Seismoacoustic Study of the Shallow Gas Transport and ... - E-LIB

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Chapter 1 Submarine gas seeps, pockmarks and mud volcanoes on land and the seafloor seem to be the largest geologic methane sources. Among them, mud volcanoes can be the most important source of methane with other hydrocarbon and non-hydrocarbon gases to the atmosphere and the ocean. The global methane flux from mud volcanoes nearly equals the global gas flux (Milkov et al., 2003; Etiope and Milkov, 2004). Figure 4 Summary of methane-related seabed fluid seepage structures, such as gas seeps, mud volcanoes and pockmarks, and the process of methane release from marine sediments to the atmosphere (after Whelan et al., 2005). The influence of methane from seabed fluid seepage on climate change is not only confined to the modern climate, but also can influence the paleo-climate. According to methane from mud volcanoes alone can generate deep effects on the Earth’s climate since the Paleozoic (570 Ma) (Kopf, 2003). A close relationship between global temperature and atmospheric methane concentrations was proved in ice cores from Greenland (over a 40 000 year period; Chappellaz et al., 1993) and Antarctica (over 150 000 years; Jouzel et al., 1993), which suggests a link between methane emissions and the Quaternary glacialinterglacial cycles (Judd et al., 2002a). Moreover, massive methane emission is considered to be responsible for paleo-warming events (Luyendyk et al. 2005; Kennett et al., 2003; Nisbet, 2002), or even mass extinctions (Ryskin, 2003). 9
Chapter 1 1.2.1.2 Geological processes Gases, fluid and gas hydrates within marine sediments can influence the geopressure and physical properties, which are considered the significant factors which shape the morphology of continental margins and the deep-sea basins, and which cause marine geohazards (Fig. 5). Different types of seabed morphologies associated with seabed gas/fluid flow include seeps, pockmarks and mud volcanoes, which will be introduced in details in the following sections. Marine geohazards can be divided into two aspects, one is those associated with natural features and events (slope failures, seismicity, mud volcano eruptions, etc.); the other is those that occur as a result of human’s intervention with the natural seabed environment (Judd and Hovland, 2007) (blowouts, such as Gulf of Mexico oil spill 2010 ). Figure 5 Schematic diagram shows main marine geohazards, such as slope instability and mass wasting processes, pore pressure phenomena and seismicity. (After http://www.ngi.no/en/Geohazards/Research/ Offshore-Geohazards/). Submarine slope failure can be triggered by many factors, apart from seismicity, active sedimentation and erosion, salt tectonics (McAdoo et al., 2000), also by gas/fluids and gas hydrates. It is the most serious threat of offshore and coastal areas, because it can give rise to tsunamis. Furthermore, mass amounts of methane may be released into hydrosphere and atmosphere when slope failures occur. 1.2.1.3 Benefits Gas- and oil-related seabed fluid seepage can be used to predict the presence of oil and gas fields or gas hydrate fields (Link, 1952; Kutas et al., 2004), and have guided petroleum exploration for centuries. The methods to investigate the seeps including satellite imaging, acoustic surveying, gravity coring and water column chemical sniffers, etc., which are in low cost to conventional exploration methods, and reduce the risk of exploration (Ding, 2008). Judd and Hovland (2007) pointed out that fish productivity could be enhanced in seep areas, such as the offshore part of the Eel River Delta, northern California, and North Sea, 10
Page 1: Seismoacoustic Study of the Shallow
Page 4 and 5: Table of contents Table of contents
Page 6 and 7: Abstract Abstract In recent years,
Page 8 and 9: Outline of the Dissertation Outline
Page 10 and 11: Chapter 1 Chapter 1. Introduction 1
Page 12 and 13: Chapter 1 reflections, interpreted
Page 16 and 17: Chapter 1 which have documented act
Page 18 and 19: Chapter 1 fluid migration related t
Page 20 and 21: Chapter 1 Evidence of gas seepage
Page 22 and 23: Chapter 1 The three main different
Page 24 and 25: Chapter 1 from deeper sources in th
Page 26 and 27: Chapter 1 numerous countries such a
Page 28 and 29: Chapter 1 1.5 Geological setting of
Page 30 and 31: Chapter 1 main sequences consist of
Page 32 and 33: Chapter 1 craterlike depressions wi
Page 34 and 35: Chapter 1 Jurassic - Paleogene, Upp
Page 36 and 37: Chapter 1 respectively, and one wat
Page 38 and 39: Chapter 1 During the seismic data p
Page 40 and 41: Chapter 1 1.6.2 The Parasound sedim
Page 42 and 43: Chapter 1 Caress, D.W., and Chayes,
Page 44 and 45: Chapter 1 Hovland, M., Gardner, J.V
Page 46 and 47: Chapter 1 Luo, X.R. and Vasseur, G.
Page 48 and 49: Chapter 1 Schroot, B.M., Klaver, G.
Page 50 and 51: Chapter 2 Chapter 2. Shallow Gas Tr
Page 52 and 53: Chapter 2 times. Seismically imaged
Page 54 and 55: Chapter 2 spike noise were marked a
Page 56 and 57: Chapter 2 The 2D high resolution se
Page 58 and 59: Chapter 2 Figure 4 A close-up of se
Page 60 and 61: Chapter 2 within the upper sediment
Page 62 and 63: Chapter 2 volcanoes between 66 and
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Chapter 2 Figure 7 Geo-seismic sect
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Chapter 2 In the study area, many b
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Chapter 2 volcanism could be calcul
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Chapter 2 along the feeder channel
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Chapter 2 Evpatoriya). Soviet Geol
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Chapter 3 Chapter 3. Sedimentary Ev
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Chapter 3 South (Fig. 2). The water
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Chapter 3 Figure 3 (a) Uninterprete
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Chapter 3 Seven seismic facies type
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Chapter 3 Seismic Unit 5 ranges in
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Chapter 3 3.4.3.5. Seismic Unit 2 A
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Chapter 3 Figure 11 (a) Uninterpret
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Chapter 3 Figure 13 (a) Uninterpret
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Chapter 3 boundary between the Plio
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Chapter 3 Seismic Unit 6 belongs to
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Chapter 3 subsidence was coincident
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Chapter 3 Acknowledgements We thank
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Chapter 3 Tugolesov, D.A., Gorshkov
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Chapter 4 study area at ~900 m wate
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Chapter 4 Figure 2 Bathymetry of th
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Chapter 4 University of Bremen). At
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Chapter 4 and Ridge R2 (GeoB07-139)
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Chapter 4 flares location. Anticlin
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Chapter 4 GeoB07-145. Green arrows
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Chapter 4 4.4.3.2.3. Other anomalou
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Chapter 4 Slope fan deposits with f
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Chapter 4 Figure 12 Possible locati
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Chapter 4 bulk hydrate or even high
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Chapter 4 may add to gas accumulati
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Chapter 4 The narrow-beam Parasound
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Chapter 4 River fan deposits. Being
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Chapter 4 Klaucke, I., Sahling, H.,
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Chapter 4 Wagner-Friedrichs, M., 20
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Chapter 5 deposited; during lowstan
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Chapter 5 accumulations. An acousti
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Acknowledgements Acknowledgements I
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