Dynamical Instability Produces Transform Faults at Mid-Ocean Ridges

Science ◽  
2010 ◽  
Vol 329 (5995) ◽  
pp. 1047-1050 ◽  
Author(s):  
T. Gerya
Keyword(s):  
Dynamical Instability ◽  
Transform Faults ◽  
Ocean Ridges

3. Fracture zones and transform faults

2015 ◽  
pp. 36-52
Author(s):  
Peter Molnar
Keyword(s):  
Fracture Zones ◽  
Transform Faults ◽  
Ocean Ridges ◽  
The 1950S

‘Fracture zones and transform faults’ introduces fracture zones, huge, long linear scars in the seafloor first mapped in the 1950s, and their interpretation in terms of a new concept, transform faulting. Fracture zones are made at mid-ocean ridges, where the seafloor spreads apart. Segments of zones of spreading intersect fracture zones at right angles, along which transform faulting transfers the spreading on one spreading zone to another. As the seafloor spreads, and plates move apart at mid-ocean ridges, fracture zones grow longer. Testing this idea relied on the study of earthquakes that occurred on the transform faults, using seismographs on distant continents. This chapter introduces readers to the pertinent seismological methods by which this was achieved.

scholarly journals MAGNETIC CHARACTERISTICS OF METAMORPHIZED ULTRABASITES OF THE OCEANIC LITHOSPHERE

2019 ◽  
Vol 47 (4) ◽  
pp. 106-127
Author(s):  
K. V. Popov ◽  
A. M. Gorodnitskiy ◽  
N. A. Shishkina
Keyword(s):  
World Ocean ◽  
Oceanic Lithosphere ◽  
Structural Features ◽  
Residual Magnetization ◽  
Magnetic Characteristics ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Submarine Ridge ◽  
Deep Layers ◽  
The Stability

As part of the study of the nature of magnetic anomalies associated with the deep layers of the oceanic crust, a comparative analysis was made of the petromagnetic characteristics of serpentinized mantle ultrabasic samples taken from oceanographic expeditions of the Institute of Oceanology and the Institute of Geochemistry and Analytical Chemistry of the Russian Academy of Sciences in various morphotectonic regions of the World Ocean. The purpose of the work is to obtain information on the composition, concentration, crystallization temperature and structural features of ferromagnetic minerals, which are formed in different conditions of the post-magmatic metamorphism of ultrabasites. Sample collections are divided into three groups. 1. Oceanic peridotites from the rift zones of the mid-ocean ridges and transform faults. 2. Peridotites of the submarine ridge Gorringe, located within the Azoro-Gibraltar zone of faults. 3. Dunites of the Pekulney complex (Chukotka) formed in the island arc system. It has been established that in all selected regions, samples of serpentinized hyperbasites have high values of natural residual magnetization, magnetic susceptibility and saturation magnetization. The highest values of magnetic parameters are the dunites of the Pekulney complex. Estimation of the dependence of the concentration of ferrimagnetic materials C% of the degree of serpentinization of the SS%. showed that it is practically of little significance. The main factors contributing to the increase in the concentration of magnetite are the increased iron content of olivine in ultrabasites and the temperature of metamorphism. The question of the period of formation of magnetites and the stability of their primary residual magnetization requires further study.

scholarly journals Initiation of a Proto-transform Fault Prior to Seafloor Spreading

2020 ◽  
Author(s):  
Finnigan Illsley-Kemp ◽  
JM Bull ◽  
D Keir ◽  
T Gerya ◽  
C Pagli ◽  
...  
Keyword(s):  
Plate Tectonics ◽  
Seafloor Spreading ◽  
Continental Rift ◽  
Formation Mechanisms ◽  
Transform Fault ◽  
Transform Faults ◽  
Local Seismicity ◽  
Ocean Ridges ◽  
Rifted Margins ◽  
Direct Observations

©2018. The Authors. Transform faults are a fundamental tenet of plate tectonics, connecting offset extensional segments of mid-ocean ridges in ocean basins worldwide. The current consensus is that oceanic transform faults initiate after the onset of seafloor spreading. However, this inference has been difficult to test given the lack of direct observations of transform fault formation. Here we integrate evidence from surface faults, geodetic measurements, local seismicity, and numerical modeling of the subaerial Afar continental rift and show that a proto-transform fault is initiating during the final stages of continental breakup. This is the first direct observation of proto-transform fault initiation in a continental rift and sheds unprecedented light on their formation mechanisms. We demonstrate that they can initiate during late-stage continental rifting, earlier in the rifting cycle than previously thought. Future studies of volcanic rifted margins cannot assume that oceanic transform faults initiated after the onset of seafloor spreading.

scholarly journals Seismicity characterization of oceanic earthquakes in the Mexican territory

