scholarly journals Reflection seismic studies over the end-glacial Burträsk fault, Skellefteå, Sweden

2010 ◽  
Vol 2 (2) ◽  
pp. 307-329 ◽  
Author(s):  
C. Juhlin ◽  
B. Lund
Keyword(s):  
Fracture Zone ◽  
Seismic Data ◽  
Mafic Rock ◽  
Seismic Profile ◽  
Large Displacements ◽  
Fault Geometry ◽  
Seismic Section ◽  
Glacial Ice ◽  
Crustal Rocks ◽  
Reflection Seismic

Abstract. Reflection seismic data were acquired along a ca. 22 km long profile over the end-glacial Burträsk Fault with a nominal receiver and source spacing of 20 m. A steeply dipping reflection can be correlated to the Burträsk Fault, indicating that the fault dips at about 55° to the southeast near the surface. The reflection from the fault is rather poorly imaged, probably due to a jump in the fault and the crookedness of the seismic profile in the vicinity of the fault. A more pronounced steeply dipping reflection is observed about 4 km southeast of the Burträsk Fault. Based on its correlation with a topographic low at the surface this reflection is interpreted to originate from a fracture zone. There are no signs of large displacements along this fault as the glacial ice receded, but it may be active today. Other reflections on the processed seismic section may originate from changes in lithological variations in the supra-crustal rocks or from intrusions of more mafic rock. Constraints on the fault geometry provided by the reflection seismic data will help determine what stresses were required to activate the fault when the major rupture along it occurred.

scholarly journals Reflection seismic studies over the end-glacial Burträsk fault, Skellefteå, Sweden

Solid Earth ◽  
2011 ◽  
Vol 2 (1) ◽  
pp. 9-16 ◽  
Author(s):  
C. Juhlin ◽  
B. Lund
Keyword(s):  
Seismic Data ◽  
Mafic Rock ◽  
Seismic Profile ◽  
Large Displacements ◽  
Fault Geometry ◽  
Seismic Section ◽  
Glacial Ice ◽  
Crustal Rocks ◽  
Reflection Seismic ◽  
Lateral Offset

Abstract. Reflection seismic data were acquired along a ca. 22 km long profile over the end-glacial Burträsk fault with a nominal receiver and source spacing of 20 m. A steeply dipping reflection can be correlated to the Burträsk fault, indicating that the fault dips at about 55° to the southeast near the surface. The reflection from the fault is rather poorly imaged, probably due to a lateral offset in the fault of about 1 km at this location and the crookedness of the seismic profile in the vicinity of the fault. A more pronounced steeply dipping reflection is observed about 4 km southeast of the Burträsk fault. Based on its correlation with a topographic low at the surface this reflection is interpreted to originate from a fracture zone. There are no signs of large displacements along this zone as the glacial ice receded, but earthquakes could be associated with it today. Other reflections on the processed seismic section may originate from changes in lithological variations in the supra-crustal rocks or from intrusions of more mafic rock. Constraints on the fault geometry provided by the reflection seismic data will help determine what stresses were required to activate the fault when the major rupture along it occurred ca. 9500 years ago.

Vertical resolution of a seismic survey in stratigraphic sequences less than 100 m deep in southeastern Kansas

Geophysics ◽  
1995 ◽  
Vol 60 (2) ◽  
pp. 423-430 ◽  
Author(s):  
Richard D. Miller ◽  
Neil L. Anderson ◽  
Howard R. Feldman ◽  
Evan K. Franseen
Keyword(s):  
Seismic Data ◽  
Fresnel Zone ◽  
Drill Hole ◽  
Seismic Profile ◽  
Dominant Frequency ◽  
Seismic Survey ◽  
Vertical Resolution ◽  
Resolution Limit ◽  
Reflection Seismic ◽  
Quarter Wavelength

