scholarly journals Supplementary material to "Correlation between tectonic stress regimes and methane seepage on the west-Svalbard margin"

2018 ◽  
Author(s):  
Andreia Plaza-Faverola ◽  
Marie Keiding
Keyword(s):  
Tectonic Stress ◽  
The West ◽  
Methane Seepage ◽  
Supplementary Material

scholarly journals Correlation between tectonic stress regimes and methane seepage on the west-Svalbard margin

2018 ◽  
Author(s):  
Andreia Plaza-Faverola ◽  
Marie Keiding
Keyword(s):  
Fluid Pressure ◽  
Tectonic Stress ◽  
Temporal Variations ◽  
Passive Margin ◽  
Morphological Evidence ◽  
Glacial Cycles ◽  
The West ◽  
Stress Regime ◽  
Near Surface ◽  
Methane Seepage

Abstract. Methane seepage occurs across the west-Svalbard margin at water depths ranging from the upper shelf at  1000 m. The Vestnesa sedimentary ridge, located on oceanic crust between 1000–1700 m water depth, hosts a perennially stable gas hydrate system with evidence of both past and present-day seepage. On the ridge, an eastward transition from a zone with clear morphological evidence of past seepage to a zone of active present-day seepage coincides with a change in the faulting pattern of near-surface strata. We modelled the tectonic stress regime due to oblique spreading along the Molloy and Knipovich spreading ridges to investigate whether spatial and temporal variations in the regional stress field may explain patterns of seepage distribution. The model reveals a zone of tensile stress that extends northward from the Knipovich Ridge and encompasses a zone of active seepage and extensional faulting. A zone of past seepage is presently located in a strike-slip regime. Our modelling results suggest that seepage is promoted by opening of faults and fractures in a tensile regime. We develop a conceptual model to describe how seepage may be controlled by an interplay between tectonic stresses and pore fluid pressure within shallow gas reservoirs across the passive margin off west-Svalbard. Glacio-isostatic flexural stresses may have influenced fluid dynamics along the Vestnesa Ridge in the past, explaining the presence of dormant pockmarks outside the ridge segment that is under a tensile regime at present and reconciling formerly suggested models of seepage periodicity linked to glacial cycles.

scholarly journals Study on the relationship between multi-stage strike-slip mechanism and basin evolution in Fangzheng fault depression

2018 ◽  
Vol 22 (4) ◽  
pp. 335-339
Author(s):  
Jingfeng Wu ◽  
Qi'an Meng ◽  
Xiaofei Fu ◽  
Yuling Ma ◽  
Meifeng Sun ◽  
...  
Keyword(s):  
Seismic Data ◽  
Structural Characteristics ◽  
Stage Structure ◽  
Tectonic Stress ◽  
Strike Slip ◽  
The West ◽  
Lateral Strike Slip ◽  
Slip Mechanism ◽  
Pull Apart Basin ◽  
Multi Stage

Fangzheng fault depression is controlled by the northern of the Tan-Lu fault zone. It undergoes multi-stage strike-slip, extrusion modification, and erosion of the thermal uplift, forming a tectonic pattern of uplifts connected with sags. Through the regional dynamic analysis, the study of the activity law of the western Pacific plate has clarified the formation and transformation of the regional tectonic stress field. Under the background of the multi-stage of the strike-slip mechanism in the northern part of the Tan-lu fault, the Fangzheng fault depression has a characteristic of the “left-lateral strike-slip pull-apart basin, right-lateral strike-slip extrusion transformation.” According to the difference of the strike-slip, the Fangzheng fault depression has divided into two parts: the East fault depression and the West fault depression. The seismic data, seismic attribute analysis, and geological modeling techniques have applied to analyze the two fault depressions, the East fault depression has actively controlled by the strike-slip activity, and the structure is complex. The seismic data quality is poor; the structure of the West Fault Depression is the opposite and structural characteristics of asymmetrical difference strike-slip in the East and West fault depressions. Interpretation of seismic sections through a slippery background, the strike-slip attributes of the whole fault depression from south to north are segmented, and the strike-slip mechanism from east to west is different. Under the control of the multi-stage strike-slip mechanism, the Fangzheng fault depression is divided into six stages of strike-slip evolution, corresponding to the six different stages of the strike-slip control basin, the formation process of the asymmetric difference strike-slip fault basin is clarified, which provides a reference for the study of the strike-slip pull-apart basin with multi-stage structure.

scholarly journals Velocity structure and the role of fluids in the West Bohemia Seismic Zone

2014 ◽  
Vol 6 (1) ◽  
pp. 511-534
Author(s):  
C. Alexandrakis ◽  
M. Calò ◽  
F. Bouchaala ◽  
V. Vavryčuk
Keyword(s):  
Velocity Structure ◽  
Weighted Average ◽  
Tectonic Stress ◽  
Double Difference ◽  
Seismic Zone ◽  
The West ◽  
Fluid Concentration ◽  
West Bohemia ◽  
Basic Characteristics ◽  
Tomography Method

Abstract. In this study, we apply the double-difference tomography method to investigate the detailed 3-D structure within and around the Nový Kostel seismic zone, an area in the Czech Republic known for frequent occurrences of earthquake swarms. We use data from the extensively analyzed 2008 swarm, which has known focal mechanisms, principal faults, tectonic stress, source migration and other basic characteristics. We selected about 500 microearthquakes recorded at 22 local seismic stations of the West Bohemia Network (WEBNET). Applying double-difference tomography, combined with Weighted Average Model post-processing to correct for parameter dependence effects, we produce and interpret 3-D models of the Vp-to-Vs ratio (Vp/Vs) in and around the focal zone. The modeled Vp-to-Vs ratio shows several distinct structures, namely an area of high Vp-to-Vs ratio correlating with the microearthquakes, and a layer of low values directly above it. These structures may reflect changes in lithology and/or fluid concentration. The overlaying low Vp-to-Vs ratio layer coincides with high density metamorphic unit associated with the Fichtelgebirge (Smrčiny) granitic intrusion. It is possible that the base of the layer acts as a fluid trap, resulting in the observed periodic swarms.

