Investigating Strike-Slip Faulting Parallel to the Icelandic Plate Boundary Using Boundary Element Models

2021 ◽  
Author(s):  
Anna Pearson ◽  
John P. Loveless
Keyword(s):  
Boundary Element ◽  
Plate Boundary ◽  
Strike Slip

Newly identified strike-slip plate boundary in the northeastern Arabian Sea

Geology ◽  
2000 ◽  
Vol 28 (4) ◽  
pp. 355 ◽  
Author(s):  
Nina Kukowski ◽  
Thies Schillhorn ◽  
Ernst R. Flueh ◽  
Katrin Huhn
Keyword(s):  
Arabian Sea ◽  
Plate Boundary ◽  
Strike Slip

scholarly journals Constraints on the rheology of the lower crust in a strike-slip plate boundary: evidence from the San Quintín xenoliths, Baja California, Mexico

Solid Earth ◽  
2017 ◽  
Vol 8 (6) ◽  
pp. 1211-1239 ◽  
Author(s):  
Thomas van der Werf ◽  
Vasileios Chatzaras ◽  
Leo Marcel Kriegsman ◽  
Andreas Kronenberg ◽  
Basil Tikoff ◽  
...  
Keyword(s):  
Grain Size ◽  
Upper Mantle ◽  
Lower Crust ◽  
Baja California ◽  
Plate Boundary ◽  
Volcanic Field ◽  
Strike Slip ◽  
Low Viscosity ◽  
The Pacific ◽  
Flow Laws

Abstract. The rheology of lower crust and its transient behavior in active strike-slip plate boundaries remain poorly understood. To address this issue, we analyzed a suite of granulite and lherzolite xenoliths from the upper Pleistocene–Holocene San Quintín volcanic field of northern Baja California, Mexico. The San Quintín volcanic field is located 20 km east of the Baja California shear zone, which accommodates the relative movement between the Pacific plate and Baja California microplate. The development of a strong foliation in both the mafic granulites and lherzolites, suggests that a lithospheric-scale shear zone exists beneath the San Quintín volcanic field. Combining microstructural observations, geothermometry, and phase equilibria modeling, we estimated that crystal-plastic deformation took place at temperatures of 750–890 °C and pressures of 400–560 MPa, corresponding to 15–22 km depth. A hot crustal geotherm of 40 ° C km−1 is required to explain the estimated deformation conditions. Infrared spectroscopy shows that plagioclase in the mafic granulites is relatively dry. Microstructures are interpreted to show that deformation in both the uppermost lower crust and upper mantle was accommodated by a combination of dislocation creep and grain-size-sensitive creep. Recrystallized grain size paleopiezometry yields low differential stresses of 12–33 and 17 MPa for plagioclase and olivine, respectively. The lower range of stresses (12–17 MPa) in the mafic granulite and lherzolite xenoliths is interpreted to be associated with transient deformation under decreasing stress conditions, following an event of stress increase. Using flow laws for dry plagioclase, we estimated a low viscosity of 1.1–1.3×1020 Pa ⋅ s for the high temperature conditions (890 °C) in the lower crust. Significantly lower viscosities in the range of 1016–1019 Pa ⋅ s, were estimated using flow laws for wet plagioclase. The shallow upper mantle has a low viscosity of 5.7×1019 Pa ⋅ s, which indicates the lack of an upper-mantle lid beneath northern Baja California. Our data show that during post-seismic transients, the upper mantle and the lower crust in the Pacific–Baja California plate boundary are characterized by similar and low differential stress. Transient viscosity of the lower crust is similar to the viscosity of the upper mantle.

Interseismic stress field variations in Hjalli-Ölfus, SW Iceland

2020 ◽  
Author(s):  
Ingi Th. Bjarnason ◽  
Revathy M. Parameswaran ◽  
Bergthóra S. Thorbjarnardóttir
Keyword(s):  
Plate Boundary ◽  
Strike Slip ◽  
Seismogenic Zone ◽  
Plate Boundaries ◽  
Central Volcano ◽  
Seismic Zone ◽  
Stress Regime ◽  
Mid Atlantic Ridge ◽  
Spatio Temporal ◽  
Earthquake Sequences

<p>Western South Iceland Seismic Zone (SISZ) plate boundary lies adjacent to the Hengill central volcano. The sinistral SISZ connects the two arms of the divergent Mid-Atlantic Ridge (MAR) plate boundaries (Western and Eastern Volcanic Zones; WVZ, EVZ), while Hengill is a part of the WVZ. Seismicity in western SISZ, also known as the Hjalli-Ölfus region, closely interacts with the seismicity and magmatism in Hengill. For instance, the  4 June 1998 Mw 5.4 Hengill earthquake witnessed aftershocks that extended south to meet the Hjalli-Ölfus segment. This segment then hosted the Mw 5.1 Hjalli-Ölfus earthquake that occurred on 13 November 1998; elucidating the Hengill-Ölfus interaction. Relative relocations of earthquakes from July 1991 to December 1999 in Hjalli-Ölfus indicate that the seismogenic zone is predominant at 4-8 km depth, with 80% of the events occuring along an ~ENE-WSW trending seismic zone with lateral extension of ~12 km. The remaining occur along N-S faults, much like the observed norm of dextral faulting along the rest of the SISZ (e.g., 17 June 2000, 29 May 2008 earthquakes; Árnadottir et al., 2001; Brandsdottir et al., 2010). These relocated earthquake sequences were used to perform stress inversions within specified spatio-temporal grids. The results show that from 1994 to 1997, the western part of the Hjalli-Ölfus region exhibits an oblique normal stress regime, while the eastern part remains consistently strike-slip in nature. From mid-1997 to June 1998 western Hjalli-Ölfus shifts from an oblique normal to a strike-slip stress regime, while the eastern part maintains the strike-slip character of the SISZ. However, two months after the 4 June 1998 Hengill earthquake, the western part shifts back to an oblique normal regime, which loses a part of its normal-faulting tendency after the 13 November 1998 Hjalli-Ölfus earthquake. This variation in stress fields between two significant events on conjugately oriented prodominantly strike-slip faults is a clear example of these features influencing one another between seismic episodes. </p>

