Inversion of seismic reflection data in the acoustic approximation

Geophysics ◽  
1984 ◽  
Vol 49 (8) ◽  
pp. 1259-1266 ◽  
Author(s):  
Albert Tarantola
Keyword(s):  
Inverse Problem ◽  
Bulk Modulus ◽  
Iterative Algorithm ◽  
Seismic Reflection ◽  
Current Model ◽  
Generalized Least Squares ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Acoustic Approximation

The nonlinear inverse problem for seismic reflection data is solved in the acoustic approximation. The method is based on the generalized least‐squares criterion, and it can handle errors in the data set and a priori information on the model. Multiply reflected energy is naturally taken into account, as well as refracted energy or surface waves. The inverse problem can be solved using an iterative algorithm which gives, at each iteration, updated values of bulk modulus, density, and time source function. Each step of the iterative algorithm essentially consists of a forward propagation of the actual sources in the current model and a forward propagation (backward in time) of the data residuals. The correlation at each point of the space of the two fields thus obtained yields the corrections of the bulk modulus and density models. This shows, in particular, that the general solution of the inverse problem can be attained by methods strongly related to the methods of migration of unstacked data, and commercially competitive with them.

Shallow seismic reflection study of a glaciated valley

Geophysics ◽  
1998 ◽  
Vol 63 (4) ◽  
pp. 1395-1407 ◽  
Author(s):  
Frank Büker ◽  
Alan G. Green ◽  
Heinrich Horstmeyer
Keyword(s):  
Seismic Reflection ◽  
High Amplitude ◽  
Data Sets ◽  
Seismic Section ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Northern Switzerland ◽  
Reflection Data ◽  
Shallow Seismic ◽  
Glaciated Valley

Shallow seismic reflection data were recorded along two long (>1.6 km) intersecting profiles in the glaciated Suhre Valley of northern Switzerland. Appropriate choice of source and receiver parameters resulted in a high‐fold (36–48) data set with common midpoints every 1.25 m. As for many shallow seismic reflection data sets, upper portions of the shot gathers were contaminated with high‐amplitude, source‐generated noise (e.g., direct, refracted, guided, surface, and airwaves). Spectral balancing was effective in significantly increasing the strength of the reflected signals relative to the source‐generated noise, and application of carefully selected top mutes ensured guided phases were not misprocessed and misinterpreted as reflections. Resultant processed sections were characterized by distributions of distinct seismic reflection patterns or facies that were bounded by quasi‐continuous reflection zones. The uppermost reflection zone at 20 to 50 ms (∼15 to ∼40 m depth) originated from a boundary between glaciolacustrine clays/silts and underlying glacial sands/gravels (till) deposits. Of particular importance was the discovery that the deepest part of the valley floor appeared on the seismic section at traveltimes >180 ms (∼200 m), approximately twice as deep as expected. Constrained by information from boreholes adjacent to the profiles, the various seismic units were interpreted in terms of unconsolidated glacial, glaciofluvial, and glaciolacustrine sediments deposited during two principal phases of glaciation (Riss at >100 000 and Würm at ∼18 000 years before present).

Migration with reduced artifacts from internal multiple reflections

Geophysics ◽  
2020 ◽  
Vol 85 (4) ◽  
pp. A25-A29
Author(s):  
Lele Zhang
Keyword(s):  
Seismic Reflection ◽  
Computational Cost ◽  
Data Sets ◽  
Square Root ◽  
Multiple Reflections ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Recent Developments ◽  
Multiple Elimination

Migration of seismic reflection data leads to artifacts due to the presence of internal multiple reflections. Recent developments have shown that these artifacts can be avoided using Marchenko redatuming or Marchenko multiple elimination. These are powerful concepts, but their implementation comes at a considerable computational cost. We have derived a scheme to image the subsurface of the medium with significantly reduced computational cost and artifacts. This scheme is based on the projected Marchenko equations. The measured reflection response is required as input, and a data set with primary reflections and nonphysical primary reflections is created. Original and retrieved data sets are migrated, and the migration images are multiplied with each other, after which the square root is taken to give the artifact-reduced image. We showed the underlying theory and introduced the effectiveness of this scheme with a 2D numerical example.

