Fig.1 Geotectonic location (A), tectonic environment (A, after [34]) and tectonic zoning map (B, modified after [35]) of the Sichuan Basin

Fig.2 Characteristics of sedimentary strata, regional tectonic movement and environmental evolution of stress field in the Sichuan Basin. Modified from [40].

Fig.3 High-resolution coherence attribute slices through interfaces T 1q (A), TS (C) and TP2 (E) in the study area and interpretation of the corresponding coherence maps showing the distributions of the fault arrays (B, D, F)

Fig.4 Comparison of interpreted (left) and uninterpreted (right) seismic sections a-c normal to the southern segment of No.15 basement strike-slip fault zone. Symbols (☉) and ($\otimes$) respectively represent the forward and backward movement directions (relative to the reader) of the fault blocks on either sides of the strike-slip fault

Fig.5 Comparison between interpreted (bottom penal) and uninterpreted (top penal) seismic sections 1-3 respectively normal to basement strike-slip fault zones NE-F2, NE-F3 and NE-F4

Fig.6 Interpreted seismic sections showing abrupt stratum-thickness changes on either sides of the NE-trending NE-F2 (A) or the NW-trending No.15 (B) basement strike-slip fault zones in the study area

Fig.7 Photos showing important structural features on the Erya outcrop profiles for the identification of basement strike-slip faults in the Huaying Mountain area

Fig.8 Zonal plane distribution (A) and fault offset on horizontal time slice (B) of No.15 fault zone in Fuling area

Fig.9 Grid comparison of interpreted seismic sections of mater-fault segments (A-D) of No.15 fault zone with “ribbon-like” strike-slip fault patterns

Fig.10 Sectional views of interfaces TS, TP1 and TP2 of master faults in No.15 fault zone with “ribbon-like” fault pattern

Fig.11 Grid comparison of seismic interpretation sections of “dolphin effect” of master fault in No.15 basement strike-slip fault zone in Fuling area

Fig.12 Sectional views of interfaces TS, TP1 and TP2 of master faults in No.15 fault zone with “dolphin-like” fault pattern

Fig.13 Characteristics of vertical displacements and their variation patterns used in the new method to determine strike-slip directions

Fig.14 Variation of vertical displacement of seismic-reflection profiles 1-22 along the strike of the southern segment of No.15 fault zone at interfaces TS, TP1, TP2

Fig.15 Variation of vertical displacement of seismic-reflection profiles 1-28 along the strike of the northern segment of No.15 fault zone at interfaces TS, TP1, TP2

Fig.16 Balanced geological profile of NW-SE seismic sections on either sides of No.15 fault zone in different deformation stages for calculating strike-slip directions in each stage

Fig.17 Comparisons of tectonic-activity intensity parameters between the two sides of No.15 fault zone in different geological periods for calculating strike-slip offset in each period

Fig.18 Comparison of stratum-thickness peak positions between surfaces TP1 and TP1m on either sides of No.15 fault zone for calculating strike-slip offset

Fig.19 Fault development stages revealed on seismic sections of No.15 (A) and NE-F2 (B) basement strike-slip fault zones in Fuling area

Fig.20 Relationship between formation/evolution of strike-slip fault zones and regional tectonic activity in Fuling area, eastern Sichuan Basin

Fig.21 Model for the formation and multi-stage tectonic evolution of No.15 basement strike-slip fault zone in Fuling area, eastern Sichuan Basin

Fig.22 Model for the formation and multi-stage tectonic evolution of NE-F2 basement strike-slip fault zone in Fuling area, eastern Sichuan Basin