Types Of Deformation Structures Research Articles

Relationship of deformation meso- and macrostructures types with the staging of damage accumulation in welded joints of stainless steel under high-cycle fatigue

ABSTRACT The fatigue fracture mechanism of spot-welded joints of stainless constructional steel at multi-cycle loading condition is studied using the method of digital images correlation. Analysis of deformation meso- and macrostructures was carried out within the framework of the four-stage scheme of deformation and fracture of welded joints identified in the work. Characteristic fields of displacement vectors are presented and quantitative indicators and duration of damage accumulation stages are determined. On the basis of inverse pseudo-images, new types of deformation structures (trickle and cellular hexagonal) have been discovered.

Liquefaction structures induced by the M5.7 earthquake on May 28, 2018 in Songyuan, Jilin Province, NE China and research implication

An earthquake of magnitude M5.7 occurred in Yamutu village, Songyuan City, Jilin Province, NE China (45°16′12″N/124°42′35″E) on May 28, 2018, with a focal depth of 13 km. The epicenter is located at the intersection of the Fuyu/Songyuan-Zhaodong Fault, Second Songhua River Fault and Fuyu North Fault which lies northwest of Tancheng-Lujiang Fault (Tan-Lu Fault). The earthquake-induced widespread liquefaction structures and ground surface fissures within 3 km from the epicenter, caused serious disasters to the local surroundings. The visible liquefied structures include sand volcanoes, liquefied sand mounds, sand dikes and sand sills. Sand volcanoes can be divided into sand volcano with a crater, sand volcano without a crater and water volcano (no sand). Other soft-sediment deformation structures (SSDS) induced by the earthquake include deformation lamination, load and flame structures, deformation folds, dish structures, convolute bedding and water-escape structures. The formation process of the sand volcanoes comprises three stages: (1) building up excess pore-fluid pressure in the liquefied layer, (2) cracking of the low-permeable overlying layer, and (3) mixture of sand-water venting out of the ground surface. During the upward movement, the liquefied sand is injected into the low-permeable layer to form sand veins, sand sills and various types of deformation structures. Vertical distribution of seismic liquefaction structure can be divided into four zones: the thoroughly liquefied zone, the lower liquefied zone with SSDS, the upper liquefied zone with SSDS, and the ground surface liquefied zone. The liquefaction occurred at a burial depth of 2–5 m, and the thickness of liquefied sand is 2 m. NE-SW (35°–215°) trending compressive stress is possibly the seismogenic trigger of the Songyuan M5.7 earthquake that caused the fault (Fuyu/Songyuan-Zhaodong Fault) to reactivate. The study of the Songyuan seismic liquefaction structures gives insight into the prediction of modern earthquakes and disaster-prone areas. Meanwhile it provides abundant basic material for studying earthquake-induced SSDS in both ancient and modern sediments. The research is obviously of great significance to reveal that the northern Tan-Lu Fault has entered a stage of active seismic activity since the twenty-first century.

Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean

Large-magnitude intraplate earthquakes within the ocean basins are not well understood. The Mw 8.6 and Mw 8.2 strike-slip intraplate earthquakes on 11 April 2012, while clearly occurring in the equatorial Indian Ocean diffuse plate boundary zone, are a case in point, with disagreement on the nature of the focal mechanisms and the faults that ruptured. We use bathymetric and seismic reflection data from the rupture area of the earthquakes in the northern Wharton Basin to demonstrate pervasive brittle deformation between the Ninetyeast Ridge and the Sunda subduction zone. In addition to evidence of recent strike-slip deformation along approximately north-south–trending fossil fracture zones, we identify a new type of deformation structure in the Indian Ocean: conjugate Riedel shears limited to the sediment section and oriented oblique to the north-south fracture zones. The Riedel shears developed in the Miocene, at a similar time to the onset of diffuse deformation in the central Indian Ocean. However, left-lateral strike-slip reactivation of existing fracture zones started earlier, in the Paleocene to early Eocene, and compartmentalizes the Wharton Basin. Modeled rupture during the 11 April 2012 intraplate earthquakes is consistent with the location of two reactivated, closely spaced, approximately north-south–trending fracture zones. However, we find no evidence for WNW-ESE–trending faults in the shallow crust, which is at variance with most of the earthquake fault models.