2020 ◽  
Author(s):  
Quetzalcoatl Rodríguez-Pérez ◽  
Víctor Hugo Márquez-Ramírez ◽  
Francisco Ramón Zúñiga
Keyword(s):  
Normal Fault ◽  
B Value ◽  
Statistical Characteristics ◽  
P Value ◽  
Transform Faults ◽  
Frequency Distributions ◽  
Ocean Ridges ◽  
The Pacific ◽  
Stress Orientations ◽  
Clear Differentiation

Abstract. We analyzed the seismicity of oceanic earthquakes in the Pacific oceanic regime of Mexico. We used data from the earthquake catalogs of the Mexican National Service (SSN), and the International Seismological Center (ISC) from 1967 to 2017. Events were classified into two different categories: intraplate oceanic (INT), and transform faults zone and mid-ocean ridges events (TF-MOR), respectively. For each category, we determined statistical characteristics such as magnitude frequency distributions, the aftershocks decay rate, the non-extensivity parameters, and the regional stress field. We obtained b-values of 1.17, and 0.82 for the INT, and TF-MOR events, respectively. TF-MOR events also exhibit local b-value variations in the range of 0.72–1.30. TF-MOR events follow a tapered Gutenberg-Richter distribution. We also obtained a p-value of 0.67 for the 1 May 1997 (Mw = 6.9) earthquake. By analyzing the non-extensivity parameters, we obtained similar q-values in the range of 1.39–1.60 for both types of earthquakes. On the other hand, the parameter a showed a clear differentiation, being higher for TF-MOR events than for INT events. This implies that more energy is released for TF-MOR events. Stress orientations are in agreement with geodynamical models for transform faults zone and mid-ocean ridges zones. In the case of intraplate seismicity, stresses are mostly related to a normal fault regime.

MORGEN – The Mid Ocean Ridge GENerating algorithm

2021 ◽  
Author(s):  
Thomas van der Linden ◽  
Douwe van Hinsbergen
Keyword(s):  
Conceptual Knowledge ◽  
Smooth Curve ◽  
Weddell Sea ◽  
Plate Boundaries ◽  
Plate Tectonic ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Euler Pole ◽  
Mid Ocean Ridge ◽  
Ocean Ridge

<p>Paleo-digital elevation models (paleoDEM) based on plate tectonic and paleogeographic reconstructions use age grids of ocean floor to determine ocean bathymetry. In recent years, such age grids have also been developed for now-subducted oceans from the far geological past, as far back as the Neoproterozoic, using geology and paleomagnetism-based estimates of ocean opening. In such reconstructions, mid ocean ridges are drawn based on estimated Euler poles and rotations, and conceptual knowledge on the geometry consisting of spreading ridges and transform faults.</p><p>Current procedures to draw mid ocean ridges in plate tectonic reconstructions are laborious, as new ridges are drawn every time the Euler pole location changes. Fortunately this is also a task that can be automated. We have written an algorithm using pyGPlates that takes as input a smooth curve at the approximate position of the reconstructed mid ocean ridge at the moment of its formation, and then calculates spreading and transform segments according to their typical geometries in modern oceans, assuming symmetric spreading. The algorithm allows gradual readjustment of ridge orientations upon Euler pole changes comparable to documented cases in the modern oceans (e.g., in the Weddell Sea). The algorithm also contains modules that can convert the calculated mid ocean ridges with other plate boundaries to boundary topologies – which can be used as input for the recently published TracerTectonics algorithm, produce isochrons which can be converted to age grids, check for subduction of isochrons and subsequently create bathymetry grids. We illustrate the use of the MORGEN algorithm with recently published reconstructions of subducted, as well as future oceans.</p>

All at Sea

2018 ◽  
Author(s):  
Roy Livermore
Keyword(s):  
Plate Tectonics ◽  
First Generation ◽  
Basaltic Magma ◽  
Ocean Floor ◽  
Tennis Ball ◽  
Magma Chambers ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Sea Floor Spreading ◽  
Ocean Ridge

According to first-generation plate tectonics, sea-floor spreading was nice and simple. Plates were pulled apart at mid-ocean ridges, and weak mantle rocks rose to fill the gap and began to melt. The resulting basaltic magma ascended into the crust, where it ponded to form linear ‘infinite onion’ magma chambers beneath the mid-ocean tennis-ball seam. At frequent intervals, vertical sheets of magma rose from these chambers to the surface, where they erupted to form new ocean floor or solidified to form dykes, in the process acquiring a magnetization corresponding to the geomagnetic field at the time. Mid-ocean ridge axes were defined by rifted valleys and divided into segments by transform faults with offsets of tens to hundreds of kilometres, resulting in the staircase pattern seen on maps of the ocean floor. All mid-ocean ridges were thus essentially identical. Such a neat and elegant theory was bound to be undermined as new data were acquired in the oceans.

scholarly journals Semibrittle seismic deformation in high-temperature mantle mylonite shear zone along the Romanche transform fault

