scholarly journals Characterization of a complex near-surface structure using well logging and passive seismic measurements

Solid Earth ◽  
2016 ◽  
Vol 7 (2) ◽  
pp. 685-701 ◽  
Author(s):  
Beatriz Benjumea ◽  
Albert Macau ◽  
Anna Gabàs ◽  
Sara Figueras
Keyword(s):  
Wave Velocity ◽  
Upper Cretaceous ◽  
Well Logging ◽  
P Wave ◽  
Ratio Method ◽  
Geophysical Field ◽  
Near Surface ◽  
Passive Seismic ◽  
Surface Geology ◽  
Seismic Measurements

Abstract. We combine geophysical well logging and passive seismic measurements to characterize the near-surface geology of an area located in Hontomin, Burgos (Spain). This area has some near-surface challenges for a geophysical study. The irregular topography is characterized by limestone outcrops and unconsolidated sediments areas. Additionally, the near-surface geology includes an upper layer of pure limestones overlying marly limestones and marls (Upper Cretaceous). These materials lie on top of Low Cretaceous siliciclastic sediments (sandstones, clays, gravels). In any case, a layer with reduced velocity is expected. The geophysical data sets used in this study include sonic and gamma-ray logs at two boreholes and passive seismic measurements: three arrays and 224 seismic stations for applying the horizontal-to-vertical amplitude spectra ratio method (H/V). Well-logging data define two significant changes in the P-wave-velocity log within the Upper Cretaceous layer and one more at the Upper to Lower Cretaceous contact. This technique has also been used for refining the geological interpretation. The passive seismic measurements provide a map of sediment thickness with a maximum of around 40 m and shear-wave velocity profiles from the array technique. A comparison between seismic velocity coming from well logging and array measurements defines the resolution limits of the passive seismic techniques and helps it to be interpreted. This study shows how these low-cost techniques can provide useful information about near-surface complexity that could be used for designing a geophysical field survey or for seismic processing steps such as statics or imaging.

scholarly journals Characterization of a complex near-surface structure using well logging and passive seismic measurements

2016 ◽  
Author(s):  
Beatriz Benjumea ◽  
Albert Macau ◽  
Anna Gabàs ◽  
Sara Figueras
Keyword(s):  
Wave Velocity ◽  
Upper Cretaceous ◽  
Seismic Velocity ◽  
Well Logging ◽  
P Wave ◽  
Geophysical Field ◽  
Near Surface ◽  
Passive Seismic ◽  
Surface Geology ◽  
Seismic Measurements

Abstract. We combine geophysical well logging and passive seismic measurements to characterize the near surface geology of an area located in Hontomin, Burgos (Spain). This area has some near-surface challenges for a geophysical study. The irregular topography is characterized by limestone outcrops and unconsolidated sediments areas. Additionally, the near surface geology includes an upper layer of pure limestones overlying marly limestones and marls (Upper Cretaceous). These materials lie on top of Low Cretaceous siliciclastic sediments (sandstones, clays, gravels). In any case, decreasing seismic velocity with depth is expected. The geophysical datasets used in this study include sonic and gamma ray logs at two boreholes and passive seismic measurements: 224 H/V stations and 3 arrays. Well logging data defines two significant changes in the P-wave velocity log within the Upper Cretaceous layer and one more at the Upper to Lower Cretaceous contact. This technique has also used for refining the geological interpretation. The passive seismic measurements provide a map of sediment thickness with maximum of around 40 m and shear-wave velocity profiles from the array technique. A comparison between seismic velocity coming from well logging and array measurements defines the resolution limits of the passive seismic techniques and helps for its interpretation. This study shows how these low-cost techniques can provide useful information about near-surface complexity that could be used for designing a geophysical field survey or for seismic processing steps such as statics or imaging.

Passive seismic imaging using microearthquakes

Geophysics ◽  
1995 ◽  
Vol 60 (4) ◽  
pp. 1178-1186 ◽  
Author(s):  
M. Reza Daneshvar ◽  
Clarence S. Clay ◽  
Martha K. Savage
Keyword(s):  
Wave Velocity ◽  
Signal To Noise Ratio ◽  
Velocity Model ◽  
P Wave ◽  
Seismic Signals ◽  
Subsurface Structure ◽  
Near Surface ◽  
P Wave Velocity ◽  
Recording Station ◽  
Passive Seismic

We have developed a method of processing seismic signals generated by microearthquakes to image local subsurface structure beneath a recording station. This technique uses the autocorrelation of the vertically traveling earthquake signals to generate pseudoreflection seismograms that can be interpreted for subsurface structure. Processed pseudoreflection data, from microearthquakes recorded in the island of Hawaii, show consistent reflectivity patterns that are interpreted as near‐surface horizontal features. Forward modeling of the pseudoreflection data results in a P‐wave velocity model that shows reasonable agreement with the velocity model derived from a refraction study in the region. Usable signal‐to‐noise ratio is obtained down to 2 s. A shear‐wave velocity model was also generated by applying this technique to horizontal component data.

