter obtained by inversion. In the method, upward continuation, high-stop filtering and the conversion of the observation data on a relief surface into that on a horizontal surface are unnecessary, so that a middle process causing resolution reduction is avoided; and the inversion of the magnetic survey data is carried out by a 3D spatial domain combined topographical direct inversion method, the resolution is improved, the relief energy of the observation points is not limited, so that the method is applied to the seafloor magnetic survey of the macrorelief survey lines.

Description

A kind of seabed macrorelief survey line magnetic survey processing method of data

Technical field

The present invention relates to submarine geophysics exploration engineering field, relate in particular to a kind of seabed macrorelief survey line magnetic survey processing method of data.

Background technology

Along with the day of global resources is becoming tight, since the eighties in last century, countries in the world are all transferred to sight on the ocean gradually, have begun the exploration energetically to the marine field resource.Magnetometer survey is a kind of irreplaceable important detection means in the geophysical survey, mainly contains aviation, ground, sea and seabed magnetic survey.

Theoretically, several kinds of magnetic survey modes do not have essential distinction.But say that from exploration engineering, method and exploration effects characteristics are respectively arranged.Because inverse square law is satisfied in the magnetic source field, magnetic survey resolution and exploration effects depend on that the source receipts are apart from (distance between objective body and observation station).Airborne magnetic survey efficient is high, not limited by the region, but because receive apart from receiving apart from big than the source of ground magnetic survey and seabed magnetic survey in the source, the relative ground of resolution and seabed magnetic survey are low, are fit to generally investigate on a large scale.The ground magnetic survey is the simplest and easy, exploration effects is best, but limited by the region.Magnetic survey method in sea is similar with the ground magnetic survey; Its exploration targets body is below the seabed; Receive apart from much larger than aviation and ground magnetic survey in the source of sea magnetic survey, so resolution compares airborne magnetic survey with exploration effects and the ground magnetic survey is relatively poor, is fit to marine site investigation and geology of deep part research.Receive apart from receiving apart from much little than the aeromagnetic source on sea magnetic survey and the marine site in the source of seabed magnetic survey; The sea magnetic survey is compared in the seabed magnetic survey will improve exploration effects and resolution greatly; Be that airborne magnetic survey and sea magnetic survey are irreplaceable; Can provide unique imaging technique such as submarine volcano, hydrothermal activity, sulfide, metalliferous deposit, be with a wide range of applications.

But the seabed magnetic survey is very complicated on observation technology with respect to airborne magnetic survey and sea magnetic survey, and difficulty is very big.As shown in Figure 1, compared the magnetic survey line of several kinds of magnetic survey modes.Wherein, airborne magnetic survey is by the magnetic data of carrying magnetometer measurement flight range aboard.Because flight rises and falls and generally do not surpass tens meters during magnetic survey, the fluctuation range of its magnetic survey line is very little.Equally, the sea magnetic survey is in same plane by the magnetic data of carrying the magnetometer measurement navigation area on research ship because the sea it is generally acknowledged, its magnetic survey line is more level and smooth than the magnetic air survey line.And magnetometer generally is encapsulated in the pressure-resistant cabin in the magnetic survey of seabed, pressure-resistant cabin be placed on research ship between in the seabed towed body that is connected with hawser.Magnetic survey point position is just confirmed by the towed body position like this; But because the general more complicated of deep-sea sea situation; The towed body position can stably be controlled unlike the research ship that kind on aeromagnetic aircraft or sea, and it is very big to cause point position to rise and fall, and rises and falls between measuring point to reach on the hundreds of km even several kilometers.Cause the fluctuation of seabed magnetic survey line violent.The oceanic ridge seabed is with a varied topography simultaneously, and its outline line rises and falls also very violent.Can not utilize airborne magnetic survey or land magnetic survey existing conventional to handle for magnetic survey data, handle seabed magnetic survey data like technology such as continuation, Qu Huaping, inversion interpretations, otherwise possibly obtain wrong result with this characteristic.

