CN111259524B - A method for simulating sediment distribution in submarine hydrothermal areas based on topographic data - Google Patents

Abstract

The present invention discloses a method for simulating the distribution of sediments in a seafloor hydrothermal area based on topographic data, comprising the following steps: step 1: selecting a study area; step 2: collecting and rasterizing the topographic data of the study area; step 3: determining whether there is a depression basin in the study area, and if so, extracting the range of the depression basin; step 4: analyzing the topographic grid data of the study area to obtain the grid of the gravity transport direction of sediments; step 5: simulating and calculating the sediment collection amount grid of each grid; step 6: reclassifying and performing buffer zone analysis on the sediment collection amount in the study area to generate a sediment enrichment area; step 7: delineating the sediment distribution range in the study area. The method of the present invention makes full use of the seafloor topographic data information, effectively simulates the sediment distribution in the seafloor hydrothermal area, and conveniently and quickly obtains the sediment distribution range in the study area; it is suitable for the early stage of the investigation work in the study area, and has the advantages of fast speed, low cost and high efficiency.

Description

A method for simulating sediment distribution in submarine hydrothermal areas based on topographic data

Technical Field

The present invention relates to a method for simulating the distribution of sediments in a seafloor hydrothermal area based on topographic data, and in particular to a method for simulating the distribution of sediments around a seafloor hydrothermal area by using seafloor topographic data combined with information on the sedimentation rate of materials in a study area.

Background technique

The seabed is rich in mineral resources. Especially today when land resources are beginning to be gradually depleted, people have turned their attention to the vast ocean. The development and exploration of marine resources has become a hot spot of competition among countries around the world.

Since signing the world's first polymetallic sulfide exploration contract with the International Seabed Authority, my country has implemented a large number of ocean survey voyages, using remotely operated unmanned submersibles (ROVs), autonomous underwater robots (AUVs), manned submersibles (HOVs), gravity columns, anchoring equipment, TV grabs, seismic OBS and other marine survey equipment to carry out a large number of surveys and explorations in the hydrothermal areas of the mid-ocean ridge. However, due to work objectives or working conditions, the layout of many of these equipment is related to the distribution of sediments, such as gravity column equipment, OBS equipment, anchors, grabs, etc. For example, the layout of gravity column stations is divided into targeted station layout and exploratory station layout. Regardless of the method, they need to be laid out in sediment distribution areas; while OBS needs to have a good coupling relationship with the seabed, so it needs to be laid out in areas without sediment distribution. Therefore, in the voyage design stage, its workstation must be scientifically and reasonably designed. However, due to the difficulty and high cost of marine surveys, the types and amount of various geological data in the seabed area are often not as rich as those in land areas. Especially in sea areas with less preliminary work, voyage design and work plan layout are often carried out with less data, which requires us to use limited terrain data to simulate and analyze the distribution range of sediments in the seafloor hydrothermal area, and further provide reference for related work. After searching, there is currently no public technical method for this.

Summary of the invention

The purpose of the present invention is to provide a method for simulating the distribution of sediments in seafloor hydrothermal areas based on topographic data in order to address the deficiencies of the prior art, so as to provide support and reference for seafloor related surveys. Compared with traditional field surveys, this method can conveniently and quickly simulate the distribution range of sediments in seafloor hydrothermal areas, saving a lot of time and labor costs.

To achieve the above object, the present invention adopts the following technical solution: a method for simulating the distribution of sediments in a seafloor hydrothermal area based on topographic data, specifically a method for analyzing the sediment transport-enrichment process using seafloor topographic data, and then simulating the distribution range of sediments in a hydrothermal area, comprising the following steps:

Step 1: Select the study area;

Step 2: Collect topographic data of the study area and rasterize it;

Step 3: Fill the depressions in the terrain grid of the study area and determine whether there are sunken basins in the study area. If not, proceed directly to the next step. If yes, extract the scope of the sunken basins.

Step 4: Use the flow direction analysis tool to obtain the sediment gravity transport direction grid in the study area;

Step 5: Based on the sediment gravity transport direction grid obtained in step 4, the sediment collection grid of the study area is simulated and calculated using the flow analysis tool;

Step 6: Reclassify the sediment accumulation raster of the study area obtained in step 5, and perform buffer zone analysis based on the reclassification results to generate sediment enrichment areas;

Step 7: Comprehensively consider the scope of the depression basin and the sediment-rich area to delineate the sediment distribution range of the study area.

Furthermore, the rasterization method of the terrain data of the study area described in step 2 is specifically: using the original terrain XYZ data to create TIN, wherein the projection method selects Geographic-World-WGS 1984, and then using the TIN to Raster tool to generate the terrain raster data of the study area, wherein the interpolation method selects bilinear interpolation.

