Slowness‐weighted diffraction stack for migrating wide‐angle seismic data in laterally varying media

Geophysics ◽  
2004 ◽  
Vol 69 (4) ◽  
pp. 1046-1052 ◽  
Author(s):  
Harm J. A. Van Avendonk
Keyword(s):  
Seismic Data ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Image Space ◽  
Wide Angle ◽  
Data Set ◽  
Seismic Velocity Structure ◽  
Depth Migration ◽  
Angle Data ◽  
Reflecting Boundaries

Wide‐angle prestack depth migration is an important tool for studying the nature of reflecting boundaries in the earth's crust. The slowness‐weighted diffraction stack (SWDS) method has been used to incorporate both two‐way traveltime constraints and slowness information in the migration. For this purpose, traveltimes and apparent slownesses of reflected arrivals must be calculated in the image space. Earlier applications of SWDS required a 1D or gently varying seismic velocity structure to obtain these quantities by ray tracing in the image space. I show that the apparent slownesses can also be derived directly from one‐way traveltime maps using Fermat's principle. The SDWS is applied to an existing onshore–offshore wide‐angle data set, and the example shows that the method can be used to image detailed reflectivity structure at great depths.

scholarly journals Last stage of the Japan Sea back-arc opening deduced from the seismic velocity structure using wide-angle data

2006 ◽  
Vol 7 (6) ◽  
pp. n/a-n/a ◽  
Author(s):  
Takeshi Sato ◽  
Narumi Takahashi ◽  
Seiichi Miura ◽  
Gou Fujie ◽  
Dong-Hyo Kang ◽  
...  
Keyword(s):  
Velocity Structure ◽  
Seismic Velocity ◽  
Japan Sea ◽  
Wide Angle ◽  
Seismic Velocity Structure ◽  
Angle Data ◽  
The Japan Sea ◽  
Last Stage ◽  
Back Arc

Shifted-elliptical nonstretch moveout correction of wide-angle seismic data in the τ-p domain, using an example from the Faeroe-Shetland Basin

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. B227-B236 ◽  
Author(s):  
Hassan Masoomzadeh ◽  
Satish C. Singh ◽  
Penny J. Barton
Keyword(s):  
Seismic Data ◽  
Seismic Reflection ◽  
Wide Angle ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Angle Data ◽  
Vertical Heterogeneity ◽  
P Domain

We developed a method of moveout correction in the [Formula: see text] domain to tackle some of the problems associated with processing wide-angle seismic reflection data, including residual moveout and normal-moveout stretching. We evaluated the concept of the shifted ellipse in the [Formula: see text] domain as an alternative to the well-known concept of the shifted hyperbola in the [Formula: see text] domain. We used this shifted-ellipse concept to address the problem of residual moveout caused by vertical heterogeneity in the subsurface. We also addressed the stretching problem associated with dynamic corrections by combining selected strips from a set of constant-moveout stacks generated using a shifted-ellipse equation. Application of this method to a wide-angle data set from the Faeroe-Shetland Basin provided an enhanced image of the subbasalt structure.

Depth migration before stack

Geophysics ◽  
1980 ◽  
Vol 45 (3) ◽  
pp. 376-393 ◽  
Author(s):  
Philip S. Schultz ◽  
John W. C. Sherwood
Keyword(s):  
Seismic Data ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Signal Amplitude ◽  
Scalar Wave ◽  
Lateral Velocity ◽  
Seismic Section ◽  
Depth Migration ◽  
Velocity Gradients ◽  
Zero Offset

When seismic data are migrated using operators derived from the scalar wave equation, an assumption is normally made that the seismic velocity in the propagating medium is locally laterally invariant. This simplifying assumption causes reflectors to be imaged incorrectly when lateral velocity gradients exist, irrespective of the degree of accuracy to which the subsurface velocity structure is known. A finite‐difference method has been implemented for migration of unstacked data in the presence of lateral velocity gradients, where the operation of wave field extrapolation is done in increments of depth rather than time. Performing this depth migration on unstacked data results in the imaging of reflectors on the zero‐offset trace, whereupon a zero‐offset section becomes a fully imaged‐in‐depth seismic section. Such a section, in addition to being a correctly migrated depth section, shows the same order of signal amplitude enhancement as in a normal stacking process.

scholarly journals Seismic velocity structure at the southern termination of the 2016 Kumamoto Earthquake rupture, Japan