This has proposed new research topic for seabed magnetic survey data processing inversion interpretation technology, presses for the relevant seabed of development and surveys fundamental researches such as data processing method, technology.Therefore carry out that seabed magnetic survey work has important practical significance and significant to the magnetometer survey theoretical developments.This similar technology mainly carries out two in frequency field abroad at present, 3-d inversion, and they need filtering, upward continuation, requirement that observation data is transformed on the surface level, and these can lose high-frequency signal and reduce resolution.

Summary of the invention

The present invention is intended to be directed against seabed, deep-sea magnetic survey data and has characteristics such as point position rises and falls especially greatly, submarine topography complicacy; Can not observation data be transformed on the certain level face with existing songization quadratic method; Thereby can't carry out data processing and this problem of inversion interpretation with existing conventional method, a kind of direct inversion method of spatial domain band landform 3D that is suitable for the seabed magnetic survey data of this characteristic is provided.

A kind of seabed macrorelief survey line magnetic survey processing method of data comprises:

(1) obtains magnetic survey data, magnetic survey point position data and submarine topography data;

In the magnetic survey of seabed; The magnetic survey data are obtained by the magnetometer collection in the towed body, and towed body is placed in the deep-sea, and are connected with hawser between the research ship; Magnetic survey point position is the position of towed body, and the submarine topography data are gathered by the underwater positioning device on the research ship (like sonar etc.) and obtained;

(2) 3D grid is carried out in the sub-sea floor targets zone and divide, set up the magnetic parameter model;

Submarine topography data according to obtaining are divided into several 3D grids with the submarine topography profile, are the measuring point of a magnetic data like each unit grids.Then submarine topography can be by the combination approximation of 3D grid, and the grid number of division is many more, and is accurate more to being similar to of submarine topography profile.

Set up the theoretical model of magnetic parameter to the 3D grid after dividing, model is represented that by math equation equation can be written as:

$g_{\mathrm{ij}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{a}_{\mathrm{ij}}{\mathrm{\σ}}_{\mathrm{ij}}$

Wherein, m, n represent the ranks number of 3D grid, g respectively _Ij(it is the theoretical value of model equation for i, the j) magnetic anomaly of individual grid, a in expression the _IjExpression magnetic anomaly g _IjTo (i, j) individual unit grid magnetic parameter σ _IjPartial derivative.

(3) setting up the target inverting function of seabed magnetic survey data, is the match standard with target inverting function minimum, revises magnetic parameter;

Target inverting function representation is:

$F=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(g_{\mathrm{ij}}^{\′}-g_{\mathrm{ij}})}^2$

In the formula, g _Ij(in fact target inverting function has reflected the theoretical value of magnetic anomaly and the error between the observed reading for i, the j) observed reading of the magnetic anomaly on the individual grid in expression the.At first rule of thumb provide the magnetic parameter initial value of each unit grid; Calculate the magnetic anomaly initial value; Then magnetic parameter is constantly revised, index word generally adopts the generalized inverse method to find the solution, and is minimum up to the value of target inverting function; The theoretical value and the error between the observed reading of expression magnetic anomaly are minimum, and the magnetic parameter model equation of this moment reaches inversion theory match standard.

(4) magnetic parameter that is obtained by inverting calculates the magnetic anomaly of target area.

The inventive method does not need the seabed survey line is carried out upward continuation, high cut filtering or the observation data on the relief is transformed on the surface level; Avoided causing the pilot process of resolution reduction; Utilize the three dimensions territory direct method of inversion of band landform to the magnetic survey data inversion; Not only improve resolution, and the relief volume of point position has not been limited, be applicable to the seabed magnetic survey of macrorelief survey line.

Description of drawings

Fig. 1 is the characteristic comparison diagram of several kinds of magnetic survey mode gained magnetic survey lines;

Fig. 2 is the process flow diagram of the inventive method;

Fig. 3 is for to be divided into three-dimensional element grid synoptic diagram with submarine topography.

Embodiment

Below in conjunction with accompanying drawing, specify the practical implementation process of the inventive method.