Shallow 3D seismic-reflection imaging of fracture zones in crystalline rock

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. B149-B160 ◽  
Author(s):  
Cedric Schmelzbach ◽  
Heinrich Horstmeyer ◽  
Christopher Juhlin
Keyword(s):  
Seismic Reflection ◽  
Crystalline Rock ◽  
Three Dimensions ◽  
Disposal Site ◽  
3D Seismic ◽  
Fracture Zones ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Receiver Array

A limited 3D seismic-reflection data set was used to map fracture zones in crystalline rock for a nuclear waste disposal site study. Seismic-reflection data simultaneously recorded along two roughly perpendicular profiles (1850 and [Formula: see text] long) and with a [Formula: see text] receiver array centered at the intersection of the lines sampled a [Formula: see text] area in three dimensions. High levels of source-generated noise required a processing sequence involving surface-consistent deconvolution, which effectively increased the strength of reflected signals, and a linear [Formula: see text] filtering scheme to suppress any remaining direct [Formula: see text]-wave energy. A flexible-binning scheme significantly balanced and increased the CMP fold, but the offset and azimuth distributions remain irregular; a wide azimuth range and offsets [Formula: see text] are concentrated in the center of the survey area although long offsets [Formula: see text] are only found at the edges of the site. Three-dimensional dip moveout and 3D poststack migration were necessary to image events with conflicting dips up to about 40°. Despite the irregular acquisition geometry and the high level of source-generated noise, we obtained images rich in structural detail. Seven continuous to semicontinuous reflection events were traced through the final data volume to a maximum depth of around [Formula: see text]. Previous 2D seismic-reflection studies and borehole data indicate that fracture zones are the most likely cause of the reflections.

Minimizing field operations in shallow 3‐D seismic reflection surveying

Geophysics ◽  
2001 ◽  
Vol 66 (6) ◽  
pp. 1761-1773 ◽  
Author(s):  
Roman Spitzer ◽  
Alan G. Green ◽  
Frank O. Nitsche
Keyword(s):  
Seismic Reflection ◽  
Cost Effective ◽  
Unconsolidated Sediments ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Northern Switzerland ◽  
Shallow Subsurface ◽  
Reflection Data ◽  
Effective Manner ◽  
Original Survey

By appropriately decimating a comprehensive shallow 3‐D seismic reflection data set recorded across unconsolidated sediments in northern Switzerland, we have investigated the potential and limitations of four different source‐receiver acquisition patterns. For the original survey, more than 12 000 shots and 18 000 receivers deployed on a [Formula: see text] grid resulted in common midpoint (CMP) data with an average fold of ∼40 across a [Formula: see text] area. A principal goal of our investigation was to determine an acquisition strategy capable of producing reliable subsurface images in a more efficient and cost‐effective manner. Field efforts for the four tested acquisition strategies were approximately 50%, 50%, 25%, and 20% of the original effort. All four data subsets were subjected to a common processing sequence. Static corrections, top‐mute functions, and stacking velocities were estimated individually for each subset. Because shallow reflections were difficult to discern on shot and CMP gathers generated with the lowest density acquisition pattern (20% field effort) such that dependable top‐mute functions could not be estimated, data resulting from this acquisition pattern were not processed to completion. Of the three fully processed data subsets, two (50% field effort and 25% field effort) yielded 3‐D migrated images comparable to that derived from the entire data set, whereas the third (50% field effort) resulted in good‐quality images only in the shallow subsurface because of a lack of far‐offset data. On the basis of these results, we concluded that all geological objectives associated with our particular study site, which included mapping complex lithological units and their intervening shallow dipping boundaries, would have been achieved by conducting a 3‐D seismic reflection survey that was 75% less expensive than the original one.

scholarly journals Using Seismic Attributes in seismotectonic research: an application to the Norcia's Mw = 6.5 earthquake (30th October 2016) in Central Italy