Furthermore, the method for judging the existence and extracting the range of the sunken basin in the study area described in step 3 is as follows: fill the depressions in the terrain grid of the study area using the ArcGIS depression filling tool, and then display the terrain grid data without depressions in discrete color mode. At this time, the sunken basin will be displayed as a monochrome area of a certain range. If there is an obvious monochrome area in the figure, it means that there is a sunken basin in the study area. The boundaries of these monochrome areas are extracted to obtain the range of the sunken basin in the study area; if there is no obvious monochrome area in the figure, it means that there is no sunken basin in the study area.

Furthermore, the method for obtaining the sediment gravity transport direction grid in step 4 is specifically: using the flow direction analysis tool of ArcGIS to analyze the terrain grid data after the depression is filled in step 3, and obtaining the sediment gravity transport direction grid of the study area. The result indicates the direction in which the sediment is transported at each grid in the study area under the action of the terrain.

Furthermore, the calculation method for the sediment accumulation grid simulation in step 5 is as follows: the sediment gravity transport direction grid obtained in step 4 is used as input data, and the sediment transportation-enrichment process is analyzed through the flow analysis tool of ArcGIS to obtain the sediment accumulation grid of the study area. The result can indicate the degree of sediment enrichment at each grid in the study area, and is the basis for simulating the sediment distribution.

Furthermore, in the simulation calculation process of the sediment accumulation grid in the study area in step 5, the sediment settling rate grid of the study area is added as the weight grid data, and different weight values are assigned to each grid in proportion according to the actual sediment settling rate at each grid.

Furthermore, when reclassifying the sediment accumulation grid of the study area as described in step 6, the classification index should follow the following principles:

(1) Determine the minimum threshold of the reclassification index based on the actual range of the sediment accumulation raster data, which can usually be 10%-30% of the maximum sediment accumulation;

(2) Assign a null value to the sediment collection grid that is less than the minimum threshold.

(3) The grids with a value greater than the minimum threshold are divided into n categories in equal proportion and assigned values of 1, 2, …, n in descending order according to the amount of sediment accumulation;

(4) The minimum threshold and number of categories can be adjusted appropriately according to the actual characteristics of the study area.

Furthermore, the buffer zone analysis method of the sediment accumulation reclassification result described in step 6 is specifically as follows: vectorizing the sediment accumulation raster after reclassification, and then generating n types of line features according to the reclassification values; using the buffer zone analysis tool to analyze them respectively, as the reclassification values increase, the corresponding buffer zone radius also increases; and using the obtained series of buffer zones as sediment enrichment areas.

Furthermore, the delineation of the sediment distribution range in step 7 should follow the following principles:

(1) The sediment distribution range should include all sediment-rich areas;

(2) In areas where sediment-rich areas are densely distributed, if the distance between two sediment-rich areas is smaller than the width of the sediment-rich area itself, they can be appropriately connected and the non-sediment-rich area in between can be uniformly defined as the sediment distribution range;

(3) If there is a depression basin in the study area, the depression basin is also defined as the sediment distribution range;

(4) The boundaries of the sediment distribution range should be defined around sediment-rich areas and depression basins.

Furthermore, in step 7, the end of the small-scale sediment-enriched area obtained by using the minimum buffer radius analysis can be discarded without being included in the sediment distribution range.

The method of the present invention has the following beneficial effects:

Compared with traditional field survey methods, it is more efficient and faster, saving a lot of time and cost;

The grids with different sediment accumulation amounts were classified and discussed, and different buffer radiuses were set to make the simulation results more reasonable and credible;

The sedimentation rate data of the study area are selected as the weight parameter for sediment accumulation simulation, and the simulation process has high reliability;

It can be applied at different scales, both to simulate sediment distribution over a larger area and to perform local analysis on an area of interest.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a flow chart of the implementation process of the present invention.

FIG. 2 is a diagram showing the range of the sunken basin extracted during the implementation of the present invention.

FIG. 3 is a diagram showing a sediment-rich area generated during the implementation of the present invention.

FIG. 4 is a diagram showing the sediment distribution range delineated during the implementation of the present invention.

Detailed ways

The following describes the implementation methods of the present invention in detail with reference to the accompanying drawings and through specific examples. Those skilled in the art can easily understand the implementation steps, effects and advantages of the present invention based on the contents of the specification. The present invention can be applied not only to hydrothermal areas, but also to other sediment-rich areas on the seabed. Technicians can make adjustments to various details according to different application scenarios without departing from the spirit of the present invention, such as sedimentation rate, minimum threshold and number of reclassifications, buffer zone radius, etc. It should be noted that any adjustment of details made by any person skilled in the art within the scope of the claims falls within the scope of protection of the present invention.

