Fig. 1

Schematic diagram of seismic wave propagation The red parallel lines in the figure represent the strata; The red line represents the path of the reflected wave; The green curve represents the path of the rotating wave; The blue solid line represents the incident path of refracted waves; The blue dashed line represents the exit path of refracted waves. S is the excitation point; R1~R5 are receiving points"

Fig. 2

Workflow of full waveform inversion"

Fig. 3

Workflow of traveltime tomography"

Fig. 4

FWI and traveltime tomography combined for velocity modeling"

Tab. 1

Parameters of seismic data acquisition in Weixi"

Fig. 5

Raypath with an offset of 6000 m"

Fig. 6

Frequency analysis of input shot gather data. (a) raw data; (b) frequency band of 0.5~2 Hz; (c) frequency band of 0.5~4 Hz; (d) frequency band of 0.5~6 Hz; (e) frequency band of 0.5~8 Hz; (f) frequency band of 0.5~10 Hz"

Fig. 7

The observed and synthetic data blending show. (a) The synthetic (gray and white) is shown at the bottom and observed (red and blue) data is shown at the top; (b) The observed (gray and white) is shown at the bottom and synthetic (red and blue) data is shown at the top"

Fig. 8

Velocity modeling comparison. (a) Reflection traveltime tomography modeling; (b) FWI and reflection traveltime tomography combined modeling"

Fig. 9

Pre-stack depth migration comparison. (a) Tomography modeling; (b) FWI combined with tomography modeling. The blue circle area indicates small faults and internal structures of complex fault blocks; the yellow arrow indicates the wave group reflection characteristics of the target layer; The red dashed line indicates the fault"

Fig. 10

Application scope of this velocity modeling. (a) The stack data obtained by using the migrated tomography velocitymodeling results; (b) The new stack data obtained using the migrated FWI+ tomography velocity modeling results; (c) T32 depthmap after interpretation of the old stack data; (d) T32 depth map after interpretation of the new stack data. The bold black arrow infigure c indicates that figure a is a seismic profile passing through that location; the thick red solid line indicates a fractured upperplate; the thin red solid line represents the fractured lower plate; the red square represents the marking of a broken upper plate;yellow blocks represent explanatory blocks. the bold black arrow in figure d indicates that figure b is a seismic profile passingthrough that location; the thick red solid line indicates a fractured upper plate; the thin red solid line represents the fractured lowerplate; the red square represents the marking of a broken upper plate; yellow blocks represent explanatory blocks"