As shown in Figure 2, macrorelief survey line magnetic survey processing method of data in a kind of seabed of the present invention comprises:

(1) obtains sub-sea floor targets regional magnetic survey data, magnetic survey point position data and submarine topography data;

In the magnetic survey of seabed, the magnetic survey data are obtained by the magnetometer collection in the towed body, and towed body is placed in the deep-sea; Be connected with hawser between the research ship; Magnetic survey point position is the position of towed body because the random fluctuation property of sea ocean current, make towed body can be under the affecting of hawser dipping and heaving; And make that the magnetic survey line that magnetometer the obtained fluctuation in the towed body is comparatively violent, as shown in Figure 1.The magnetic survey data have constituted seabed magnetic survey macrorelief survey line, and it is complicated curved surface.The submarine topography data are gathered by the underwater positioning device on the research ship (like sonar etc.) and are obtained.

(2) 3D grid is carried out in the sub-sea floor targets zone and divide, set up the magnetic parameter initial model;

According to the submarine topography data submarine topography profile is divided into several regular rectangular parallelepiped grids, as shown in Figure 3, the length of rectangular parallelepiped grid end face and width are confirmed as known quantity according to concrete conditions such as goal in research regional extent and research requirements.If the submarine topography big rise and fall, length and width that can the grid end face be set to less value, like this target area are divided into more grid, and raising is to the fitting precision of complex-terrain.If submarine topography is more smooth, length and width that then can the grid end face be set to bigger value.The z axial coordinate of rectangular parallelepiped end face is got corresponding seabed depth here, and the grid height is confirmed through the z axial coordinate of grid end face and the difference of bottom surface buried depth, and the bottom surface buried depth of rectangular parallelepiped grid is confirmed according to geology, geophysics and other data.Then submarine topography can be by the end face approximate representation of rectangular parallelepiped unit grid as a point position at each unit grid center, and the grid number of division is many more, and is accurate more to being similar to of submarine topography profile.

Theoretical according to potential field, the magnetic anomaly that seabed magnetic survey macrorelief survey line constitutes on any complex-curved can be superposeed by the measuring point magnetic anomaly of each unit grid and obtain, and the magnetic anomaly on the seabed magnetic survey line curved surface can be represented with following model equation:

$g_{\mathrm{ij}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{a}_{\mathrm{ij}}{\mathrm{\σ}}_{\mathrm{ij}}---\left(1\right)$

Wherein, m, n represent that the grid of being divided has the capable n row of m, σ _IjExpression the (i, the j) magnetic parameter of individual grid, like the magnetization or magnetic susceptibility etc., g _Ij(it is the theoretical value of model equation for i, the j) magnetic anomaly of individual measuring point, a in expression the _IjExpression magnetic anomaly g _IjTo (i, j) individual unit grid magnetic parameter σ _IjPartial derivative.Formula (1) can be write as matrix form:

G＝A·B (2)

Wherein, G is illustrated in the magnetic anomaly model equation theoretical value g that each measuring point is obtained by formula (1) _IjThe magnetic anomaly matrix of forming, A are magnetic anomaly matrix G to the, and (B is each grid magnetic parameter σ for i, the j) partial derivative matrix formed of the partial derivative aij of individual unit grid magnetic parameter _IjThe magnetic parameter matrix of forming has respectively:

$A=\left[\begin{array}{cccc}{a}_{11}& a_{12}& ...& a_{1(m\×n)}\\ a_{21}& a_{21}& ...& a_{2(m\×n)}\\ .& .& .& .\\ .& .& .& .\\ .& .& .& .\\ a_{m1}& a_{m2}& ...& a_{m(m\×n)}\end{array}\right]$

G ^T＝[g ₁₁ g ₁₂ … g _1n g ₂₁ g ₂₂?… g _2n?… g _m1 g _m2?… g _mn]

(3)

B ^T＝[σ ₁₁?σ ₁₂?…?σ _1n?σ ₂₁?σ ₂₂?…?σ _2n?…?σ _m1?σ _m2?…?σ _mn]

Wherein, T representes transposition.

