Crustal Structure in the Vøring Basin, Northern Norway, from Three-Component Ocean Bottom Seismographs

Mjelde, Rolf; Kodaira, Shuichi; Shimamura, Hideki; Shiobara, Hajime; Kanazawa, Toshihiko; Berg, Eivind

doi:10.3997/2214-4609.201409218

Cited by 7 publications

(25 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A regional study performed along lines where high-quality multichannel reflection profiles had already been acquired (MJELDE et al, 1995b), a semi-regional study consisting of twenty-five OBSs with 1.5 -8 km spacing along a 120-km long profile (line 7, Fig. 1), as well as two more detailed experiments (MJELDE et al, 1995a).…”

Section: Data Acquisition and Processingmentioning

confidence: 99%

See 1 more Smart Citation

Comparison between a Regional and Semi-regional Crustal OBS Model in the Vøring Basin, Mid-Norway Margin

Mjelde

Kodaira

Digranes

et al. 1997

Pure appl. geophys.

Self Cite

View full text Add to dashboard Cite

Semi-regional Ocean Bottom Seismograph (OBS) data acquired in the central and northern part of the Vo *ring Basin, mid-Norway margin, have been modeled by use of 2-D ray-tracing. The semi-regional model, derived from the study of twenty-five OBSs deployed along a 120-km long profile, is compared with a regional model consisting of five OBSs from the same profile. The semi-regional model is somewhat more detailed than the regional model, due to the considerably closer receiver spacing. The overall geometry and velocity distribution of the two models are remarkably similar, however, proving that the regional procedure with large OBS spacing provides a reliable regional model.Intrusions of sills, related to early Tertiary continental rifting and break up, are important at intermediate and deep sedimentary levels (2 -10 km below sea floor) in most parts of the area. The semi-regional modeling suggests that one of the deepest sills extends much further east and is substantially thicker (locally more than 500 m) than indicated in the regional model. Another important difference is a high-velocity body within the upper crystalline crust at 11 -12 km depth in the NW part of the area, indicating that the closer OBS spacing in the semi-regional modeling allows detection of local intra-crustal intrusions. Local differences are also inferred in the lower crust; at about 20 km depth a structure is inferred within the lower crust from wide-angle reflections. This might suggest that the high-velocity lower crustal layer, interpreted as magmatic underplating, consists of a mixture of underplated/intruded magmatic material and blocks of continental lower crust.

show abstract

Section: Data Acquisition and Processingmentioning

confidence: 99%

“…The area from the end of the profile to the hatched lines had no ray coverage during the survey. From Mjelde et al (1995b).…”

Section: Figurementioning

confidence: 99%

Comparison between a Regional and Semi-regional Crustal OBS Model in the Vøring Basin, Mid-Norway Margin

Mjelde

Kodaira

Digranes

et al. 1997

Pure appl. geophys.

Self Cite

View full text Add to dashboard Cite

show abstract

“…However, owing to large uncertainties in such amplitude modeling [Mjelde et al, 1997] we considered only the overall character of the amplitude variations with offset by visual comparison. We paid special attention to the following two features which are not considered during the travel time inversion: the range of distances over which each refraction phase was observed and the location of the critical point of the reflection phases.…”

Section: Modeling Proceduresmentioning

confidence: 99%

Western Nankai Trough seismogenic zone: Results from a wide‐angle ocean bottom seismic survey

