Methods and Systems for Generating Angle Dependent Imaging Condition for Multi-Parameter Elastic Full Waveform Inversion

A computing system comprising:

• a memory configured to store instructions;
• and
• one or more processors coupled to the memory and configured to execute the instructions to cause the computing system to:
• (a) obtain recorded seismic data;
• (b) obtain a current subsurface model comprising elastic full-waveform inversion (FWI) parameters, wherein the elastic FWI parameters comprise one or more of a velocity of P-wave (VP), a velocity of S-wave (VS), or a density of the subsurface (ρ);
• (c) obtain a source elastic wavefield and a receiver elastic wavefield based on the current subsurface model and the recorded seismic data;
• (d) calculate a source-receiver angle between a first propagation direction of the source elastic wavefield and a second propagation direction of the receiver elastic wavefield;
• (e) determine a limited range of source-receiver angles for each of the elastic FWI parameters that minimizes coupling among the elastic FWI parameters;
• (f) obtain a scaled gradient direction of an elastic FWI objective function with respect to each of the elastic FWI parameters using the limited range of source-receiver angles for each of the elastic FWI parameters;
• (g) update the elastic FWI parameters based on the scaled gradient direction to obtain updated elastic FWI parameters;
• and
• (h) input the updated elastic FWI parameters into the current subsurface model to update the current subsurface model.

A computer program product comprising computer-executable instructions that are stored on a non-transitory computer-readable medium and that, when executed by one or more processors, cause a computing system to:

• (a) obtain recorded seismic data;
• (b) obtain a current subsurface model comprising elastic full-waveform inversion (FWI) parameters, wherein the elastic FWI parameters comprise a velocity of P-wave (VP), a velocity of S-wave (VS), and a density of the subsurface (ρ);
• (c) obtain a source elastic wavefield and a receiver elastic wavefield based on the current subsurface model and the recorded seismic data;
• (d) calculate a source-receiver angle between a first propagation direction of the source elastic wavefield and a second propagation direction of the receiver elastic wavefield;
• (e) determine a limited range of source-receiver angles for each of the elastic FWI parameters that minimizes coupling among the elastic FWI parameters;
• (f) obtain a scaled gradient direction of an elastic FWI objective function with respect to each of the elastic FWI parameters using the limited range of source-receiver angles for each of the elastic FWI parameters;
• (g) update the elastic FWI parameters based on the scaled gradient direction to obtain updated elastic FWI parameters;
• and
• (h) input the updated elastic FWI parameters into the current subsurface model to update the current subsurface model.