scholarly journals High Resolution Attenuation Images From Active Seismic Data: The Case Study of Solfatara Volcano (Southern Italy)

2020 ◽  
Author(s):  
Guido Russo ◽  
Vincenzo Serlenga ◽  
Grazia De Landro ◽  
Ortensia Amoroso ◽  
Gaetano Festa ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Physical State ◽  
Southern Italy ◽  
Reference Model ◽  
P Wave ◽  
Small Scale ◽  
Quality Factors ◽  
Perturbative Approach ◽  
Attenuation Model

<p>The anelastic attenuation of rocks strongly depends on the contained fluid physical state and saturation. Furthermore, it is more sensitive than elastic parameters to changes in the physical state of materials. In a geologically complex  volcanic context, where fluids play a very important role, anelastic imaging of the subsoil is therefore a very powerful tool for a better understanding of its dynamics.</p><p>In this study we present a robust workflow aimed at retrieve accurate 1-D and 3-D anelastic models from the processing of active seismic data, in terms of lateral and depth variations of P-wave quality factors Q<sub>P</sub>. This methodology has been applied to data collected during a high resolution active seismic experiment in a very small-scale volcanic volume, the Solfatara crater, within Campi Flegri caldera, Southern Italy. The presented methodology is developed in three distinct steps: 1) the active seismic data have been properly processed and analyzed for measuring the t* attenuation parameter for all possible source-receivers couples. First, the source contribution has been removed by cross-correlating the recorded signal with the sweep function of the Vibroseis, which was the adopted active seismic source. Then, the spectral decay method has been applied in order to compute the t* values. 2) A reference 1-D attenuation model has been retrieved by means of a grid search procedure aiming at finding the 1-D Qp structure that minimizes the residual between the average observed t* and the theoretical t* distributions. The obtained starting reference model allowed to build a preliminary map of t* residuals through which the retrieved t* dataset has been validated. 3) The 15,296 t* measurements have been inverted by means of a linearized, perturbative approach, in a 160 x 160 x 45 m<sup>3 </sup>tomographic grid.</p><p>The retrieved 3-D attenuation model describes the first 30 m depths of Solfatara volcano as composed of very high attenuating materials, with Qp values ranging between 5 and 40. The very low Qp values, correlated with low Vp values retrieved by a previous tomographic work carried out in the area, indicate the low consolidation degree of very superficial volcanic materials of Solfatara volcano. Finally, in the NE part of the crater, lower attenuating bodies have been imaged: it is a further hint for characterizing this area of the volcano as the shallow release of the CO<sub>2 </sub>plume through the main fumaroles of the crater.</p>

Poststack velocity analysis by separation and imaging of seismic diffractions

Geophysics ◽  
2007 ◽  
Vol 72 (6) ◽  
pp. U89-U94 ◽  
Author(s):  
Sergey Fomel ◽  
Evgeny Landa ◽  
M. Turhan Taner
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Field Data ◽  
Small Scale ◽  
Velocity Analysis ◽  
High Resolution Imaging ◽  
Diffracted Waves ◽  
Resolution Imaging ◽  
Seismic Reflections ◽  
Optimal Focusing

Small geologic features manifest themselves in seismic data in the form of diffracted waves, which are fundamentally different from seismic reflections. Using two field-data examples and one synthetic example, we demonstrate the possibility of separating seismic diffractions in the data and imaging them with optimally chosen migration velocities. Our criteria for separating reflection and diffraction events are the smoothness and continuity of local event slopes that correspond to reflection events. For optimal focusing, we develop the local varimax measure. The objectives of this work are velocity analysis implemented in the poststack domain and high-resolution imaging of small-scale heterogeneities. Our examples demonstrate the effectiveness of the proposed method for high-resolution imaging of such geologic features as faults, channels, and salt boundaries.

