Efficient modeling of the gravity anomaly caused by a sedimentary basin with lateral variable density contrast and its application in basement relief estimation
Feng Xu-Liang♦1,2, Liu Sheng-Rong 3, and Shen Hong-Yan 1,2
1. School of Earth Sciences and Engineering, Xi’an Shiyou University, Xi’an 710065, China.
2. Shaanxi Key Laboratory of Petroleum Accumulation Geology, Xi’an Shiyou University, Xi’an 710065, China.
3. Xi’an Center of Geological Survey (Northwest China Center for Geoscience Innovation), Xi’an 710054, China.
Abstract：
The forward calculation of gravity anomalies is a non-negligible aspect contributing to the time consumption of the entire process of basement relief estimation. In this study, we develop a fast hybrid computing scheme to compute the gravity anomaly of a basement. We use the vertical prism source equation in a given region R centered at a certain gravity observation point and the vertical line source equation outside R to derive the gravity anomaly. We observe that the computation with the vertical line source equation is much faster than that of the vertical prism source equation, but the former is slightly inaccurate. Therefore,our method is highly efficient and able to avoid the errors caused by the low accuracy of the vertical line source equation near the observation point. We then derive the general principle of choosing the size of R via a series of prism model tests. Our tests on the gravity anomaly over the Los Angeles Basin confirm the correctness of our proposed forward strategy. We modify Bott’s method with an accelerating factor to expedite the inversion procedure and presume that the density contrast between the sediments and the basement in a sedimentary basin varies laterally and can be obtained using the equivalent equation. Synthetic data and real data applications in the Weihe Basin illustrate that our proposed method can accurately and effi ciently estimate the basement relief of sedimentary basins.
. Efficient modeling of the gravity anomaly caused by a sedimentary basin with lateral variable density contrast and its application in basement relief estimation[J]. APPLIED GEOPHYSICS, 2021, 18(2): 145-158.
2021, Vol. 18 
