An Improved Method to Moho Depth Recovery From Gravity Disturbance and Its Application in the South China Sea

Two hyperparameters, the mean Moho depth and the Moho density contrast, must be specified before the gravity inversion of Moho. Incorrect estimation will impact inversed Moho morphology. The purpose of this study is to present a new gravimetric Moho inversion method. The key improvement of the new method is to accurately estimate the Moho density contrast, based on a linear relationship between the depth of known points and gravity observations. The method is illustrated by a synthetic experiment where the estimated density contrast differs from the true value by only 0.0011 g/cm3 $\mathrm{g}/{\text{cm}}<^>{3}$, showing a 93% improvement compared to the initial estimate. The results of processing the noise data show that, our method's accuracy is minimally affected by noise, but is sensitive to the number of known points. Nevertheless, when using only 10 known points, there is still a 50% probability of obtaining a solution with a root mean square (RMS) less than 1 km. When the number of points is greater than 64, the effect of the uniformity of the point distribution is almost negligible. In the real case, we employed the proposed method to invert the South China Sea (SCS) Moho depth. The Moho model reveals that, there is a distinct zoning feature at Moho depth in the SCS, and the 13.5 km isodepth line indicates the continent-ocean boundary. Furthermore, the RMS of the difference between the gravimetric Moho model and the seismological data is 1.64 km, which is primarily attributed to the lateral variation of the density contrast.