2019 ◽  
Author(s):  
Maurizio Ercoli ◽  
Emanuele Forte ◽  
Massimiliano Porreca ◽  
Ramon Carbonell ◽  
Cristina Pauselli ◽  
...  
Keyword(s):  
Seismic Reflection ◽  
Central Italy ◽  
Seismic Attributes ◽  
Seismic Attribute ◽  
Data Set ◽  
Epicentral Zone ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Reflection Data ◽  
Attribute Analysis

Abstract. In seismotectonic studies, seismic reflection data are a powerful tool to unravel the complex deep architecture of active faults. Such tectonic structures are usually mapped at surface through traditional geological surveying whilst seismic reflection data may help to trace their continuation from the near-surface down to hypocentral depth. In this study, we propose the application of the seismic attributes technique, commonly used in seismic reflection exploration by oil industry, to seismotectonic research for the first time. The study area is a geologically complex region of Central Italy, recently struck by a long-lasting seismic sequence including a Mw 6.5 main-shock. A seismic reflection data-set consisting of three vintage seismic profiles, currently the only available across the epicentral zone, constitutes a singular opportunity to attempt a seismic attribute analysis. This analysis resulted in peculiar seismic signatures which generally correlate with the exposed surface geologic features, and also confirming the presence of other debated structures. These results are critical, because provide information also on the relatively deep structural setting, mapping a prominent, high amplitude regional reflector that marks the top basement, interpreted as important rheological boundary. Complex patterns of high-angle discontinuities crossing the reflectors have been also identified. These dipping fabrics are interpreted as the expression of fault zones, belonging to the active normal fault systems responsible for the seismicity of the region. This work demonstrates that seismic attribute analysis, even if used on low-quality vintage 2D data, may contribute to improve the subsurface geological interpretation of areas characterized by high seismic potential.

scholarly journals Time-lapse imaging using 3D ultra-high-frequency marine seismic reflection data

Geophysics ◽  
2020 ◽  
Vol 85 (2) ◽  
pp. P13-P25
Author(s):  
Michael J. Faggetter ◽  
Mark E. Vardy ◽  
Justin K. Dix ◽  
Jonathan M. Bull ◽  
Timothy J. Henstock
Keyword(s):  
High Frequency ◽  
Seismic Reflection ◽  
High Tide ◽  
Time Lapse ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Near Surface ◽  
Ultra High Frequency ◽  
Reflection Data ◽  
Marine Seismic

Time-lapse (4D) seismic imaging is now widely used as a tool to map and interpret changes in deep reservoirs as well as investigate dynamic, shallow hydrological processes in the near surface. However, there are very few examples of time-lapse analysis using ultra-high-frequency (UHF; kHz range) marine seismic reflection data. Exacting requirements for navigation can be prohibitive for acquiring coherent, true-3D volumes. Variable environmental noise can also lead to poor amplitude repeatability and make it difficult to identify differences that are related to real physical changes. Overcoming these challenges opens up a range of potential applications for monitoring the subsurface at decimetric resolution, including geohazards, geologic structures, as well as the bed-level and subsurface response to anthropogenic activities. Navigation postprocessing was incorporated to improve the acquisition and processing workflow for the 3D Chirp subbottom profiler and provide stable, centimeter-level absolute positioning, resulting in well-matched 3D data and mitigating 4D noise for data stacked into [Formula: see text] common-midpoint bins. Within an example 4D data set acquired on the south coast of the UK, interpretable differences are recorded within a shallow gas blanket. Reflections from the top and bottom of a gas pocket are imaged at low tide, whereas at high tide only the upper reflection is imaged. This case study demonstrates the viability of time-lapse UHF 3D seismic reflection for quantitative mapping of decimeter-scale changes within the shallow marine subsurface.

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.