Sediment supply on the West Greenland passive margin: redirection of a large pre-glacial drainage system

2020 ◽  
Vol 177 (6) ◽  
pp. 1149-1160
Author(s):  
Scott Jess ◽  
Alexander L. Peace ◽  
Christian Schiffer
Keyword(s):  
Drainage System ◽  
Sediment Supply ◽  
Passive Margin ◽  
Fluvial System ◽  
The West ◽  
Drainage Systems ◽  
West Greenland ◽  
Igneous Province ◽  
Davis Strait ◽  
Supplementary Material

The Mesozoic–Cenozoic separation of Greenland and North America produced the small oceanic basins of the Labrador Sea and Baffin Bay, connected via a complex transform system through the Davis Strait. During rifting and partial breakup sedimentary basins formed that record the changing regional sediment supply. The onshore and offshore stratigraphy of Central West Greenland outlines the presence of a major fluvial system that existed during the Cretaceous and was later redirected in the Early Cenozoic by the formation of the West Greenland Igneous Province. Hydrological analysis of Greenland's isostatically balanced basement topography outlines two major drainage systems that likely flowed across Greenland prior to the onset of glaciation and emptied into the Sisimiut Basin within the Davis Strait, offshore West Greenland. The course of the northern drainage system suggests that it initially flowed NW into the Cretaceous/Palaeocene Nuussuaq Basin, before being redirected SW around the West Greenland Igneous Province in the Mid-Palaeocene. Moreover, characteristics of these two drainage systems suggest they acted as a single larger fluvial system, prior to the onset of glaciation, that was likely the primary source of sediment across Central West Greenland throughout the Cretaceous and Palaeogene. This scenario provides a greater understanding of the West Greenland margin's late Cenozoic evolution, which differs from previous interpretations that hypothesize a period of considerable post-rift tectonism and uplift. This work highlights the importance of large pre-glacial drainage systems across North Atlantic passive margins and their relevance when studying post-rift stratigraphy in rifted margin settings.Supplementary material: Isostatic modelling, hydrological analysis and chi mapping is available at: https://doi.org/10.6084/m9.figshare.c.5050146

scholarly journals Correlation between tectonic stress regimes and methane seepage on the western Svalbard margin

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 79-94 ◽  
Author(s):  
Andreia Plaza-Faverola ◽  
Marie Keiding
Keyword(s):  
Gas Hydrate ◽  
Surface Deformation ◽  
Tectonic Stress ◽  
Maximum Principal Stress ◽  
Stress Regime ◽  
Near Surface ◽  
Ocean Ridges ◽  
Methane Seepage ◽  
Lithospheric Flexure ◽  
State Of Stress

Abstract. Methane seepage occurs across the western Svalbard margin at water depths ranging from < 300 m, landward from the shelf break, to > 1000 m in regions just a few kilometres from the mid-ocean ridges in the Fram Strait. The mechanisms controlling seepage remain elusive. The Vestnesa sedimentary ridge, located on oceanic crust at a depth of 1000–1700 m, hosts a perennial gas hydrate and associated free gas system. The restriction of the occurrence of acoustic flares to the eastern segment of the sedimentary ridge, despite the presence of pockmarks along the entire ridge, indicates a spatial variation in seepage activity. This variation coincides with a change in the faulting pattern as well as in the characteristics of the fluid flow features. Due to the position of the Vestnesa Ridge with respect to the Molloy and Knipovich mid-ocean ridges, it has been suggested that seepage along the ridge has a tectonic control. We modelled the tectonic stress regime due to oblique spreading along the Molloy and Knipovich ridges to investigate whether spatial variations in the tectonic regime along the Vestnesa Ridge are plausible. The model predicts a zone of tensile stress that extends northward from the Knipovich Ridge and encompasses the zone of acoustic flares on the eastern Vestnesa Ridge. In this zone the orientation of the maximum principal stress is parallel to pre-existing faults. The model predicts a strike-slip stress regime in regions with pockmarks where acoustic flares have not been documented. If a certain degree of coupling is assumed between deep crustal and near-surface deformation, it is possible that ridge-push forces have influenced seepage activity in the region by interacting with the pore-pressure regime at the base of the gas hydrate stability zone. More abundant seepage on the eastern Vestnesa Ridge at present may be facilitated by the dilation of faults and fractures favourably oriented with respect to the stress field. A modified state of stress in the past, due to more significant glacial stress for instance, may explain vigorous seepage activity along the entire Vestnesa Ridge. The contribution of other mechanisms to the state of stress (i.e. sedimentary loading and lithospheric flexure) remain to be investigated. Our study provides a first-order assessment of how tectonic stresses may be influencing the kinematics of near-surface faults and associated seepage activity offshore of the western Svalbard margin.

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