Deformation of erosive and accretive forearcs during subduction of migrating and non‐migrating aseismic ridges: Results from 3‐D finite element models and application to the Central American, Peruvian, and Ryukyu margins

Abstract

Subduction of aseismic oceanic ridges causes considerable uplift and deformation of the upper plate and may lead, for example, to the indentation of the forearc, the formation of marine terraces, or distinct fault patterns in the upper plate. Depending on the orientation of the ridge relative to the plate convergence direction, the ridge may either be stationary or migrate along the margin. Here we use three-dimensional numerical models to investigate the tectonic evolution of forearcs affected by ridge subduction. In different experiments, we distinguish between migrating/non-migrating ridges and accretive/erosive margins, respectively. Our results reveal that displacement and strain fields above migrating and non-migrating ridges are asymmetric with respect to the ridge axis unless both ridge and plate convergence direction are perpendicular to the trench. As the asymmetric deformation pattern shifts along the margin through time, uplift caused by the underthrusting ridge is followed by subsidence when the ridge crest passed by, and regions initially experiencing shortening may subsequently undergo extension and vice versa. If the forearc comprises an accretionary prism, the ridge-induced reentrant is larger than those in models with erosive forearcs and strain localizes in the frontal part of the wedge. Additional models with a setup adjusted to the Cocos and Gagua Ridges provide constraints on the onset of their subduction at the Central American and Ryukyu margins at~2 Ma and 1 Ma, respectively. Displacement and strain fields from a model for the Nazca Ridge collision zone show good agreement with geological data from marine terraces and Quaternary faulting.

From incipient island arc to doubly‐vergent orogen: A review of geodynamic models and sedimentary basin‐fills of southern Central America

“…De Boer et al, ; H. Krawinkel et al, ) relative to the Sandino basin, leading to a differential uplift and subsidence of the outerarc and forearc area in northern Costa Rica. This uplift and subsidence pattern can be best explained by the subduction of a northeast–southwest trending aseismic ridge, which is consistent with modeling results of Zeumann and Hampel ().…”

“…Repeated phases of uplift and subsidence in the forearc area since the Paleocene can be best explained by changes in the subduction parameters. Uplift followed by subsidence can be a consequence of the subduction of aseismic ridges (Sak, Fisher, & Gardner, ; Zeumann & Hampel, ) or the accretion of oceanic plateaus (Walther et al, ) and oceanic islands (Buchs et al, ; H. Krawinkel et al, ).…”

“…E. Silver, et al, ) has a strong influence on vertical movements of the upper plate (Sak et al, ). Crust with a rough morphology, entering the subduction zone initially caused uplift of the upper plate, followed by increased subsidence due to enhanced subduction erosion (Sak et al, ; Zeumann & Hampel, ). This could explain the complex young subsidence and uplift history that is documented from the outerarc and the inner forearc at Osa.…”

Origin and dynamics of depositionary subduction margins

“…This event correlates with the onset of subduction of the Cocos Ridge [ MacMillan et al ., ], which occurred immediately after the subduction of the Panama Fracture Zone system in this region. The uplift/subsidence evolution in Figure b agrees well with models of spatial distribution of ridge‐induced vertical displacement [ Zeumann and Hampel , ], where the maximum uplift value is located above the ridge tip and near the trench separated by an area of relative subsidence. Here, though, subsidence cannot be used to estimate upper plate thinning because of the subducting topography and the subsequent uplift.…”

Structure of the Collision Zone Between the Nazca Ridge and the Peruvian Convergent Margin: Geodynamic and Seismotectonic Implications

“…Hot spot tracks and oceanic plateaus entering a subduction zone modify the structure of the forearc system and influence dramatically the coupling degree across the subduction interface affecting both interplate and intraplate seismicity (e.g., Bilek, ; Contreras‐Reyes & Carrizo, ; Wang & Bilek, ). In addition, the collision of oceanic high features with a convergent margin enhances subduction erosion (e.g., Balance et al, ; Hampel et al, ; Ranero & von Huene, ) and usually modifies locally the morphology of the upper plate causing uplift in the frontal part of the collision zone followed by subsidence as the aftermath of seamount subduction (e.g., Dominguez et al, ; Zeumann & Hampel, ).…”