Linearized inversion of multioffset seismic reflection data in the ω-k domain: Depth‐dependent reference medium

Geophysics ◽  
1988 ◽  
Vol 53 (1) ◽  
pp. 50-64 ◽  
Author(s):  
L. T. Ikelle ◽  
J. P. Diet ◽  
A. Tarantola
Keyword(s):  
Inverse Problem ◽  
Linear System ◽  
Seismic Reflection ◽  
Synthetic Seismograms ◽  
Fourier Domain ◽  
Seismic Reflection Data ◽  
Spatial Variables ◽  
Reflection Data ◽  
Reference Medium ◽  
Set Up

The computation of synthetic seismograms can be linearized with respect to a reference medium that issno close to the actual medium. Using a least‐squares formulation, the inverse problem can then be set up as a problem of quadratic optimization. The inverse problem is greatly simplified if the reference medium is symmetric. For a homogeneous reference medium, a rigorous and economic solution can be obtained by Fourier transforming all spatial variables. In particular, the solution can be obtained through an explicit formula that does not require the resolution of any linear system (as is the case when not working in the Fourier domain). However, the assumption of a homogeneous reference medium is generally not realistic. In some situations, the reference medium can be depth‐dependent. It can then be shown that by Fourier transforming time and all spatial variables except depth, the inverse problem also has an elegant and economic solution. If [Formula: see text] is the (unknown) difference between the reference medium and the true (2-D) medium, the Fourier‐transformed solution [Formula: see text] can be obtained by solving, for each value of the horizontal wavenumber [Formula: see text] a linear system whose dimension equals the number of depth samples.

scholarly journals Active deformation evidence in the offshore of western Calabria (southern Tyrrhenian Sea) from ultra-resolution multichannel seismic reflection data: results from the Gulf of Sant'Eufemia

2020 ◽  
Author(s):  
Fabrizio Pepe ◽  
Mor Kanari ◽  
Pierfrancesco Burrato ◽  
Marta Corradino ◽  
Henrique Duarte ◽  
...  
Keyword(s):  
Data Acquisition ◽  
Seismic Reflection ◽  
Fault System ◽  
Tyrrhenian Sea ◽  
Seismic Profiles ◽  
Data Set ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Multichannel Seismic Reflection Data ◽  
Earthquake Potential

<p>An ultra-resolution, multichannel seismic reflection data set was collected during an oceanographic cruise organised in the frame of the “<em>Earthquake Potential of Active Faults using offshore Geological and Morphological Indicators</em>” (EPAF) project, which was founded by the Scientific and Technological Cooperation (Scientific Track 2017) between the Italian Ministry of Foreign Affairs and International Cooperation and the Ministry of Science, Technology and Space of the State of Israel. The data acquisition approach was based on innovative technologies for the offshore imaging of stratigraphy and structures along continental margins with a horizontal and vertical resolution at decimetric scale. In this work, we present the methodology used for the 2D HR-seismic reflection data acquisition and the preliminary interpretation of the data set. The 2D seismic data were acquired onboard the R/V Atlante by using an innovative data acquisition equipment composed by a dual-sources Sparker system and one HR 48-channel, slant streamers, with group spacing variable from 1 to 2 meters, at 10 kHz sampling rate. An innovative navigation system was used to perform all necessary computations to determining real-time positions of sources and receivers. The resolution of the seismic profiles obtained from this experiment is remarkable high respect to previously acquired seismic data for both scientific and industrial purposes. In addition to the seismic imaging, gravity core data were also collected for sedimentological analysis and to give a chronological constraint using radiocarbon datings to the shallower reflectors. The investigated area is located in the western offshore sector of the Calabrian Arc (southern Tyrrhenian Sea) where previous research works, based on multichannel seismic profiles coupled with Chirp profiles, have documented the presence of an active fault system. One of the identified faults was tentatively considered as the source of the Mw 7, 8 September 1905 seismic event that hit with highest macroseismic intensities the western part of central Calabria, and was followed by a tsunami that inundated the coastline between Capo Vaticano and the Angitola plain. On this basis, the earthquake was considered to have a source at sea, but so far, the location, geometry and kinematics of the causative fault are still poorly understood. In this study we provide preliminary results of the most technologically advanced ultra-high-resolution geophysical method used to reveal the 3D faulting pattern, the late Quaternary slip rate and the earthquake potential of the marine fault system located close to the densely populated west coast of Calabria.</p>

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