Deep learning Q inversion from reflection seismic data with strong attenuation using an encoder-decoder convolutional neural network: an example from South China Sea

2020 ◽  
Author(s):  
Hao Zhang ◽  
Jianguang Han ◽  
Heng Zhang ◽  
Yi Zhang
Keyword(s):  
Neural Network ◽  
Deep Learning ◽  
High Resolution ◽  
Seismic Data ◽  
Semantic Segmentation ◽  
Attenuation Effect ◽  
Attenuation Model ◽  
Reflection Seismic ◽  
Q Model ◽  
Segmentation Task

<p>The seismic waves exhibit various types of attenuation while propagating through the subsurface, which is strongly related to the complexity of the earth. Anelasticity of the subsurface medium, which is quantified by the quality factor Q, causes dissipation of seismic energy. Attenuation distorts the phase of the seismic data and decays the higher frequencies in the data more than lower frequencies. Strong attenuation effect resulting from geology such as gas pocket is a notoriously challenging problem for high resolution imaging because it strongly reduces the amplitude and downgrade the imaging quality of deeper events. To compensate this attenuation effect, first we need to accurately estimate the attenuation model (Q). However, it is challenging to directly derive a laterally and vertically varying attenuation model in depth domain from the surface reflection seismic data. This research paper proposes a method to derive the anomalous Q model corresponding to strong attenuative media from marine reflection seismic data using a deep-learning approach, the convolutional neural network (CNN). We treat Q anomaly detection problem as a semantic segmentation task and train an encoder-decoder CNN (U-Net) to perform a pixel-by-pixel prediction on the seismic section to invert a pixel group belongs to different level of attenuation probability which can help to build up the attenuation model. The proposed method in this paper uses a volume of marine 3D reflection seismic data for network training and validation, which needs only a very small amount of data as the training set due to the feature of U-Net, a specific encoder-decoder CNN architecture in semantic segmentation task. Finally, in order to evaluate the attenuation model result predicted by the proposed method, we validate the predicted heterogeneous Q model using de-absorption pre-stack depth migration (Q-PSDM), a high-resolution depth imaging result with reasonable compensation is obtained.</p>

Sensitivity of reflected and transmitted seismic data

Geophysics ◽  
1993 ◽  
Vol 58 (11) ◽  
pp. 1621-1628 ◽  
Author(s):  
Rune Mittet ◽  
Tom Houlder
Keyword(s):  
Seismic Data ◽  
Large Scale ◽  
Reference Model ◽  
Small Scale ◽  
Objective Functions ◽  
Text Type ◽  
Wave Nature ◽  
Resonant Behavior ◽  
Intermediate Size ◽  
Perturbed Model

Seismic data have been reported to carry information on both small scale and large scale medium variations, but not for intermediate size objects. This is a paradox compared to many other experiments performed with probes of wave nature, where objects of size of the smallest wavelength or larger can be resolved. The sensitivity of reflected and transmitted seismic data to medium perturbations of varying sizes is investigated. The differences between data generated in a reference model and data generated in a perturbed model are measured. Both [Formula: see text] and [Formula: see text] type objective functions are used. The kernels of the objective functions consist of either stress or particle‐velocity field components. Several experimental configurations and the sensitivity to various ways of performing the medium perturbations are analyzed. For all perturbation types that change the impedances, we find a resonant behavior in the objective functions for perturbations of size of the typical wavelength of the source. For the experiments where impedances are kept fixed, we do not find this resonance, but there is a significant contribution to the objective function for all perturbation sizes larger then the shortest wavelength. That is, seismic data are sensitive to objects of size of the smallest wavelength or larger.

Seismicity of the Erguna Region (Northeastern China): Evidence for Local Stress Redistribution

2020 ◽  
Vol 110 (2) ◽  
pp. 803-815
Author(s):  
Alena I. Seredkina ◽  
Valentina I. Melnikova ◽  
Yan B. Radziminovich ◽  
Nadezhda A. Gileva
Keyword(s):  
Seismic Data ◽  
Seismic Activity ◽  
Local Stress ◽  
Point Of View ◽  
Stress Redistribution ◽  
P Wave ◽  
Small Scale ◽  
Amplitude Spectra ◽  
First Motion ◽  
Focal Parameters

