National Gravity Compilation 2019 DGIR 0.5VD image

Gravity data measure small changes in gravity due to changes in the density of rocks beneath the Earth's surface. The data collected are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose. This National Gravity Compilation 2019 DGIR 0.5VD image is produced from the 2019 Australian National Gravity Grids A series. These gravity data were acquired under the project No. 202008. The grid represented in this image has a cell size of 0.00417 degrees (approximately 435m). The %%MV_DATASETS/SURVEY_NAME% are derived from ground observations stored in the Australian National Gravity Database (ANGD) as at September 2019, supplemented by offshore data sourced from v28.1 of the Global Gravity grid developed using data from the Scripps Institution of Oceanography, the National Oceanic and Atmospheric Administration (NOAA), and National Geospatial-Intelligence Agency (NGA) at Scripps Institution of Oceanography, University of California San Diego. Out of the approximately 1.8 million gravity observations, nearly 1.4 million gravity stations in the ANGD together with marine data were used to generate this grid. The ground gravity data used in this grid has been acquired by the Commonwealth, State and Territory Governments, the mining and exploration industry, universities and research organisations from the 1940's to the present day. Station spacing for ground observations varies from approximately 11 km down to less than 1 km, with major parts of the continent having station spacing between 2.5 and 7 km. The grid shows the half vertical derivative of the de-trended global isostatic residual anomalies (A series) over Australia and its continental margins. The original DGIR was obtained by subtracting 3 quantities (i.e., the near-field isostatic correction, the far-field isostatic correction, and a first order trend correction) from Complete Bouguer Anomaly data (CBA) of the 2019 Australian National Gravity Grids A series. A half vertical derivative was calculated by applying a fast Fourier transform (FFT) process to the DGIR grid of the 2019 Australian National Gravity Grids to produce the grid represented in this image.

重力数据用于观测地表下方岩石密度变化所引发的微小重力场变化。采集得到的重力数据将通过标准化流程进行处理，以确保记录的响应仅源于地下岩石的影响。经处理后得到的数据集可用于解译，以揭示地下地质结构。处理完成的数据将由GA地球物理学家开展质量核查，确保GA发布的最终数据符合使用需求。本2019年国家重力编目DGIR 0.5VD图像，源自2019年澳大利亚国家重力网格A系列。本次所用重力数据采集自项目编号202008的相关工作。本图像展示的网格单元尺寸为0.00417度（约435米）。本数据集（%%MV_DATASETS/SURVEY_NAME%）源自截至2019年9月存储于澳大利亚国家重力数据库（Australian National Gravity Database, ANGD）的地面观测数据，并补充了全球重力网格v28.1版的海洋数据；该全球重力网格基于加利福尼亚大学圣迭戈分校斯克里普斯海洋研究所、美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration, NOAA）以及美国国家地理空间情报局（National Geospatial-Intelligence Agency, NGA）的数据开发而成。在约180万条重力观测数据中，ANGD内近140万个重力测点与海洋数据一同被用于生成本次网格。本次网格所用的地面重力数据，采集自1940年代至今的联邦、州及领地政府、矿业与勘探行业、高校及科研机构。地面观测的测点间距范围约为11千米至不足1千米，澳大利亚大陆大部分区域的测点间距介于2.5千米至7千米之间。本网格展示了澳大利亚及其大陆边缘区域去趋势后的全球均衡剩余异常（A系列）的半垂直导数。原始DGIR数据通过从2019年澳大利亚国家重力网格A系列的完整布格异常（Complete Bouguer Anomaly, CBA）数据中减去三项校正量（即近场均衡校正、远场均衡校正以及一阶趋势校正）得到。通过对2019年澳大利亚国家重力网格的DGIR网格应用快速傅里叶变换（fast Fourier transform, FFT）流程计算半垂直导数，最终生成本图像展示的网格。