Characterization of elastic properties of near-surface and subsurface deepwater hydrate-bearing sediments

Geophysics ◽  
2013 ◽  
Vol 78 (3) ◽  
pp. D169-D179 ◽  
Author(s):  
Zijian Zhang ◽  
De-hua Han ◽  
Daniel R. McConnell
Keyword(s):  
Wave Velocity ◽  
Elastic Constants ◽  
Gas Hydrate ◽  
Effective Medium Theory ◽  
Pore Space ◽  
Seismic Interpretation ◽  
P Wave ◽  
Near Surface ◽  
Free Gas ◽  
Hydrate Bearing Sediments

Hydrate-bearing sands and shallow nodular hydrate are potential energy resources and geohazards, and they both need to be better understood and identified. Therefore, it is useful to develop methodologies for modeling and simulating elastic constants of these hydrate-bearing sediments. A gas-hydrate rock-physics model based on the effective medium theory was successfully applied to dry rock, water-saturated rock, and hydrate-bearing rock. The model was used to investigate the seismic interpretation capability of hydrate-bearing sediments in the Gulf of Mexico by computing elastic constants, also known as seismic attributes, in terms of seismic interpretation, including the normal incident reflectivity (NI), Poisson’s ratio (PR), P-wave velocity ([Formula: see text]), S-wave velocity ([Formula: see text]), and density. The study of the model was concerned with the formation of gas hydrate, and, therefore, hydrate-bearing sediments were divided into hydrate-bearing sands, hydrate-bearing sands with free gas in the pore space, and shallow nodular hydrate. Although relations of hydrate saturation versus [Formula: see text] and [Formula: see text] are different between structures I and II gas hydrates, highly concentrated hydrate-bearing sands may be interpreted on poststack seismic amplitude sections because of the high NI present. The computations of elastic constant implied that hydrate-bearing sands with free gas could be detected with the crossplot of NI and PR from prestack amplitude analysis, and density may be a good hydrate indicator for shallow nodular hydrate, if it can be accurately estimated by seismic methods.

A reality check on full-wave inversion applied to land seismic data for near-surface modeling

2022 ◽  
Vol 41 (1) ◽  
pp. 40-46
Author(s):  
Öz Yilmaz ◽  
Kai Gao ◽  
Milos Delic ◽  
Jianghai Xia ◽  
Lianjie Huang ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Seismic Data ◽  
Surface Modeling ◽  
P Wave ◽  
Borehole Data ◽  
Near Surface ◽  
Traveltime Tomography ◽  
Wave Inversion ◽  
Full Wave ◽  
Elastic Inversion

We evaluate the performance of traveltime tomography and full-wave inversion (FWI) for near-surface modeling using the data from a shallow seismic field experiment. Eight boreholes up to 20-m depth have been drilled along the seismic line traverse to verify the accuracy of the P-wave velocity-depth model estimated by seismic inversion. The velocity-depth model of the soil column estimated by traveltime tomography is in good agreement with the borehole data. We used the traveltime tomography model as an initial model and performed FWI. Full-wave acoustic and elastic inversions, however, have failed to converge to a velocity-depth model that desirably should be a high-resolution version of the model estimated by traveltime tomography. Moreover, there are significant discrepancies between the estimated models and the borehole data. It is understandable why full-wave acoustic inversion would fail — land seismic data inherently are elastic wavefields. The question is: Why does full-wave elastic inversion also fail? The strategy to prevent full-wave elastic inversion of vertical-component geophone data trapped in a local minimum that results in a physically implausible near-surface model may be cascaded inversion. Specifically, we perform traveltime tomography to estimate a P-wave velocity-depth model for the near-surface and Rayleigh-wave inversion to estimate an S-wave velocity-depth model for the near-surface, then use the resulting pairs of models as the initial models for the subsequent full-wave elastic inversion. Nonetheless, as demonstrated by the field data example here, the elastic-wave inversion yields a near-surface solution that still is not in agreement with the borehole data. Here, we investigate the limitations of FWI applied to land seismic data for near-surface modeling.

scholarly journals Noise-based ballistic wave passive seismic monitoring. Part 1: body waves