Referring to the schematic diagram of the process in FIG1 , the present invention provides a method for simulating sediment distribution in a seafloor hydrothermal area based on topographic data, comprising the following steps:

Step 1: Select the study area;

Step 2: Collect topographic data of the study area and rasterize it;

The following is one way to implement rasterization, but it is not limited to this: Use the original terrain XYZ data to create TIN, where the projection method is Geographic-World-WGS 1984, and then use the TIN to Raster tool to generate the terrain raster data of the study area, where the interpolation method is bilinear interpolation.

Step 3: Fill the depressions in the terrain grid of the study area and determine whether there are sunken basins in the study area. If not, proceed directly to the next step. If yes, extract the scope of the sunken basins.

The following is one implementation method for determining the existence and range of a sag basin, but is not limited to this:

Use ArcGIS's Depression Fill tool to fill depressions in the terrain raster of the study area, and then display the depression-free terrain raster data in discrete color mode. At this time, the sunken basin will be displayed as a monochrome area within a certain range. If there is an obvious monochrome area in the figure, it means that there is a sunken basin in the study area. Specifically, the boundaries of the monochrome areas whose area exceeds 5‰ of the total area of the study area can be extracted to obtain the scope of the sunken basin in the study area; if there is no obvious monochrome area in the figure, it means that there is no sunken basin in the study area.

The range of the sunken basin extracted in this embodiment is shown in FIG2 .

Step 4: Use the flow direction analysis tool of ArcGIS to analyze the terrain raster data after the depression filling in step 3 to obtain the gravity transport direction raster of the sediment in the study area. The result indicates the direction of sediment transportation at each grid in the study area under the action of terrain.

Step 5: Based on the sediment gravity transport direction grid obtained in step 4, the flow analysis tool of ArcGIS is used to simulate and calculate the sediment collection grid of the study area;

The following is one way to obtain the sediment gravity transport direction grid, but it is not limited to this:

The sediment gravity transport direction grid obtained in step 4 is used as input data. The sediment transport-enrichment process is analyzed through the flow analysis tool of ArcGIS to obtain the sediment accumulation grid of the study area. This result can indicate the degree of sediment enrichment at each grid in the study area and is the basis for simulating sediment distribution.

The default weight value of all grids is 1. As a preference, in this step, the sediment settling rate grid of the study area can be added as the weight grid data, and different weight values can be assigned to each grid in proportion according to the actual sediment settling rate at each grid.

Step 6: Reclassify the sediment accumulation raster of the study area obtained in step 5, and perform buffer zone analysis based on the reclassification results to generate sediment enrichment areas;

The following are the principles that should be followed in formulating classification indicators during reclassification, but are not limited to these:

(1) Determine the minimum threshold of the reclassification index based on the actual range of the sediment accumulation raster data, which can usually be 10%-30% of the maximum sediment accumulation;

(2) Assign a null value to the sediment collection grid that is less than the minimum threshold.

(3) The grids with a value greater than the minimum threshold are divided into n categories in equal proportion. In this embodiment, n is 3, and the values are assigned in descending order of the sediment accumulation amount: 1, 2, and 3;

(4) The minimum threshold and number of categories can be adjusted appropriately according to the actual characteristics of the study area.

The following is a method for implementing buffer zone analysis based on the reclassification results, but it is not limited to this:

The reclassified sediment accumulation raster is vectorized, and n types of line features are generated according to the reclassification values. The buffer analysis tool is used to analyze them respectively. In this embodiment, three types of line features are generated. For the reclassification values 1, 2, and 3, the buffer radius is set to 400m, 700m, and 1000m respectively; the obtained series of buffers are used as sediment enrichment areas.

The sediment-rich area generated in this embodiment is shown in FIG3 .

Step 7: Comprehensively consider the scope of the depression basin and the sediment-rich area to delineate the sediment distribution range of the study area.

The following are the principles that should be followed in delineating the sediment distribution range, but are not limited to these:

(1) The sediment distribution range should include all sediment-rich areas;

(2) In areas where sediment-rich areas are densely distributed, if the distance between two sediment-rich areas is smaller than the width of the sediment-rich area itself, they can be appropriately connected and the non-sediment-rich area in between can be uniformly defined as the sediment distribution range;

(3) If there is a depression basin in the study area, the depression basin extracted in step 3 is also delineated as the sediment distribution range;

(4) The boundaries of the sediment distribution range should be delineated around sediment-rich areas and depression basins;

(5) For the small-scale sediment-rich area obtained by using the minimum buffer radius analysis in step 7, its end can be discarded and does not need to be included in the sediment distribution range.

