(a) Plots of the stability fields for critical taper wedges, with the surface slope (α) and basal dip (β). Four cases are plotted with different basal and internal friction angles. φb = basal friction angle; φ = internal friction angle. Case 1: φb = 24.0◦ (dynamic friction angle of the glass microbeads) and φ = 35.5◦ (peak friction angle of the sand). Case 2: φb = 24.0◦ (dynamic friction angle of the microbeads) and φ = 30.8◦ (dynamic friction angle of the sand). Case 3: φb = 30.8◦ (dynamic friction angle of the sand) and φ = 35.5◦ (peak friction of the sand). Case 4: φb = φ = 30.8◦ (dynamic friction angle of the sand). Details of the frictional properties are listed in Table 1. (b) Enlarged view of (a) around β = 0. The shaded area bounded by case 1 (αφpeak = 7.5◦ ) and case 2 (αφdynamic = 9.6◦ ) is the compressional critical zone for this study. –4– manuscript submitted to Journal of Geophysical Research: Solid Earth

Figure S2. Sketch for the calculation of the



theoretical width and height of the wedge. –5–

–

6

–

Plots of the geometrical parameters for all models. (a

) 

Width.

(

b

) 

Height

. (

c

) S

lope.



Vertical



lines

in the

right column indicate shortening lengths of theoretical width and height and the critical zone of the slope are explained in Supporting Information S1 (Figure S2). onset of the sand mound subduction. Horizontal lines of αcase1, αcase2, and αcase3 in (c) show the critical slope angles for the cases 1–3 (Figure S1). Regions of the Figure S3. manuscript submitted to Journal of Geophysical Research: Solid Earth Figure S4. Final stacking patterns of all models. Numbered faults are deeply rooted forethrusts

. manuscript submitted to Journal of Geophysical Research: Solid Earth –7– –8– Normalized horizontal displacements in the top measurement zone (ûtop ; left column) and bottom measurement zone (ûbottom ; middle column), and the degree of intra-wedge coupling between the upper and lower parts of the wedge. Meshed areas in (c) and (d) show the traces of the subducting sand mound. thrusts in the top and bottom measurement zones, respectively. White arrows are major out-of-sequence thrusts. In the right column, ratios ûtop /ûbottom indicate Type 4 model (M10). Thick solid lines indicate the deformation front. Dotted lines (left column) and dashed lines (middle column) show the positions of active their ratio (ûtop /ûbottom ; right column) (see Figure 3 for the measured locations). (a) Type 1 model (M06). (b) Type 2 model (M04).

(

c) Type 3 model

(M

08).

(d)

Figure S5.

m

anuscript submitted to Journal of Geophysical Research: Solid Earth manuscript submitted to Journal of Geophysical Research: Solid Earth Figure S6. Normalized vertical displacement (v̂) for the type 1–4 models. (a) Type 1 model –9– (M08). (d) Type 4 model (M10). Thick solid (M06). (b) Type 2 model (M04). (c) Type 3 model lines are the deformation fronts. Meshed areas in (c) and (d) show the traces of the subducting manuscript submitted to Journal of Geophysical Research: Solid Earth Figure S7. Normalized maximum shear strain in the top measurement zone (ε̂max(top) ; left column) and bottom measurement zone (ε̂max(bottom) ; right column) for the type 1–4 models. (a) Type 1 model (M06). (b) Type 2 model (M04). (c) Type 3 model (M08). (d) Type 4 model (M10). Positive and negative values indicate the direction of the shear strain (i.e., forethrusts [outward-vergent faults] are positive and backthrusts [inward-vergent faults] are negative). Thick solid lines show the deformation fronts. Thin horizontal lines indicate the timing of formation of a new deeply rooted frontal forethrust. White arrows are major out-of-sequence thrusts. Meshed areas in (c) and (d) show the traces of the subducting sand mound. –10– –11– DIC images of the normalized horizontal (û, left column), vertical displacement (v̂, middle column), and maximum shear strain (ε̂max ) showing an accretion cycle in the Type 1 model (M06). Interpretations are shown in Figure 6a.

Figure S8. manuscript submitted to Journal of Geophysical Research: Solid Earth –12– DIC images of the normalized horizontal (û, left column) and vertical displacement (v̂, right column) showing an accretion cycle in the Type 2 model (M04). Interpretations are shown in Figure 6b. Figure S9. manuscript submitted to Journal of Geophysical Research: Solid Earth Figure S10. DIC images of the sand mound subduction for the Type 3 model. Interpretations are shown in Figure 8. manuscript submitted to Journal of Geophysical Research: Solid Earth –13– Figure S11. DIC images of the sand mound subduction for the Type 4 model. Interpretations are shown in Figure 8. manuscript submitted to Journal of Geophysical Research: Solid Earth –14– –15– Figure S12. (a) Shortening length required for the propagation of a new deeply rooted frontal forethrust versus the length of a new ramp. (b) Initial dip angles Results for the other models are shown in Figure S13. Dashed lines (φ) indicate the measured friction angles of the sand (φdynamic = 30.8◦ and φpeak = 35.5◦ ) and glass microbeads (φdynamic = 24.0◦ and φpeak = 26.6◦ ). of the forethrust δf(init) and backthrust δb. Thin gray solid and dotted lines are the effective slope angle α′ and the effective internal friction angle φ′, respectively.

manuscript submitted to Journal of Geophysical Research: Solid Earth –16– Figure S13.

(a)

Shortening

length

for

p

ropagation

of



a new deeply rooted forethrust. (b) Length of a new ramp. (c) Initial dip angles of backthrust δb when a frontal forethrust is nucleated. new frontal forethrust is nucleated. (d) Initial dip angles of a new frontal forethrust δf(init). (e) Dip angles of trailing previous frontal forethrust δf(final) when a new manuscript submitted to Journal of Geophysical Research: Solid Earth : Solid

Type 1a M06.mp4 Images of photos Type 1 (single and continuous model). Model 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 number is M06. Type 2a M02.mp4 Images of photos Type 2 (double and continuous model). Model number is M02. Type 2a M04.mp4 Images of photos Type 2 (double and continuous model). Model number is M04. Type 3a M08.mp4 Images of photos of Type 3 (single and discontinuous model). Model number is M11. Type 3a M11.mp4 Images of photos of Type 3 (single and discontinuous model). Model number is M11. Type 4a M09.mp4 Images of photos of Type 4 (double and discontinuous model). Model number is M09. Type 4a M10.mp4 Images of photos of Type 4 (double and discontinuous model). Model number is M10. Type 4a M15.mp4 Images of photos of Type 4 (double and discontinuous model). Model number is M15. DIC Type 1a M06.mp4 Images of results of DIC analysis of Type 1 (single and continuous model). Model number is M06. DIC Type 2a M04.mp4 Images of results of DIC analysis of Type 2 (double and continuous model). Model number is M04. DIC Type 3a M08.mp4 Images of results of DIC analysis of Type 3 (single and discontinuous model). Model number is M08. DIC Type 4a M10.mp4 Images of results of DIC analysis of Type 4 (double and continuous model). Model number is M10. Figure 01. Figure 02. Figure 03. Figure 04. Figure 05. Figure 06. Figure 07. Figure 08. Figure 09. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14.