Evidences of quaternary paleoseismicity in hydromagmatics deposits in the Campo de Calatrava volcanic region (central Spain)

Resumen

Kilometre-scale polygonal seabed depressions in the Hatton Basin, NE Atlantic Ocean: Constraints on the origin of polygonal faulting

Polygonal faulting is a widespread phenomenon in sedimentary basins worldwide. It changes basin-scale fluid flow patterns and alters the physical properties of the sediments making it important for hydrocarbon exploration and geohazard analysis. It is generally accepted that polygonal fault patterns derive from dewatering and compaction of the host sediments, but there is debate regarding the processes that control polygonal faulting. New multibeam-bathymetry data from the Hatton Basin, NE Atlantic, show up to 10 m deep and 200–600 m wide troughs at the seabed. They connect to each other forming polygons that are several hundred metres across, i.e. of similar size as buried polygonal fault systems observed in 3D seismic data. The troughs are symmetrical and resemble elongated pockmarks. Previously unpublished high-resolution 2D seismic data from the same area show seismic disturbance zones similar to pipes observed under pockmarks elsewhere as well as faults that have all the characteristics of polygonal fault systems. The observation of the wide disturbance zones is enigmatic, as they appear to follow the polygonal seafloor pattern. The observed extent of the polygonal sediment contraction system is substantial covering almost 37,000 km 2 . We calculate that some 2600 km 3 of possibly carbon-bearing fluids have been expelled from this system and we expect that this will affect the benthic ecosystems, although so far there is only limited evidence for chemosynthetic habitats. ► Polygonal seabed depressions cover 37,000 km 2 . ► They are underlain by 2 types of deformation structures. ► Some of the seabed depressions are not linked to polygonal faults. ► Dewatering has released about 2600 km 3 of fluids to the seafloor.

Palaeoproterozoic seismites (fine-grained facies of the Chaibasa Formation, east India) and their soft-sediment deformation structures

Abstract Metamorphosed shales, heterolithic deposits and sandstones build up the Palaeoproterozoic Chaibasa Formation in east India. The shales (referred here to as the fine-grained facies) comprising mudstone (clay and silt size) with some minor amounts of very fine to fine sandstone were deposited below storm wave base in a deep marine basin that simultaneously underwent tectonic activity. This fine-grained facies contains strongly deformed layers, intercalated between undeformed layers. Sedimentological analysis of the deformations indicates that they formed while still in an unconsolidated or slightly consolidated state, partly during and after sedimentation, but before being covered by younger sediments. The types of deformation structures indicate an earthquake-induced origin. Thus, they should be considered as seismites. The soft-sediment deformation structures in the seismites show a wide variety of shapes and other characteristics that appear to depend on their relative position to the epicentre of the earthquake.

Deformation Twins and Stacking Faults in an AA5182 Al-Mg Alloy Processed by High Pressure Torsion

High-resolution transmission electron microscopy investigations revealed different types of deformation structures in a nanostructured commercial Al–Mg alloy processed by high pressure torsion at room temperature. Microtwins and stacking faults were detected within both nanocrystalline grains and ultrafine grains. Full dislocations in the form of dipoles were observed within grains and near the grain boundaries. Two twinning mechanisms previously predicted by molecular-dynamics simulations were directly verified including the heterogeneous twins nucleated by the successive emission of Shockley partials from grain boundaries and homogeneous twins formed in the grain interiors by the dynamic overlapping of stacking faults. Hence, the formation of full dislocations, stacking faults and twins in the present aluminum alloy subjected to severe plastic deformation may be interpreted in terms of molecular-dynamics simulations based on generalized planar fault energy curves for pure metal systems.

Structures in deposits from beach recovery, after erosion by swell waves around the southwestern coast of Aruba (Netherlands Antilles)

Hurricane- or storm-generated swell waves may cause erosion and deposition along coasts which are situated thousands of kilometers outside the generating wind field. Marked beach erosion, caused by such swell waves, was observed along the micro-tidal west coast of Aruba. During the process of erosion a swash bar was formed, which moved up-beach during the waxing part of the swell event. The swash bar welded to the beach during the waning part of the event. Rapid sedimentation occurred on the upper beach. Finally, recovery of the beach was observed. The formation of a swash bar was attributed to an erosive, dissipative interval of a normally accretionary reflective beach. The sedimentary structures, although generally in line with observations on other beaches, show several peculiar characteristics: (1) the great thickness of the laminae in these calcareous sands; (2) the succession of low-angle sigmoidal and tangential sets in the swash bar; (3) the relatively steep erosional lower set boundaries and the wedge-shaped lamination in the successive stages of beach recovery; and (4) the several types of deformation structures.

Chert 'dike' structures in Senonian chert beds, southern Negev, Israel

Three zones of chert beds showing a new type of deformation structure--chert dikes--have been found in the Senonian Sayyarim Formation in southern Israel. The dikes occur as a series of parallel bulges protruding both upwards and downwards from chert beds, deforming and intruding adjacent layers. The height of the dikes varies from a few millimeters to a few meters, while distances between adjacent structures vary between a few millimeters to a few tens of centimeters. The trend of the dike structures, being consistent on a regional scale (N70E), is roughly parallel to the facies boundaries within the discussed sequence. Petrographic study indicates that the structures were formed by plastic deformation followed by non-plastic brecciation. Structural relationships, such as rupturing of carbonate beds by the chert dikes, indicate that lithification of siliceous sediments may he rather slow compared to other sediments. It is suggested that the dike-like structures are formed by an increase in volume of the siliceous sediment during diagenesis, the expansion being regionally controlled.