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

authored by

Stefanie Zeumann, Andrea Hampel

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 ~2Ma and 1Ma, 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.

Organisation(s)

Institute of Geology

Type

Article

Journal

TECTONICS

Volume

34

Pages

1769-1791

No. of pages

23

ISSN

0278-7407

Publication date

01.09.2015

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Geophysics, Geochemistry and Petrology

Sustainable Development Goals

SDG 14 - Life Below Water

Electronic version(s)

https://doi.org/10.1002/2015TC003867 (Access: Unknown)