期刊名称：IOP Conference Series: Earth and Environmental Science
印刷版ISSN：1755-1307
电子版ISSN：1755-1315
出版年度：2008
卷号：2
出版社：IOP Publishing
摘要：The fastest modern-day tectonic block rotations on Earth (up to 9 degrees/Myr)
occur in the forearcs of convergent plate margins where a transition from
collision of a bathymetric high to subduction of normal oceanic crust occurs.
GPS techniques have enabled accurate documentation of the kinematics of these
rotations, leading us to develop a conceptual model where the change from
collision to subduction exerts a torque on microplates within the plate boundary
zone, causing them to spin rapidly about an axis at the collision point. We have
investigated geophysical and geological data from several active plate
boundaries (from the western Pacific and Mediterranean regions) to document a
compelling spatial and temporal relationship between the transition from
collision to subduction, plate boundary curvature, and rapid tectonic block
rotations. In some cases, these microplate rotations can initiate back-arc
rifting. We also present numerical modelling results supporting our conceptual
model for block rotations at collision/subduction transition. Our results
suggest that the rate of microplate rotation depends on the incoming indentor
velocity, and can be greatly enhanced by: (1) extensional stresses acting at the
subduction interface (possibly due to slab roll back), and (2) a low-viscosity
back-arc. Where viscosity of the back-arc is low, forearc microplate rotation
dominates. In contrast, tectonic escape of strike-slip fault-bounded microplates
is predicted in areas where the back-arc viscosity is high. Previous workers
have suggested that the kinematics of the Anatolian block and back-arc rifting
in the Aegean are influenced by some combination of forces associated with
Arabia/Eurasia collision, and/or subduction (including slab rollback) at the
Hellenic trench. Based on previous work from active western Pacific arcs, we
propose that the collision of two separate indentors (Arabian promontory in the
east, Apulian platform in the west), is a fundamental tectonic mechanism for
large-scale anticlockwise tectonic rotation of Anatolia and the opposing
clockwise rotation of western Greece documented from paleomagnetic studies. The
recognition of several global analogues for Mediterranean active tectonics may
lead to new insights into the dominant forces behind tectonic processes there.