scholarly journals Propagation of a strike-slip plate boundary within an extensional environment: the westward propagation of the North Anatolian Fault

2016 ◽  
Vol 53 (11) ◽  
pp. 1416-1439 ◽  
Author(s):  
Xavier Le Pichon ◽  
A.M. Celâl Şengör ◽  
Julia Kende ◽  
Caner İmren ◽  
Pierre Henry ◽  
...  
Keyword(s):  
Plate Boundary ◽  
Strike Slip ◽  
Fault System ◽  
Plate Boundaries ◽  
Sea Of Marmara ◽  
The North ◽  
Gulf Of Corinth ◽  
Northern Border ◽  
North Aegean ◽  
Narrow Plate

We document the establishment of the Aegea–Anatolia/Eurasia plate boundary in Pliocene–Pleistocene time. Before 2 Ma, no localized plate boundary existed north of the Aegean portion of the Anatolia plate and the shear produced by the motion of Anatolia–Aegea with respect to Eurasia was distributed over the whole width of the Aegean – West Anatolian western portion. In 4.5 Ma, a shear zone comparable to the Gulf of Corinth was formed in the present Sea of Marmara. The initial extensional basins were cut by the strike-slip Main Marmara Fault system after 2.5 Ma. Shortly after, the plate boundary migrated west of the Sea of Marmara along the northern border of Aegea from the North Aegean Trough, to the Gulf of Corinth area and to the Kefalonia Fault. There, it finally linked with the northern tip of the Aegean subduction zone, completing the system of plate boundaries delimiting the Anatolia–Aegea plate. We have related the change in the distribution of shear from Miocene to Pliocene to the formation of a relatively undeforming Aegea block in Pliocene that forced the shear to be distributed over a narrow plate boundary to the north of it. We attribute the formation of this block to the northeastward progression of the oceanic Ionian slab. We propose that the slab cuts the overlying lithosphere from asthenospheric sources and induces a shortening environment over it.

New c. 270 kyr strike-slip and uplift rates for the southern Alpine Fault and implications for the New Zealand plate boundary

2014 ◽  
Vol 64 ◽  
pp. 39-52 ◽  
Author(s):  
N.C. Barth ◽  
D.K. Kulhanek ◽  
A.G. Beu ◽  
C.V. Murray-Wallace ◽  
B.W. Hayward ◽  
...  
Keyword(s):  
New Zealand ◽  
Plate Boundary ◽  
Strike Slip ◽  
Alpine Fault ◽  
Uplift Rates

Concluding remarks

1990 ◽  
Vol 331 (1620) ◽  
pp. 643-647
Keyword(s):  
Wide Spectrum ◽  
Plate Boundary ◽  
Strike Slip ◽  
Data Handling ◽  
Huge Amount ◽  
The North ◽  
Tectonic Processes ◽  
Regional Tectonic ◽  
Plate Boundary Zone ◽  
Orogenic Belts

During the course of this Discussion Meeting, a very large amount of regional tectonic geology was displayed, and debated critically in a terrane framework, on scales ranging from the whole of the North American Precambrian or the Mesozoic-Cenozoic Tethys down to particular segments of the Caledonides and Alpides. A wide spectrum of opinion was expressed from those who believe that the terrane methodology is a critical and essential objective stage in data handling before any rational palaeogeographic and palaeotectonic synthesis can be attempted in plate boundary zones to those who believe that the terrane philosophy is fundamentally flawed, dangerous, and pernicious, in that it leads to random data collection and the obscuring of fundamental plate tectonic processes. Another view was that terranology has been useful in drawing our attention to the importance of large pre-collisional strike—slip or transform motions in orogenic belts and the juxtaposition of disparate elements and zones. Yet another position was that there is nothing new in terranology that is not implicitly and explicitly inherent in plate boundary processes and that terrane analysis is simply another harmless word for what most careful regional geological synthesizers have been doing since the early 1970s. Naturally, no coherent consensus view emerged from the discussion, but an important result was that a huge amount of excellent regional and global geology and tectonic ideas were discussed in the context of the problems and complexities of plate boundary zone evolution and the mechanisms by which objects from the size of ‘knockers’ to continents, detach, move and weld to form collages at all scales.

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