The sediment distribution range defined in this embodiment is shown in FIG4 .

The above embodiments are only used to illustrate the technical solutions of the present invention. The technical personnel can make adjustments to the details according to different application scenarios without departing from the spirit of the present invention. The scope of protection of the present invention shall be subject to the scope of the claims.

Claims (1)

1. A submarine hydrothermal area sediment distribution simulation method based on topographic data is characterized by comprising the following steps:

step 1: selecting a study area;

step 2: collecting and rasterizing topographic data of a research area; the method comprises the following steps: creating TIN by using original topography XYZ data, wherein a projection mode selects a Geographic-World-WGS1984, and then generating topography raster data of a research area by using a TIN rotary raster tool, wherein an interpolation mode selects bilinear interpolation;

step 3: filling the depressions of the land grid of the research area, judging whether a concave basin exists in the research area, if not, directly entering the next step, and if so, extracting the range of the concave basin; the method for judging the existence of the concave basin in the research area and extracting the range comprises the following steps: filling depressions in a land grid of a research area by using a depression filling tool of an ArcGIS, displaying land grid data without depressions in a discrete color mode, displaying a concave basin as a single-color area in a certain range, if obvious single-color areas exist in the figure, meaning that the concave basin exists in the research area, and extracting boundaries of the single-color areas to obtain the range of the concave basin of the research area; if no obvious monochromatic area exists in the graph, the concave basin does not exist in the research area;

step 4: acquiring a sediment gravity conveying direction grid of the research area by using a flow direction analysis tool; the method comprises the following steps: analyzing the topographic raster data filled in the depressions in the step 3 by using a flow direction analysis tool of the ArcGIS to obtain a gravity carrying direction grid of the sediment in the research area, wherein the gravity carrying direction grid is used for indicating the carrying direction of the sediment at each grid in the research area under the action of topography;

step 5: based on the sediment gravity conveying direction grids obtained in the step 4, simulating and calculating sediment collection grids in the research area through a flow analysis tool; the sediment collection grid simulation calculation method specifically comprises the following steps: analyzing the sediment carrying-enriching process by using the sediment gravity carrying direction grids obtained in the step 4 as input data through a flow analysis tool of the ArcGIS to obtain sediment collecting quantity grids of a research area, wherein the sediment collecting quantity grids are used for indicating the sediment enriching degree at each grid of the research area and are the basis for simulating sediment distribution; in the calculation process, a sediment sedimentation rate grid of a research area is added as weight grid data, and each grid is given different weight values according to the actual sediment sedimentation rate at each grid in proportion;

step 6: reclassifying the sediment collection grids of the research area obtained in the step 5, and respectively carrying out buffer area analysis according to reclassifying results to generate sediment enrichment areas; the sediment collection amount reclassification result buffer area analysis method specifically comprises the following steps: vectorizing the sediment collection grid subjected to reclassification, and correspondingly generating n types of line elements according to reclassification assignment; analyzing the buffer area by using a buffer area analysis tool respectively, and increasing the radius of the corresponding buffer area along with the increase of reclassification assignment; taking the obtained series of buffer areas as sediment enrichment areas;

when the sediment collection grid of the research area is reclassified in the step 6, the classification index formulation should follow the following principle:

(1) Determining a minimum threshold of a reclassification index according to the actual range of deposit aggregate raster data, and taking 10% -30% of the maximum value of deposit aggregate;

(2) Assigning a sediment collection grid less than a minimum threshold value to a null value;

(3) Dividing the equal proportion of the grids larger than the minimum threshold into n classes, and sequentially assigning 1,2, … and n according to the collection amount of the sediments from small to large;

(4) The minimum threshold and the classification number can be properly adjusted according to the actual characteristics of the research area;

step 7: integrating the concave basin range and the sediment enrichment area, and delineating the sediment distribution range of the research area; the deposit distribution range should follow the following principle:

(1) All sediment-enriched zones should be included in the sediment distribution range;

(2) In the densely distributed areas of the sediment enrichment areas, if the distance between the two sediment enrichment areas is smaller than the width of the sediment enrichment areas, the sediment enrichment areas can be properly connected, and the non-sediment enrichment areas between the sediment enrichment areas are uniformly defined as sediment distribution ranges;

(3) If a concave basin exists in the research area, the concave basin is also defined as a sediment distribution range;

(4) The sediment distribution range boundary should be delineated around the sediment enrichment zone and the recessed basin;

for small-scale sediment enrichment zones obtained using minimum buffer radius analysis, their ends can be discarded without circling around the sediment distribution range.