Tectonics
Supporting Information for
Deformation of erosive and accretive forearcs during subduction of migrating
and non-migrating aseismic ridges: Results from 3D finite-element models and
application to the Central American, Peruvian and Ryukyu margins
Stefanie Zeumann and Andrea Hampel
Institut für Geologie, Leibniz Universität Hannover, Hannover, Germany
Contents of this file
Figures S1 to S4
Introduction
The Supporting Information includes four figures with the results from models with
variable angles between ridge, trench and plate convergence direction, with a
subduction radius of the oceanic plate of 300 km and with a plate convergence
velocity of 4.5 cm/a.
1
Figure S1. Displacement and strain fields (shown in top view for the central part of
the forearc wedge) obtained from experiments with a non-migrating ridge and an
erosive forearc. Ridge and plate convergence direction form an angle of 30° with the
margin ( = = 30°). Shown are for model times of 0.5, 1 and 1.5 Ma the vertical
displacement, the rate of vertical displacement (averaged over 100 ka), the total
horizontal displacement (shown color-coded and by black arrows in the region above
the ridge) and the total horizontal strain. Positive and negative strain values indicate
shortening and extension, respectively. The horizontal displacement and strain field
normal and parallel to the margin, respectively, are shown at 1.5 Ma of model time.
2
Thick white arrows indicate the plate convergence direction and dashed white lines
denote the ridge position underneath the forearc.
3
Figure S2. Displacement and strain fields (shown in top view for the central part of
the forearc wedge) from experiments with migrating ridges oriented oblique to an
erosive forearc (cf. Figure 1c). (a) Plate convergence direction is  = -60° and ridge is
oriented  = 60° relative to the margin. (b)  = -30° and  = 60°, (c)  = 30° and  =
60°, (d)  = -30° and  = 30°. Shown are at a model time of 1.5 Ma the vertical
displacement, the rate of vertical displacement, the total horizontal displacement
(color-coded and black arrows in the region above the ridge) and the total horizontal
strain. Positive and negative strain values indicate shortening and extension,
respectively. Thick white arrows indicate the plate convergence direction and
dashed white lines denote the ridge position underneath the forearc.
Figure S3: Displacement and strain fields (shown in top view for the central part of
the forearc wedge) obtained from experiments with a radius of the oceanic plate of
300 km and a non-migrating ridge normal to an erosive forearc ( =  = 90°). Shown
are for model times of 0.5, 1 and 1.5 Ma the vertical displacement, the rate of
vertical displacement (averaged over 100 ka), the total horizontal displacement
(shown color-coded and by black arrows in the region above the ridge) and the total
horizontal strain. Positive and negative strain values indicate shortening and
4
extension, respectively. Note that the total strain is derived from the largest absolute
value of the principal strains (i.e. a value of -0.01 implies that the minimum principal
strain at this point shows extension and has a larger absolute value than the
maximum principal strain; this strain measure therefore allows differentiating between
areas of net extension or shortening). The horizontal displacement and strain field
normal and parallel to the margin, respectively, are shown at 1.5 Ma of model time.
Except for the rate of vertical displacement, all results are shown relative to the
beginning of the model run (i.e. 0 Ma model time). Thick white arrows indicate the
plate convergence direction and dashed white lines denote the ridge position
underneath the forearc.
Figure S4: Displacement and strain fields (shown in top view for the central part of
the forearc wedge) obtained from an experiment with a non-migrating ridge
perpendicular to an erosive forearc ( =  = 90°) and a plate convergence velocity of
4.5 cm/a. Results are shown at 1, 2 and 3 Ma of model time, i.e. at time points when
the ridge has the same position underneath the forearc as in the respective
experiment with 9 cm/a (Figure 2a). Shown are the vertical displacement, the rate of
vertical displacement (averaged over 100 ka), the total horizontal displacement
5
(shown color-coded and by black arrows in the region above the ridge) and the total
horizontal strain. Positive and negative strain values indicate shortening and
extension, respectively. Note that the total strain is derived from the largest absolute
value of the principal strains (i.e. a value of -0.01 implies that the minimum principal
strain at this point shows extension and has a larger absolute value than the
maximum principal strain; this strain measure therefore allows differentiating between
areas of net extension or shortening). The horizontal displacement and strain field
normal and parallel to the margin, respectively, are shown at 1.5 Ma of model time.
Except for the rate of vertical displacement, all results are shown relative to the
beginning of the model run (i.e. 0 Ma model time).
6