Kodaira¹,

Takahashi²,

Park³

et al. 2000

J. Geophys. Res.

104

113

View full text Add to dashboard Cite

Abstract. The Nankai Trough, southwestern Japan, is recognized as a vigorous seismogenic zone with well-studied historic earthquakes. This paper presents results of a wide-angle ocean bottom seismographs (OBS) study at the western Nankai Trough seismogenic zone. The OBS data used were acquired on a profile (250 km long) across the presumed coseismic slip zone of the 1946 Nankaido earthquake (Ms=8.2). The main purpose of the seismic study is to obtain an entire crustal cross section of the seismogenic zone for the 1946 earthquake. The crustal model is characterized by a gentle sloping of subducting oceanic crust and thick overlying sedimentary wedge. P wave seismic velocities of the subducting oceanic crust show normal oceanic crustal velocities (Vp=5.0-5.6 km/s and 6.6-6.8 km/s in oceanic layers 2 and 3, respectively). The maximum thickness of the sedimentary wedge is 9 km at 70 km from the trough axis with Vp=3.4-4.6 km/s in the deeper part. The subducting oceanic crust traced down to 25 km depth shows that the subduction angle becomes steeper landward: 3.2øand 7.2 ø at 0-50 km and 50-100 km from the trough axis, respectively. The oceanic crust is smooth to the hypocenter zone, down to 40 km depth beneath Shikoku Island. Our crustal model shows that the downdip limit of the coseismic slip area does not extend to the deep end of the oceanic crust-island arc crust contact zone. Even though there is large uncertainty about the seaward limit of the coseismic slip zone, the crustal model clearly indicates that the updip limit of the coseismic slip zone extends beneath the young accretionary prism.

show abstract

“…This first simple stack (Fig. 8) showed the major horizons and a dipping event interpreted as the intra Campanian unconformity (Mjelde et al, 1997a) located above the flatspot, which cannot be seen clearly.…”

Section: Processing Of the Vertical Componentmentioning

confidence: 99%

“…1). The data acquisition program consisted of three parts, with one regional and one semi-regional part providing the large basin coverage (Digranes et al, 1996;Mjelde et al, 1996Mjelde et al, , 1997a. The third part consisted of a local survey with 20 OBSs dropped along surface seismic line VB-08-89 at approximately 200 m interval in 1300 m water depth (Fig.…”

Section: Introductionmentioning

confidence: 99%

Three-component OBS-data processing for lithology and fluid prediction in the mid-Norway margin, NE Atlantic

et al. 2014

View full text Add to dashboard Cite

In 1992, a comprehensive three-component ocean bottom seismic survey was performed in the central and northern area of the Vøring Basin, offshore mid-Norway, NE Atlantic. An important part of the data acquisition program consisted of a local survey with 20 Ocean Bottom Seismographs (OBS) dropped at approximately 200 m interval in 1300 m water depth. The main purpose of the local survey was to acquire densely sampled P-and S-wave reflection data above a seismic flatspot anomaly observed earlier, in order to more accurately predict if hydrocarbons could be related to it. The conventional reflection data processing methods applied to the vertical components included predictive deconvolution in order to attenuate low frequency ringing, near offset mute and a series of constant velocity stacks in order to obtain the optimal velocity function. The final result is a "trouser" shaped, high resolution V z stacked section with minor influence of water multiples. The inline (V x ) component contains no strong multiples, and extensive near trace muting was hence not necessary to apply for this component. Velocity analysis together with ray-tracing modelling indicate that P-S-converted shear waves (reflections) represent the dominant mode. The results of the interpretation and modelling indicated a V p /V s -ratio of approximately 2.6 in the overburden, which suggests domination of partly unconsolidated shale, while the V p /V s -ratio in the assumed reservoir was approximately 1.8, which indicates a more sand dominated facies. Outside the flatspot area a higher V p /V s -ratio ratio (approximately 2.0) was estimated, indicating that hydrocarbons could be present in the assumed reservoir.

show abstract

Crustal Structure in the Vøring Basin, Northern Norway, from Three-Component Ocean Bottom Seismographs

Cited by 7 publications

References 0 publications

Comparison between a Regional and Semi-regional Crustal OBS Model in the Vøring Basin, Mid-Norway Margin

Comparison between a Regional and Semi-regional Crustal OBS Model in the Vøring Basin, Mid-Norway Margin

Western Nankai Trough seismogenic zone: Results from a wide‐angle ocean bottom seismic survey

Three-component OBS-data processing for lithology and fluid prediction in the mid-Norway margin, NE Atlantic

Contact Info

Product

Resources

About