2021 ◽  
Vol 7 (15) ◽  
pp. eabf3388
Author(s):  
Zhiteng Yu ◽  
Satish C. Singh ◽  
Emma P. M. Gregory ◽  
Marcia Maia ◽  
Zhikai Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Plate Tectonics ◽  
Thermal Structure ◽  
Depth Range ◽  
Transform Fault ◽  
Equatorial Atlantic ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Equatorial Atlantic Ocean ◽  
Large Earthquakes

Oceanic transform faults, a key element of plate tectonics, represent the first-order discontinuities along mid-ocean ridges, host large earthquakes, and induce extreme thermal gradients in lithosphere. However, the thermal structure along transform faults and its effects on earthquake generation are poorly understood. Here we report the presence of a 10- to 15-kilometer-thick in-depth band of microseismicity in 10 to 34 kilometer depth range associated with a high-temperature (700° to 900°C) mantle below the brittle lithosphere along the Romanche mega transform fault in the equatorial Atlantic Ocean. The occurrence of the shallow 2016 moment magnitude 7.1 supershear rupture earthquake and these deep microearthquakes indicate that although large earthquakes occur in the upper brittle lithosphere, a substantial amount of deformation is accommodated in the semibrittle mylonitic mantle that resides at depths below the 600°C isotherm. We also observe a rapid westward deepening of this band of seismicity indicating a strong lateral heterogeneity.

scholarly journals Initiation of a Proto-transform Fault Prior to Seafloor Spreading

2020 ◽  
Author(s):  
Finnigan Illsley-Kemp ◽  
JM Bull ◽  
D Keir ◽  
T Gerya ◽  
C Pagli ◽  
...  
Keyword(s):  
Plate Tectonics ◽  
Seafloor Spreading ◽  
Continental Rift ◽  
Formation Mechanisms ◽  
Transform Fault ◽  
Transform Faults ◽  
Local Seismicity ◽  
Ocean Ridges ◽  
Rifted Margins ◽  
Direct Observations

©2018. The Authors. Transform faults are a fundamental tenet of plate tectonics, connecting offset extensional segments of mid-ocean ridges in ocean basins worldwide. The current consensus is that oceanic transform faults initiate after the onset of seafloor spreading. However, this inference has been difficult to test given the lack of direct observations of transform fault formation. Here we integrate evidence from surface faults, geodetic measurements, local seismicity, and numerical modeling of the subaerial Afar continental rift and show that a proto-transform fault is initiating during the final stages of continental breakup. This is the first direct observation of proto-transform fault initiation in a continental rift and sheds unprecedented light on their formation mechanisms. We demonstrate that they can initiate during late-stage continental rifting, earlier in the rifting cycle than previously thought. Future studies of volcanic rifted margins cannot assume that oceanic transform faults initiated after the onset of seafloor spreading.

An explanation for the orthogonality of ocean ridges and transform faults

1975 ◽  
Vol 80 (17) ◽  
pp. 2575-2585 ◽  
Author(s):  
Douglas W. Oldenburg ◽  
James N. Brune
Keyword(s):  
Transform Faults ◽  
Ocean Ridges

Rift linkage processes in areas of incipient oceanic spreading: examples from Afar

2020 ◽  
Author(s):  
Carolina Pagli ◽  
Alessandro La Rosa ◽  
Finnigan Illsley-Kemp
Keyword(s):  
Seafloor Spreading ◽  
Analytical Models ◽  
Fault System ◽  
Transform Fault ◽  
Transform Faults ◽  
Ocean Ridges ◽  
Oceanic Spreading ◽  
Moderate Seismicity ◽  
Deformation Patterns ◽  
Conjugate Fault

<p>Mid-ocean ridges are segmented and offset along their length. However, the kinematics of rift linkage and the initiation of oceanic transform faults in magmatic rifts remain debated. Crustal deformation patterns from the Afar continental rift provide evidences of how rifts grow to link in an area of incipient seafloor spreading. Here we present examples of rift linkage processes in Afar integrating seismicity and geodetic (InSAR and GPS) measurements, and explained by numerical and analytical models. We show that in central Afar overlapping spreading rifts link through zones of rift-perpendicular strike-slip faulting at the tips of the spreading rifts, demonstrating that distributed extension drives rift-perpendicular shearing. Conversely, in northern Afar we identify a linkage zone between the Erta Ale and Tat Ali segments where shear is accommodated by a conjugate set of oblique slip faults. There, InSAR modelling of a M<sub>L</sub> 5.1 earthquake in 2007 show that overall right-lateral shear is accommodated primarily by oblique left-lateral slip along faults subparallel to the rift segments but an active conjugate fault system with right-lateral slip is also highlighted by low-to-moderate seismicity during 2011-2013. Thermomechanical models of transform fault formation are consistent with the presence of a proto-transform fault that may develop into a throughgoing transform in the future. Our results provide evidences that offset rift segments during continental breakup can be linked by a wide variety of strain types and proto-transform zones can form before the onset of seafloor spreading.</p>

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