{"title":"Catalogue of source mechanisms and overview of present-day stress fields in the western region of the Africa–Eurasia plate boundary","authors":"F. Ousadou, Abdelhakim Ayadi, M. Bezzeghoud","doi":"10.3389/feart.2024.1366156","DOIUrl":null,"url":null,"abstract":"Complex deformation is observed along the plate boundary between the Africa and Eurasia plates, this complexity is highlighted by the faulting mechanism changing from normal faulting at the Mid-Atlantic Ridge to thrust and strike-slip faulting in the Ibero-Maghreb region (Iberia, Morocco, Algeria and Tunisia). The geodynamics of the study area shows the occurrence of NW‒SE convergence between the two plates, with anticlockwise rotation. An updated scheme of the pattern of the tectonic stress direction from the Azores Archipelago to the Tunisian Atlas is presented, along with the analysis of the principal stress axis orientations (Shmax = σ1, Shmin = σ3) from the inversion of fault plane solutions. We used a catalogue of 557 fault plane solutions with only main shocks without considering the related aftershock solutions for the period from 1931 to 2020. This study complements previous work limited to Algeria and eastern Morocco by inverting earthquake mechanisms of aftershock sequences of strong events that occurred in Al Hoceima (Morocco), El Asnam, Chenoua-Tipasa, Zemmouri and Constantine (Algeria). The present work includes the area from Tunisia to the Mid-Atlantic Ridge. The inversion considers only the earthquake mechanisms of events 4.0≤M≤8.4, excluding the aftershocks of strong events. We used the Slickenside analysis package of Michael’s method. The stress field we obtained shows an extensional regime in the Mid-Atlantic Ridge, Terceira Ridge and Azores Islands and a strike-slip regime along the Gloria Fault, Gorringe Bank, and Gulf of Cadiz, to southern Spain. The same regime is also observed in the Rif and Alboran Sea. The stress regime becomes compressional in western Algeria, with strike-slip in eastern and southern Tunisia and an exception in northern Tunisia, where the stress exhibits a reverse rupture process. This study leads us to propose a new sketch of the present stress field along the western part of the Eurasia–Africa plate boundary.","PeriodicalId":12359,"journal":{"name":"Frontiers in Earth Science","volume":null,"pages":null},"PeriodicalIF":2.0000,"publicationDate":"2024-06-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Frontiers in Earth Science","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.3389/feart.2024.1366156","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
Complex deformation is observed along the plate boundary between the Africa and Eurasia plates, this complexity is highlighted by the faulting mechanism changing from normal faulting at the Mid-Atlantic Ridge to thrust and strike-slip faulting in the Ibero-Maghreb region (Iberia, Morocco, Algeria and Tunisia). The geodynamics of the study area shows the occurrence of NW‒SE convergence between the two plates, with anticlockwise rotation. An updated scheme of the pattern of the tectonic stress direction from the Azores Archipelago to the Tunisian Atlas is presented, along with the analysis of the principal stress axis orientations (Shmax = σ1, Shmin = σ3) from the inversion of fault plane solutions. We used a catalogue of 557 fault plane solutions with only main shocks without considering the related aftershock solutions for the period from 1931 to 2020. This study complements previous work limited to Algeria and eastern Morocco by inverting earthquake mechanisms of aftershock sequences of strong events that occurred in Al Hoceima (Morocco), El Asnam, Chenoua-Tipasa, Zemmouri and Constantine (Algeria). The present work includes the area from Tunisia to the Mid-Atlantic Ridge. The inversion considers only the earthquake mechanisms of events 4.0≤M≤8.4, excluding the aftershocks of strong events. We used the Slickenside analysis package of Michael’s method. The stress field we obtained shows an extensional regime in the Mid-Atlantic Ridge, Terceira Ridge and Azores Islands and a strike-slip regime along the Gloria Fault, Gorringe Bank, and Gulf of Cadiz, to southern Spain. The same regime is also observed in the Rif and Alboran Sea. The stress regime becomes compressional in western Algeria, with strike-slip in eastern and southern Tunisia and an exception in northern Tunisia, where the stress exhibits a reverse rupture process. This study leads us to propose a new sketch of the present stress field along the western part of the Eurasia–Africa plate boundary.
期刊介绍:
Frontiers in Earth Science is an open-access journal that aims to bring together and publish on a single platform the best research dedicated to our planet.
This platform hosts the rapidly growing and continuously expanding domains in Earth Science, involving the lithosphere (including the geosciences spectrum), the hydrosphere (including marine geosciences and hydrology, complementing the existing Frontiers journal on Marine Science) and the atmosphere (including meteorology and climatology). As such, Frontiers in Earth Science focuses on the countless processes operating within and among the major spheres constituting our planet. In turn, the understanding of these processes provides the theoretical background to better use the available resources and to face the major environmental challenges (including earthquakes, tsunamis, eruptions, floods, landslides, climate changes, extreme meteorological events): this is where interdependent processes meet, requiring a holistic view to better live on and with our planet.
The journal welcomes outstanding contributions in any domain of Earth Science.
The open-access model developed by Frontiers offers a fast, efficient, timely and dynamic alternative to traditional publication formats. The journal has 20 specialty sections at the first tier, each acting as an independent journal with a full editorial board. The traditional peer-review process is adapted to guarantee fairness and efficiency using a thorough paperless process, with real-time author-reviewer-editor interactions, collaborative reviewer mandates to maximize quality, and reviewer disclosure after article acceptance. While maintaining a rigorous peer-review, this system allows for a process whereby accepted articles are published online on average 90 days after submission.
General Commentary articles as well as Book Reviews in Frontiers in Earth Science are only accepted upon invitation.