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Yasuhira Aoyagi ◽  
Haruo Kimura ◽  
Kazuo Mizoguchi
Keyword(s):  
Fault Zone ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
Earthquake Rupture ◽  
2016 Kumamoto Earthquake ◽  
Seismic Velocity Structure ◽  
Kumamoto Earthquake ◽  
Seismogenic Layer ◽  
The 2016 Kumamoto Earthquake ◽  
Tectonic Line

Abstract The earthquake rupture termination mechanism and size of the ruptured area are crucial parameters for earthquake magnitude estimations and seismic hazard assessments. The 2016 Mw 7.0 Kumamoto Earthquake, central Kyushu, Japan, ruptured a 34-km-long area along previously recognized active faults, eastern part of the Futagawa fault zone and northernmost part of the Hinagu fault zone. Many researchers have suggested that a magma chamber under Aso Volcano terminated the eastward rupture. However, the termination mechanism of the southward rupture has remained unclear. Here, we conduct a local seismic tomographic inversion using a dense temporary seismic network to detail the seismic velocity structure around the southern termination of the rupture. The compressional-wave velocity (Vp) results and compressional- to shear-wave velocity (Vp/Vs) structure indicate several E–W- and ENE–WSW-trending zonal anomalies in the upper to middle crust. These zonal anomalies may reflect regional geological structures that follow the same trends as the Oita–Kumamoto Tectonic Line and Usuki–Yatsushiro Tectonic Line. While the 2016 Kumamoto Earthquake rupture mainly propagated through a low-Vp/Vs area (1.62–1.74) along the Hinagu fault zone, the southern termination of the earthquake at the focal depth of the mainshock is adjacent to a 3-km-diameter high-Vp/Vs body. There is a rapid 5-km step in the depth of the seismogenic layer across the E–W-trending velocity boundary between the low- and high-Vp/Vs areas that corresponds well with the Rokkoku Tectonic Line; this geological boundary is the likely cause of the dislocation of the seismogenic layer because it is intruded by serpentinite veins. A possible factor in the southern rupture termination of the 2016 Kumamoto Earthquake is the existence of a high-Vp/Vs body in the direction of southern rupture propagation. The provided details of this inhomogeneous barrier, which are inferred from the seismic velocity structures, may improve future seismic hazard assessments for a complex fault system composed of multiple segments.

Seismic tomographic interpretation of Paleozoic sedimentary sequences in the southeastern North Sea

Geophysics ◽  
2005 ◽  
Vol 70 (4) ◽  
pp. R45-R56 ◽  
Author(s):  
Lars Nielsen ◽  
Hans Thybo ◽  
Martin Glendrup
Keyword(s):  
North Sea ◽  
Velocity Structure ◽  
Seismic Velocity ◽  
P Wave ◽  
Wide Angle ◽  
North German Basin ◽  
Sedimentary Sequences ◽  
The North ◽  
Crystalline Crust ◽  
German Basin

Seismic wide-angle data were recorded to more than 300-km offset from powerful airgun sources during the MONA LISA experiments in 1993 and 1995 to determine the seismic-velocity structure of the crust and uppermost mantle along three lines in the southeastern North Sea with a total length of 850 km. We use the first arrivals observed out to an offset of 90 km to obtain high-resolution models of the velocity structure of the sedimentary layers and the upper part of the crystalline crust. Seismic tomographic traveltime inversion reveals 2–8-km-thick Paleozoic sedimentary sequences with P-wave velocities of 4.5–5.2 km/s. These sedimentary rocks are situated below a Mesozoic-Cenozoic sequence with variable thickness: ∼2–3 km on the basement highs, ∼2–4 km in the Horn Graben and the North German Basin, and ∼6–7 km in the Central Graben. The thicknesses of the Paleozoic sedimentary sequences are ∼3–5 km in the Central Graben, more than 4 km in the Horn Graben, up to ∼4 km on the basement highs, and up to 8 km in the North German Basin. The Paleozoic strata are clearly separated from the shallower and younger sequences with velocities of ∼1.8–3.8 km/s and the deeper crystalline crust with velocities of more than 5.8–6.0 km/s in the tomographic P-wave velocity model. Resolution tests show that the existence of the Paleozoic sediments is well constrained by the data. Hence, our wide-angle seismic models document the presence of Paleozoic sediments throughout the southeastern North Sea, both in the graben structures and in deep basins on the basement highs.

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