A 400-m long, 12‐fold high‐resolution common depth point (CDP) reflection seismic profile was acquired across shallow converging Pennsylvanian strata in the Independence area of southeastern Kansas. One of the principal objectives was to determine practical vertical resolution limits in an excellent shallow seismic‐data area with borehole control. The dominant frequency of the CDP stacked data is in excess of 150 Hz based on peak‐to‐peak measurements. Interference phenomena observed on stacked seismic data incorporated with models derived from log and drill‐hole information suggest a practical vertical resolution limit of about 7 m, or one‐third of the dominant wavelength. This practical resolution is slightly less than the predicted (theoretical) resolution limit of 5 m based on the generally accepted one‐quarter wavelength axiom. These data suggest conventional rules of thumb describing resolution potential are not accurate when reflectors on shallow, narrow bandwidth data converge rapidly across horizontal distances less than the Fresnel Zone.

scholarly journals Wrench-fault structures superimposed by glaciotectonic complexes, interpreted from high-resolution reflection-seismic sections and boreholes along the western bank of Esrum Sø, north-east Sjælland, Denmark

2020 ◽  
Vol 68 ◽  
pp. 171-193
Author(s):  
Line Bayer Winslow ◽  
Stig A. Schack pedersen ◽  
Lars Ole Boldreel ◽  
Egon Nørmark
Keyword(s):  
Seismic Profile ◽  
Seismic Section ◽  
Reflection Seismic ◽  
North East ◽  
Structural Framework ◽  
Scandinavian Ice Sheet ◽  
Fault Structures ◽  
Seismic Sections ◽  
Wrench Fault ◽  
Flower Structures

Wrench-fault structures below Danian limestone and Palaeogene marl, and an overlying structural framework of Quaternary glacial deposits in north-east Sjælland, Denmark, are interpreted from two vibro-seismic sections recorded to 600 msec TWT depth. The main seismic section is 6.3 km long, N–S oriented, and intersected by a 0.7 km long, E–W oriented satellite seismic section. In addition, boreholes in the vicinity of the seismic profile are used for the interpretation. The sections were acquired in 2014 along the western shoreline of the lake Esrum Sø in the Gribskov area. In the lower part of the seismic section (the interval 100–300 msec TWT), parallel-bedded geological layers occur along most of the profile apart from six locations, where six wrench-fault structures displace the upper part of the Chalk Group and lower Palaeogene marl. The northernmost of the six wrench-fault locations correlates to the eastern slope of the buried Esrum–Alnarp valley, which suggests that the valley is an inherited tectonic feature. The location of the wrench- fault structures supports the outline of faults related to the Sorgenfrei-Tornquist Zone on previous geological maps, which had almost no seismic data from the area. Above the stratigraphic level presented by the Danian limestone and lower Palaeogene marl, a composite glaciotectonic complex comprising two glaciodynamic sequences is recognized by e.g. thrust-fault structures and the lithostratigraphy of glacial successions recorded in the wells. In parts of the seismic sections, the lowermost level of the glaciotectonic complex inherited the wrench-tectonic fault structures, most significantly seen in the northern segment. The advance of the Scandinavian ice sheet caused the glaciotectonic structures displayed in the seismic section. The two sequences represent events related to the Norwegian and the Swedish glacial advances. From the interpretation of the seismic section it is found that the glaciotectonic complex conceals the wrench-tectonic flower structures.

Constraints on Reelfoot Rift Evolution from a Reflection Seismic Profile in the Northern Rift

1992 ◽  
Vol 63 (3) ◽  
pp. 233-241 ◽  
Author(s):  
M.B. Goldhaber ◽  
C.J. Potter ◽  
C.D. Taylor
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Seismic Profile ◽  
Fault System ◽  
Seismic Reflection Profile ◽  
The South ◽  
Dome A ◽  
Reflection Seismic ◽  
The North ◽  
Northwestern Margin