(3) setting up the target inverting function of seabed magnetic survey data, is the match standard with target inverting function minimum, constantly revises magnetic parameter;

The inverting objective function F can be written as:

$F={(G^{\′}-G)}^2=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(g_{\mathrm{ij}}^{\′}-g_{\mathrm{ij}})}^2---\left(4\right)$

In the formula, G ' is illustrated in the magnetic anomaly g ' that each measuring point observation obtains _IjThe matrix of forming.According to inversion theory; Observing the 3D magnetic anomaly inverting on the curved surface arbitrarily at macrorelief is exactly the magnetic parameter of confirming each unit grid; Magnetic parameter by each unit grid matches with the magnetic anomaly data that observation obtains through the resulting magnetic anomaly of stack summation; Make the match difference between Theoretical Calculation result and the observed result minimum, make that the value of inverting objective function F is minimum.

Minimal value by formula (3) is following for the match standard can get inversion equation:

ΔG＝A·ΔB (5)

Wherein, Δ G=G '-G, Δ B are the index word Δ σ of each unit grid magnetic parameter _IjThe matrix of forming:

ΔB ^T＝[Δσ ₁₁?Δσ ₁₂?…?Δσ _1n?Δσ ₂₁?Δσ ₂₂?…?Δσ _2n?…?Δσ _m1?Δσ _m2?…?Δσ _mn](6)

At first, rule of thumb provide the initial guess B of magnetic parameter matrix B ₀, find the solution can win time magnetic parameter model modification amount Δ B of formula (3) by the generalized inverse method ₀, by B ₁=B ₀+ Δ B ₀Obtain the magnetic parameter matrix after the iterative modifications for the first time.Then with B ₁As new initial model parameter, obtain second revision amount Δ B by the generalized inverse method equally ₁Repeat above process, up to the k time model parameter index word Δ B _K-1, according to following iterative formula the magnetic parameter matrix is made amendment then, minimum up to the value of inverting objective function F.

B _k＝B _k-1+ΔB _k-1(k＝1，2，3...)(7)

(4) by the magnetic anomaly on a certain height levels of magnetic parameter Model Calculation that obtains after the inverting or the curved surface.

The process of being calculated the magnetic survey data by the inventive method need not the operation through continuation or Qu Huaping; But after calculating final magnetic survey data model equation by the inventive method; Can the magnetic survey data being developed equally, (continuation face is generally the certain level face to any continuation face; As shown in Figure 1), only need are imported the position coordinates of continuation face in model equation, can calculate the magnetic response value of continuation face very easily.

Claims (1)

1. a seabed macrorelief survey line magnetic survey processing method of data is characterized in that, comprising:

(1) obtains sub-sea floor targets regional magnetic survey data, magnetic survey point position data and submarine topography data;

(2) 3D grid is carried out in the sub-sea floor targets zone and divide, set up the magnetic parameter model;

(3) setting up the target inverting function of seabed magnetic survey data, is that the match standard is constantly revised magnetic parameter with target inverting function minimum;

(4) magnetic parameter that is obtained by inverting calculates the magnetic anomaly of target area;

Described magnetic parameter model is:

$g_{\mathrm{ij}}=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{a}_{\mathrm{ij}}{\mathrm{\σ}}_{\mathrm{ij}}$

Wherein, m, n represent row, the columns of grid, g respectively _IjExpression (i, the j) magnetic anomaly of individual grid, σ _IjExpression (i, the j) magnetic parameter on the individual grid, a _IjExpression magnetic anomaly g _IjTo magnetic parameter σ _IjPartial derivative;

Described target inverting function is:

$F=\underset{i=1}{\overset{m}{\mathrm{\Σ}}}\underset{j=1}{\overset{n}{\mathrm{\Σ}}}{(g_{\mathrm{ij}}^{\′}-g_{\mathrm{ij}})}^2$

Wherein, g ' _IjExpression (i, j) observed reading of individual grid magnetic anomaly.

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