ABSTRACT We consider the seismicity of the Erguna region in northeast China (48°–51° N, 117°–123° E) which is poorly studied from seismological point of view as it is characterized by a low level of seismic activity. We calculate focal parameters (focal mechanisms, scalar seismic moments, moment magnitudes, and hypocentral depths) for seven regional earthquakes with Mw 4.2–4.6 that occurred in 2000–2017 using global seismic data of Rayleigh- and Love-wave amplitude spectra and P-wave first-motion polarities recorded at regional stations. It has been shown that the study earthquakes are of small magnitudes (Mw 4.2–4.6), of various hypocentral depths (3–37 km), and are characterized by different kinematics in their sources (normal and thrust faults, strike slips). The different faulting mechanisms could reflect local stress redistribution in small-scale crustal blocks bordered by local short-length nonconnecting faults. The available geophysical and geological data evidence that the observed features of the seismic process in the Erguna region—low-seismic activity and inhomogeneity of the stress-strain field—are likely to be controlled by the structure of the crust and the upper mantle.

High‐resolution crosswell imaging of a west Texas carbonate reservoir: Part 1—Project summary and interpretation

Geophysics ◽  
1995 ◽  
Vol 60 (3) ◽  
pp. 667-681 ◽  
Author(s):  
Jerry M. Harris ◽  
Richard C. Nolen‐Hoeksema ◽  
Robert T. Langan ◽  
Mark Van Schaack ◽  
Spyros K. Lazaratos ◽  
...  
Keyword(s):  
High Resolution ◽  
High Frequency ◽  
Large Scale ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Small Scale ◽  
Observation Well ◽  
Traveltime Tomography ◽  
Seismic Profiling ◽  
West Texas

A carbon dioxide flood pilot is being conducted in a section of Chevron’s McElroy field in Crane County, west Texas. Prior to [Formula: see text] injection, two high‐frequency crosswell seismic profiles were recorded to investigate the use of seismic profiling for high‐resolution reservoir delineation and [Formula: see text] monitoring. These preinjection profiles provide the baseline for time‐lapse monitoring. Profile #1 was recorded between an injector well and an offset observation well at a nominal well‐to‐well distance of 184 ft (56 m). Profile #2 was recorded between a producing well and the observation well at a nominal distance of 600 ft (183 m). The combination of traveltime tomography and stacked CDP reflection amplitudes demonstrates how high‐frequency crosswell seismic data can be used to image both large and small scale heterogeneity between wells: Transmission traveltime tomography is used to image the large scale velocity variations; CDP reflection imaging is then used to image smaller scale impedance heterogeneities. The resolution capability of crosswell data is clearly illustrated by an image of the Grayburg‐San Andres angular unconformity, seen in both the P‐wave and S‐wave velocity tomograms and the reflection images. In addition to the imaging study, cores from an observation well were analyzed to support interpretation of the crosswell images and assess the feasibility of monitoring changes in [Formula: see text] saturation. The results of this integrated study demonstrate (1) the use of crosswell seismic profiling to produce a high‐resolution reservoir delineation and (2) the possibility for successful monitoring of [Formula: see text] in carbonate reservoirs. The crosswell data were acquired with a piezoelectric source and a multilevel hydrophone array. Both profiles, nearly 80 000 seismic traces, were recorded in approximately 80 hours using a new acquisition technique of shooting on‐the‐fly. This paper presents the overall project summary and interpretation of the results from the near‐offset profile.