Abstract An 82.8 km segment of a northwest-southeast trending seismic-reflection profile across the northernmost part of the Reelfoot rift shows that the Cambrian rift geometry there is quite distinct from that of the main part of Reelfoot rift to the south, and that of the Rough Creek graben to the east. The profile is within the area of intersection of the Reelfoot rift and Rough Creek graben and shows a systematic southeastward thickening of the Cambrian synrift clastic sequence with as much as 1940 meters of section present against the Pennyrile fault system as compared to 970 meters near the Lusk Creek and Shawneetown fault systems, towards the northwestern margin of the rift. This contrasts with the more symmetric rift pattern in the seismically active zone to the south, where the maximum thickness of synrift sediments is along the rift axis, and with an opposite sense of rift asymmetry in the Rough Creek graben, where the synrift sequence thickens to the north against the Rough Creek - Shawneetown fault. Reflection patterns in the vicinity of Hicks dome, a “cryptovolcano”, are consistent with the hypothesis that the dome originated by explosive release of mantle-derived gases associated with alkali volcanism. The seismic data also reveal that the fluorine mineralization in the area is associated with faults that offset basement; this is further evidence that deeply-derived fluids are significant in the geologic evolution of the area.

scholarly journals Fault interpretation in seismic reflection data: an experiment analysing the impact of conceptual model anchoring and vertical exaggeration

Solid Earth ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 1651-1662 ◽  
Author(s):  
Juan Alcalde ◽  
Clare E. Bond ◽  
Gareth Johnson ◽  
Armelle Kloppenburg ◽  
Oriol Ferrer ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Conceptual Models ◽  
Seismic Section ◽  
Seismic Reflection Data ◽  
Reflection Seismic ◽  
Reflection Data ◽  
Interpretation Process ◽  
Fault Interpretation ◽  
The Impact

Abstract. The use of conceptual models is essential in the interpretation of reflection seismic data. It allows interpreters to make geological sense of seismic data, which carries inherent uncertainty. However, conceptual models can create powerful anchors that prevent interpreters from reassessing and adapting their interpretations as part of the interpretation process, which can subsequently lead to flawed or erroneous outcomes. It is therefore critical to understand how conceptual models are generated and applied to reduce unwanted effects in interpretation results. Here we have tested how interpretation of vertically exaggerated seismic data influenced the creation and adoption of the conceptual models of 161 participants in a paper-based interpretation experiment. Participants were asked to interpret a series of faults and a horizon, offset by those faults, in a seismic section. The seismic section was randomly presented to the participants with different horizontal–vertical exaggeration (1:4 or 1:2). Statistical analysis of the results indicates that early anchoring to specific conceptual models had the most impact on interpretation outcome, with the degree of vertical exaggeration having a subdued influence. Three different conceptual models were adopted by participants, constrained by initial observations of the seismic data. Interpreted fault dip angles show no evidence of other constraints (e.g. from the application of accepted fault dip models). Our results provide evidence of biases in interpretation of uncertain geological and geophysical data, including the use of heuristics to form initial conceptual models and anchoring to these models, confirming the need for increased understanding and mitigation of these biases to improve interpretation outcomes.

Density‐based reflectivity in seismic exploration for coal in Alberta, Canada

Geophysics ◽  
1991 ◽  
Vol 56 (1) ◽  
pp. 139-141 ◽  
Author(s):  
D. C. Lawton ◽  
H. V. Lyatsky
Keyword(s):  
Seismic Data ◽  
Compressional Wave ◽  
Seismic Exploration ◽  
Coal Field ◽  
Compressional Wave Velocity ◽  
Coal Seams ◽  
Seismic Section ◽  
Reflection Seismic ◽  
Sonic Logs ◽  
Different Parts

At a coal field in central Alberta, Canada, the acoustic reflectivity of shallow coal seams was found to be dominated by the density contrast between coal and host bentonitic sediments. Sonic logs and a check‐shot survey showed that the compressional‐wave velocity is almost constant through the coal zone and the overlying sediments, and ranges in value between 2000 m/s and 2350 m/s over different parts of the coal field. The average coal density is [Formula: see text], whereas the density of the sediments is about [Formula: see text]. Results are illustrated using logs from a typical drillhole in the coal field. At this location, the time reflectivity sequence based on both the density and sonic logs is very similar to that obtained when the density log only is used, with a constant velocity assumed through the coal zone. At another drillhole location in the coal field, where reflection seismic data had been acquired, a synthetic seismogram generated from the density log closely matches the stacked seismic section.

