An Active Seismic Zone in Intraplate West Iberia Inferred From High-Resolution Geophysical Data

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11320%2F18%3A10384784" target="_blank" >RIV/00216208:11320/18:10384784 - isvavai.cz</a>

Result on the web

<a href="https://doi.org/10.1002/2017JB015114" target="_blank" >https://doi.org/10.1002/2017JB015114</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1002/2017JB015114" target="_blank" >10.1002/2017JB015114</a>

Result language

angličtina

Original language name

An Active Seismic Zone in Intraplate West Iberia Inferred From High-Resolution Geophysical Data

Original language description

Intraplate Iberia is a region of slow lithopsheric deformation (&lt;1mm/yr) with significant historical earthquake activity. Recent high-quality instrumental data have shown that small-magnitude earthquakes collapse along clusters and lineaments, which however do not bear a clear relationship to geologically mapped active structures. In this article, we investigate the controls of these earthquake clusters. In particular, we study two of the identified clustersthe Arraiolos and the Evora seismic zones (ASZ and ESZ), located in the Western Ossa Morena Zone, southwest Iberia. The ASZ marks a sharp boundary between a seismically active region to its south and a more quiet region to its north. We revise historical earthquakes in order to clarify whether earthquake activity in the region is persistent. We use data from a local network to compute accurate epicenters, focal depth, focal mechanisms, and spatiotemporal clustering, thus characterizing ongoing small-scale fracturing. Finally, we analyze complementary data sets, including tomographic models, Global Navigation Satellite Systems data, magnetic anomalies, and gravity anomalies, in order to discuss the factors that control seismogenesis in the two seismic zones. Consistency between earthquake locations, focal mechanisms and Global Navigation Satellite Systems data suggests that the ASZ is an active right-lateral shear zone, which divides two blocks within the Western Ossa Morena Zone. The ESZ seems to localize microseismicity due to its granitic lithology. These results suggest that high-resolution geophysical data have the potential to reveal blocks with different seismogenic and rheological behaviors, which may be used to improve our understanding of fault systems and the assessment of earthquake hazard in slowly deforming regions. Plain Language Summary Mainland Portugal is a region of slow lithospheric deformation. This means that changes in Earth&apos;s outmost layerthe lithosphereoccur at very low rates (&lt;1mm/yr). In such environments, faults producing earthquakes are not easy to identify at the Earth&apos;s surface, both because their evidence can be gradually erased by wind and water or simply because they do not reach the surface. Recent studies have shown that small earthquakes in mainland Portugal group together delineating seismically more active regions. In this article we focus in two particular groups of earthquakesthe Arraiolos and the Evora seismic zones (ASZ and ESZ) and we investigate why they occur in these particular locations. We obtain precise maps of earthquake epicenters. When possible, we also analyze the direction of slip during the earthquake and the orientation of the fracture on which it occurred. We compare our results with other data sets, such as images of the Earth&apos;s interior, that could give hints about the constitution of crust beneath the ASZ and the ESZ. Earthquakes epicenters show fault sections at depth in the ASZ. These faults separate two crustal blocks with distinct material properties. In the ESZ earthquakes are associated to contrasts in crustal materials.

Czech name

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Czech description

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Type

J_imp - Article in a specialist periodical, which is included in the Web of Science database

CEP classification

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OECD FORD branch

10500 - Earth and related environmental sciences

Project

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Continuities

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Publication year

2018

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Name of the periodical

Journal of Geophysical Research: Solid Earth

ISSN

2169-9313

e-ISSN

—

Volume of the periodical

123

Issue of the periodical within the volume

4

Country of publishing house

US - UNITED STATES

Number of pages

23

Pages from-to

2885-2907

UT code for WoS article

000434133700021

EID of the result in the Scopus database

2-s2.0-85045396890