Name
Moho Discontinuity Estimation under the Ulleung Basin using Gravity Inversion
Description
The depth to Moho is estimated under the Ulleung Basin (UB) using free air gravity anomalies. This basin is one of three major basins in the East Sea. Based on the seismic refraction data, whilst this basin has the structure of an oceanic crust, it is twice as thick as a normal oceanic crust. The Moho discontinuity estimations help to understand the crustal structure of this basin. The gravitational effects of bathymetry and sediments are reduced off the gravity data utilizing a forward gravity model considering a two-layer model. The free air gravity anomalies, XGM2016 model data on a 0.1 by 0.1 degrees grid, are obtained from ICGEM. The bathymetry model is extracted from a 1 arc-minute terrain model from NOAA. A seismic stratigraphy of the deep Ulleung Basin in the East Sea from Lee et al., 2001 is used to extract a sedimentary layer map by adding bathymetry to isopach. An assembly of rectangular prisms with varied depths is considered over the study area in our forward model. A nonlinear 3-D inversion on reduced gravity data is used to estimate Moho discontinuity. This method utilizes the Levenberg-Marquardt technique to iteratively update the depth to the boundary until a solution that satisfies the gravity measurements with a reasonable misfit is estimated. The estimated depth to Moho under UB varies from 14 to 28 km. While the deeper Moho values are estimated along the basin edges, in central areas of the UB the Moho estimations are between 16 to 20 km.