Publication Date:
2021-09-03
Description:
The Iberian Peninsula and the Maghreb experience moderate earthquake activity and oblique, ∼ NW–SE convergence between
Africa and Eurasia at a rate of ∼ 5 mm/yr. Coeval extension in the Alboran Basin and a N35°E trending band of active, left-lateral
shear deformation in the Alboran–Betic region are not straightforward to understand in the context of regional shortening, and
evidence complexity of deformation at the plate contact. We estimate 86 seismic moment tensors (MW 3.3 to 6.9) from time domain
inversion of near-regional waveforms in an intermediate period band. Those and previous moment tensors are used to describe
regional faulting style and calculate average stress tensors. The solutions associated to the Trans-Alboran shear zone show
predominantly strike-slip faulting, and indicate a clockwise rotation of the largest principal stress orientation compared to the
regional convergence direction (σ1 at N350°E). At the N-Algerian and SW-Iberian margins, reverse faulting solutions dominate,
corresponding to N350°E and N310°E compression, respectively. Over most of the Betic range and intraplate Iberia, we observe
predominately normal faulting, and WSW–ENE extension (σ3 at N240°E). From GPS observations we estimate that more than
3 mm/yr of African (Nubian)–Eurasian plate convergence are currently accommodated at the N-Algerian margin, ∼ 2 mm/yr in the
Moroccan Atlas, and ∼ 2 mm/yr at the SW-Iberian margin. 2 mm/yr is a reasonable estimate for convergence within the Alboran
region, while Alboran extension can be quantified as ∼ 2.5 mm/yr along the stretching direction (N240°E). Superposition of both
motions explains the observed left-lateral transtensional regime in the Trans-Alboran shear zone. Two potential driving
mechanisms of differential motion of the Alboran–Betic–Gibraltar domain may coexist in the region: a secondary stress source
other than plate convergence, related to regional-scale dynamic processes in the upper mantle of the Alboran region, as well as drag
from the continental-scale motion of the Nubian plate along the southern limit of the region. In the Atlantic Ocean, the ∼ 3.5 mm/
yr, westward motion of the Gibraltar Arc relative to intraplate Iberia can be accommodated at the transpressive SW-Iberian margin,
while available GPS observations do not support an active subduction process in this area.
Description:
Published
Description:
295-317
Description:
JCR Journal
Description:
reserved
Keywords:
GPS
;
Kinematics
;
04. Solid Earth::04.02. Exploration geophysics::04.02.06. Seismic methods
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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