Acquisition, processing and interpretation of high-resolution seismic data using a small-scale multi-channel system: an example from the Korea Strait inner shelf, south-east Korea

2016 ◽  
Vol 47 (4) ◽  
pp. 341-351 ◽  
Author(s):  
Dong-Geun Yoo ◽  
Nam-Hyung Koo ◽  
Ho-Young Lee ◽  
Byoung-Yeop Kim ◽  
Young-Jun Kim ◽  
...  
Keyword(s):  
High Resolution ◽  
Seismic Data ◽  
Small Scale ◽  
Inner Shelf ◽  
Channel System ◽  
Korea Strait

scholarly journals Estimating quality factor and mean grain size of sediments from high-resolution marine seismic data

Geophysics ◽  
2008 ◽  
Vol 73 (4) ◽  
pp. G19-G28 ◽  
Author(s):  
Luke J. W. Pinson ◽  
Timothy J. Henstock ◽  
Justin K. Dix ◽  
Jonathan M. Bull
Keyword(s):  
Grain Size ◽  
High Resolution ◽  
Quality Factor ◽  
Seismic Data ◽  
Spectral Ratio ◽  
Quality Factors ◽  
Grain Sizes ◽  
Seismic Quality Factor ◽  
Mean Grain Size ◽  
Marine Seismic

Seismic quality factor has the potential to characterize sediment properties but seldom is used by the industry for offshore site investigations because of practical difficulties with reflection seismology (e.g., restricted bandwidth) and because of uncertainties in rock-physics models. A spectral-ratio analysis of high-resolution marine seismic data can determine a quality factor to within a 95% confidence of [Formula: see text] within the uppermost [Formula: see text] of unconsolidated marine sediments. Our spectral-ratio technique does not require assumptions on how attenuation scales with frequency. Emphasis is placed on interpretation of spectral signatures before applying an iteratively reweighted robust least-squares regression to subdue the effects of noise and local heterogeneities when determining the quality factor of a sediment package. We combined data from boomer and chirp sources toexamine attenuation over four octaves of frequency [Formula: see text] and to demonstrate that expanding the frequency range improves the precision and accuracy of quality-factor fits. We obtain frequency-independent quality factors with 95% confidence intervals of 135 [Formula: see text] and 107 [Formula: see text] for silty clays with mean grain sizes of 7.7 and [Formula: see text], respectively, and 63 [Formula: see text] for a modern sand deposit with mean grain size [Formula: see text], from the Solent (U. K.). Sediments with higher quality factors require more independent observations to achieve a desirable 95% confidence. We required only 45 traces over sands and 1250 traces over the lowest attenuating silty clays. By constructing an empirical model of quality factor against mean grain size from published sediment studies, the mean grain sizes of our Solent sediments can be located, and we find that quality factor can be used to distinguish between coarse grain-dominated and clay-dominated sediments.

scholarly journals Correction of water column height variation on 2D grid high-resolution seismic data using dGPS based methodology

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Ayobami Abegunrin ◽  
Daniel A. Hepp ◽  
Tobias Mörz
Keyword(s):  
High Resolution ◽  
Water Column ◽  
Seismic Data ◽  
Column Height ◽  
Small Scale ◽  
Seismic Profiles ◽  
Shallow Marine ◽  
Sea Floor ◽  
The North ◽  
Water Column Height

Abstract Variations in the physical properties of water column usually impede exact water column height correction on high-resolution seismic data, especially when the data are collected in shallow marine environments. Changes in water column properties can be attributed to variation in tides and currents, wind-generated swells, long and short amplitude wave-fronts, or variation in salinity and water temperature. Likewise, the proper motion of the vessel complicates the determinability of the water column height. This study provides a less time-consuming and precise differential Global Positioning System based methodology that can be applied to most types of high-resolution seismic data in order to significantly improve the tracking and quality of deduced geological interpretations on smaller depth scales. The methodology was tested on geophysical profiles obtained from the German sector of the North Sea. The focus here was to identify, distinguish and classify various sub-surface sedimentary structures in a stratigraphically highly complex shallow marine environment on decimeter small-scale. After applying the correction to the profiles, the sea floor, in general, occurs 1.1 to 3.4 m (mean of 2.2 m) deeper than the uncorrected profiles and is consistent with the sea floor from published tide corrected bathymetry data. The corrected seismic profiles were used in plotting the depth of the base of Holocene channel structures and to define their gradients. The applied correction methodology was also crucial in glacial and post-glacial valley features distinction, across profile correlation and establishing structural and stratigraphic framework of the study area.

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