변중무 교수

Due to the rapid development and spread of deep learning technologies, potential applications of artificial intelligence technology in the field of geophysical inversion are being explored. In this study, we applied a deep neural network (DNN) to reconstruct one-dimensional electrical resistivity structures from airborne electromagnetic (AEM) data for varying sensor heights. We used numerical models and their simulated AEM responses to train the DNN to be an inversion operator, and determined th

Abstract An acoustic logging tool in inclined or horizontal boreholes may be placed apart from the center and produce additional complicated wavefields. We investigate the effects of an off-centered tool on monopole, dipole, and quadrupole logs due to off-centering of the tool. In recent logging tools, monopole, dipole, and quadrupole logs can be obtained by adding or subtracting responses at four monopole (pressure) receiver arrays at right angles. We examine the responses of the four monopole

We present a series of processes for understanding and analysing controlled-source electromagnetic (CSEM) responses for a conductive and permeable earth. To realize the CSEM response, a new 3-D CSEM forward modelling algorithm based on an edge finite element method for both electrically conductive and magnetically permeable heterogeneities is developed. The algorithm shows highly accurate results in validation tests against a semi-analytic solution for stratified earth and an integral form of th

A R Y Full-waveform inversion (FWI) provides a high-resolution velocity model, but carries a high computational cost. Additionally, modern seismic acquisition, with dense sources and receivers, generates massive data, resulting in an even greater computational cost. To reduce the computational burden of FWI, we have developed an FWI algorithm using plane-wave data. Using this approach, plane-wave gathers transformed from shot gathers are used as input data in inversion. Because the number of pla

Abstract Time-lapse crosswell seismic provides an efficient way to monitor the migration of a CO2 plume or its leakage after CO2 injection into a geologic formation. Recently, crosswell seismic has become a powerful tool for monitoring underground variations, using the concept of a virtual source, with virtual sources positioned at the receivers installed in the well and thus the positions of sources and receivers can be invariant during monitoring. However, time-lapse crosswell seismic using ve

Typically, seismic data are sparsely and irregularly sampled due to limitations in the survey environment and these cause problems for key seismic processing steps such as surface-related multiple elimination or wave-equation-based migration. Various interpolation techniques have been developed to alleviate the problems caused by sparse and irregular sampling. Among many interpolation techniques, matching pursuit interpolation is a robust tool to interpolate the regularly sampled data with large

Abstract Vertical seismic profiling/common depth point (VSP-CDP) mapping is often preferred to crosswell migration when imaging crosswell seismic reflection data. The principal advantage of VSP-CDP mapping is that it can be configured as a one-to-one operation between data in the acquisition domain and data in the image domain and therefore does not smear coherent noise such as tube waves, guided waves, and converted waves as crosswell migration could. However, unlike crosswell migration, VSP-CD

Microseismic monitoring provides important information on the locations and moment tensors of microseismic events, and this information can be used to understand the behaviour of the fractures more completely. Characterisations of fractures are used to investigate flow paths and for noninvasive investigation of shale gas sites, geothermal developments, and radioactive waste storage/disposal sites. The locations of microseismic events can be used to estimate the geometry and distribution of fract