VIBROSEIS DOWN THE HOLE

1983 ◽  
Vol 23 (1) ◽  
pp. 203
Author(s):  
J. T. Frazer
Keyword(s):  
Seismic Data ◽  
Seismic Source ◽  
Seismic Signal ◽  
Structure Mapping ◽  
Time Duration ◽  
Seismic Section ◽  
Reflection Seismic ◽  
The Past ◽  
Field Estimation ◽  
Seismic Reflections

A variety of problems associated with the Vibroseis® source have been encountered over the past few years which have presented difficulties in tieing surveys using different control systems and in depth mapping.Accurate depth structure mapping and field estimation from seismic data requires good correlation of seismic reflections with stratigraphic boundaries. The information required, a known seismic signal and vertical rock velocities can only be obtained from measurements down the hole.Seismic time to depth correlation can be obtained from an integrated sonic velocity curve tied to conventional well shoot data only if the source is the same as that used for the reflection seismic data or the relation between the well shoot and seismic source is known. It has been apparent for some time that the signal from the Vibroseis source has not been adequately defined from surface measurements.A number of parameters must be monitored to ensure that the signal transmitted during a Vibroseis sweep is properly calibrated. The synchronisation of phase, time duration of the sweep, sweep bandwidth, vibrator drive levels and the phase relation of the pilot sweep to the signal transmitted from the baseplate, contribute to determine the character of the signal seen on a seismic section.®Trademark of Conoco, Inc.

scholarly journals Fault interpretation in a vertically exaggerated seismic section: evidence of conceptual model uncertainty and anchoring

2019 ◽  
Author(s):  
Juan Alcalde ◽  
Clare E. Bond ◽  
Gareth Johnson ◽  
Armelle Kloppenburg ◽  
Oriol Ferrer ◽  
...  
Keyword(s):  
Statistical Analysis ◽  
Conceptual Model ◽  
Seismic Data ◽  
Model Uncertainty ◽  
Conceptual Models ◽  
Geophysical Data ◽  
Seismic Section ◽  
Reflection Seismic ◽  
Interpretation Process ◽  
Fault Interpretation

Abstract. The use of conceptual models is essential in the interpretation of reflection seismic data. It allows interpreters to make geological sense of seismic data which carries inherent uncertainty. However, conceptual models can create powerful anchors that prevent interpreters from reassessing and adapting their interpretations as part of the interpretation process, which can subsequently lead to flawed or erroneous outcomes. It is therefore critical to understand how conceptual models are generated and applied to reduce unwanted effects in interpretation results. Here we have tested how interpretation of vertically exaggerated seismic data influenced the creation and adoption of the conceptual models of 160 participants in a paper-based interpretation experiment. Participants were asked to interpret a series of faults and a horizon, off-set by those faults, in a seismic section. The seismic section was randomly presented to the participants with different horizontal-vertical exaggeration (1 : 4 or 1 : 2). Statistical analysis of the results indicates that early anchoring to specific conceptual models had the most impact on interpretation outcome; with the degree of vertical exaggeration having a subdued influence. Three different conceptual models were adopted by participants, constrained by initial observations of the seismic data. Interpreted fault dip angles show no evidence of other constraint (e.g. from the application of accepted fault dip models). Our results provide evidence of biases in interpretation of uncertain geological and geophysical data, including the use of heuristics to form initial conceptual models and anchoring to these models, confirming the need for increased understanding and mitigation of these biases to improve interpretation outcomes.

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