Recent Geodetic Results in the Azores Triple Junction Region

2004 ◽  
Vol 161 (3) ◽  
pp. 683-699 ◽  
Author(s):  
R. M. S. Fernandes ◽  
L. Bastos ◽  
B. A. C. Ambrosius ◽  
R. Noomen ◽  
S. Matheussen ◽  
...  
Keyword(s):  
Triple Junction ◽  
Junction Region ◽  
Azores Triple Junction

Recent Geodetic Results in the Azores Triple Junction Region

2004 ◽  
pp. 683-699
Author(s):  
R. M. S. Fernandes ◽  
L. Bastos ◽  
B. A. C. Ambrosius ◽  
R. Noomen ◽  
S. Matheussen ◽  
...  
Keyword(s):  
Triple Junction ◽  
Junction Region ◽  
Azores Triple Junction

Plate boundary deformation at the Azores triple junction determined from continuous GPS geodetic measurements, 2002-2017

2021 ◽  
Author(s):  
João D'Araújo ◽  
Freysteinn Sigmundsson ◽  
Teresa Ferreira ◽  
Jun Okada ◽  
Maria Lorenzo ◽  
...  
Keyword(s):  
Triple Junction ◽  
Plate Boundary ◽  
Geodetic Measurements ◽  
Azores Triple Junction ◽  
Plate Boundary Deformation ◽  
Boundary Deformation ◽  
Continuous Gps

The rupture process and aftershock distribution of the 6 April 1992 MS 6.8 earthquake, Offshore British Columbia

1995 ◽  
Vol 85 (3) ◽  
pp. 716-735 ◽  
Author(s):  
John F. Cassidy ◽  
Garry C. Rogers
Keyword(s):  
Surface Waves ◽  
Triple Junction ◽  
Rupture Process ◽  
Body Waves ◽  
Ocean Bottom Seismometer ◽  
Strain Accumulation ◽  
Transform Fault ◽  
Junction Region ◽  
Long Period ◽  
Initial Rupture

Abstract On 6 April 1992, a magnitude 6.8 (MS) earthquake occurred in the triple-junction region at the northern end of the Cascadia subduction zone. This was the largest earthquake in at least 75 yr to occur along the 110-km-long Revere-Dellwood-Wilson (RDW) transform fault and the first large earthquake in this region recorded by modern broadband digital seismic networks. It thus provides an opportunity to examine the rupture process along a young (<2 Ma) oceanic transform fault and to gain better insight into the tectonics of this triple-junction region. We have investigated the source parameters and the rupture process of this earthquake by modeling broadband body waves and long-period surface waves and by accurately locating the mainshock and the first 10 days of aftershocks using a well-located “calibration” event recorded during an ocean-bottom seismometer survey. Analysis of P and SH waveforms reveals that this was a complex rupture sequence consisting of three strike-slip subevents in 12 sec. The initial rupture occurred 5 to 6 km to the SW of the seafloor trace of the RDW fault at 50.55° N, 130.46° W. The dominant subevent occurred 2 to 3 sec later and 4.3 km beneath the seafloor trace of the RDW fault, and a third subevent occurred 5 sec later, 18 km to the NNW, suggesting a northwestward propagating rupture. The aftershock sequence extended along a 60- to 70-km-long segment of the RDW fault, with the bulk of the activity concentrated ∼30 to 40 km to the NNW of the epicenter, consistent with this interpretation. The well-constrained mechanism of the initial rupture (strike/dip/slip 339°/90°/−168°) and of the largest aftershock (165°/80°/170°) are rotated 15° to 20° clockwise relative to the seafloor trace of the RDW fault but are parallel to the Pacific/North America relative plate motion vector. In contrast, the mechanisms of the dominant subevent (326°/87°/−172°), and the long-period solution derived from surface waves aligns with the RDW fault. This suggests that small earthquakes (M < 6) in this area occur along faults that are optimally aligned with respect to the regional stress field, whereas large earthquakes, involving tens of kilometers of rupture, activate the RDW fault. For the mainshock, we estimate a seismic moment (from surface waves) of 1.0 × 1026 dyne-cm, a stress drop of 60 bars, and an average slip of 1.2 m. This represents only 21 yr of strain accumulation, implying that there is either a significant amount of aseismic slip along the RDW fault or that much of the strain accumulation manifests itself as deformation within the Dellwood and Winona blocks or along the continental margin.

scholarly journals Volcano-tectonic evolution of a linear volcanic ridge (Pico-Faial Ridge, Azores Triple Junction) assessed by paleomagnetic studies

2018 ◽  
Vol 352 ◽  
pp. 78-91 ◽  
Author(s):  
Pedro F. Silva ◽  
Bernard Henry ◽  
Fernando O. Marques ◽  
Anthony Hildenbrand ◽  
Ana Lopes ◽  
...  
Keyword(s):  
Triple Junction ◽  
Tectonic Evolution ◽  
Azores Triple Junction

scholarly journals Microstructure Characteristics and Its Effect on the Fracture in the Triple Junction Region of Friction Stir Welded Mg Alloys Subjected to Tension

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3672
Author(s):  
Guodong Liu ◽  
Qunying Yang ◽  
Yongshan Cheng
Keyword(s):  
Triple Junction ◽  
Weld Zone ◽  
Base Material ◽  
Junction Region ◽  
Friction Stir ◽  
Microstructure Characteristics ◽  
Transverse Tension ◽  
Twin Band ◽  
Zone Edge ◽  
Electron Back Scattered Diffraction

Because of the tensile strength decreasing of the friction stir welded wrought magnesium (Mg) alloy compared to the base material, the reasons for the failure of weld has been focused on. After the fracture in transverse tension, the crack went through the welded joint from the center of the weld to the transition zone between the thermal-mechanical affected zone and weld zone. In the present study, the microstructure characteristics and its effect on the facture in the triple junction region is investigated. Based on the metallography and the electron back-scattered diffraction (EBSD) technology, it was observed that a twin band extended from the triple junction region to the middle of weld. The profuse twinning in the twin band was considered to play an important role on the crack propagation from the stir zone edge to the crown zone.

scholarly journals Multi-stage evolution of a sub-aerial volcanic ridge over the last 1.3 Myr: S. Jorge Island, Azores Triple Junction

2008 ◽  
Vol 273 (3-4) ◽  
pp. 289-298 ◽  
Author(s):  
Anthony Hildenbrand ◽  
Pedro Madureira ◽  
Fernando Ornelas Marques ◽  
Inês Cruz ◽  
Bernard Henry ◽  
...  
Keyword(s):  
Triple Junction ◽  
Multi Stage ◽  
Azores Triple Junction

Geodynamic models for the Azores triple junction: A contribution from tectonics

1990 ◽  
Vol 184 (3-4) ◽  
pp. 405-415 ◽  
Author(s):  
José Madeira ◽  
António Ribeiro
Keyword(s):  
Triple Junction ◽  
Azores Triple Junction ◽  
Geodynamic Models
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