2020 ◽  
Vol 221 (1) ◽  
pp. 683-691 ◽  
Author(s):  
F Brenguier ◽  
R Courbis ◽  
A Mordret ◽  
X Campman ◽  
P Boué ◽  
...  
Keyword(s):  
Seismic Velocity ◽  
Noise Source ◽  
Seismic Monitoring ◽  
Body Waves ◽  
P Wave ◽  
New Technique ◽  
Apparent Velocity ◽  
Near Surface ◽  
Velocity Increase ◽  
Passive Seismic

SUMMARY Unveiling the mechanisms of earthquake and volcanic eruption preparation requires improving our ability to monitor the rock mass response to transient stress perturbations at depth. The standard passive monitoring seismic interferometry technique based on coda waves is robust but recovering accurate and properly localized P- and S-wave velocity temporal anomalies at depth is intrinsically limited by the complexity of scattered, diffracted waves. In order to mitigate this limitation, we propose a complementary, novel, passive seismic monitoring approach based on detecting weak temporal changes of velocities of ballistic waves recovered from seismic noise correlations. This new technique requires dense arrays of seismic sensors in order to circumvent the bias linked to the intrinsic high sensitivity of ballistic waves recovered from noise correlations to changes in the noise source properties. In this work we use a dense network of 417 seismometers in the Groningen area of the Netherlands, one of Europe's largest gas fields. Over the course of 1 month our results show a 1.5 per cent apparent velocity increase of the P wave refracted at the basement of the 700-m-thick sedimentary cover. We interpret this unexpected high value of velocity increase for the refracted wave as being induced by a loading effect associated with rainfall activity and possibly canal drainage at surface. We also observe a 0.25 per cent velocity decrease for the direct P-wave travelling in the near-surface sediments and conclude that it might be partially biased by changes in time in the noise source properties even though it appears to be consistent with complementary results based on ballistic surface waves presented in a companion paper and interpreted as a pore pressure diffusion effect following a strong rainfall episode. The perspective of applying this new technique to detect continuous localized variations of seismic velocity perturbations at a few kilometres depth paves the way for improved in situ earthquake, volcano and producing reservoir monitoring.

scholarly journals Finite-difference modelling to evaluate seismic P-wave and shear-wave field data

Solid Earth ◽  
2015 ◽  
Vol 6 (1) ◽  
pp. 33-47 ◽  
Author(s):  
T. Burschil ◽  
T. Beilecke ◽  
C. M. Krawczyk
Keyword(s):  
Wave Field ◽  
Shear Wave ◽  
Field Data ◽  
P Wave ◽  
Sh Wave ◽  
Surface Shear ◽  
Near Surface ◽  
Reflection Seismic ◽  
Surface Shear Wave ◽  
Seismic Measurements

Abstract. High-resolution reflection seismic methods are an established non-destructive tool for engineering tasks. In the near surface, shear-wave reflection seismic measurements usually offer a higher spatial resolution in the same effective signal frequency spectrum than P-wave data, but data quality varies more strongly. To discuss the causes of these differences, we investigated a P-wave and a SH-wave seismic reflection profile measured at the same location on the island of Föhr, Germany and applied seismic reflection processing to the field data as well as finite-difference modelling of the seismic wave field. The simulations calculated were adapted to the acquisition field geometry, comprising 2 m receiver distance (1 m for SH wave) and 4 m shot distance along the 1.5 km long P-wave and 800 m long SH-wave profiles. A Ricker wavelet and the use of absorbing frames were first-order model parameters. The petrophysical parameters to populate the structural models down to 400 m depth were taken from borehole data, VSP (vertical seismic profile) measurements and cross-plot relations. The simulation of the P-wave wave-field was based on interpretation of the P-wave depth section that included a priori information from boreholes and airborne electromagnetics. Velocities for 14 layers in the model were derived from the analysis of five nearby VSPs (vP =1600–2300 m s-1). Synthetic shot data were compared with the field data and seismic sections were created. Major features like direct wave and reflections are imaged. We reproduce the mayor reflectors in the depth section of the field data, e.g. a prominent till layer and several deep reflectors. The SH-wave model was adapted accordingly but only led to minor correlation with the field data and produced a higher signal-to-noise ratio. Therefore, we suggest to consider for future simulations additional features like intrinsic damping, thin layering, or a near-surface weathering layer. These may lead to a better understanding of key parameters determining the data quality of near-surface shear-wave seismic measurements.

scholarly journals The potential of seismic cross-hole tomography for geotechnical site investigation

2019 ◽  
Vol 92 ◽  
pp. 18006
Author(s):  
Yannick Choy Hing Ng ◽  
William Danovan ◽  
Taeseo Ku
Keyword(s):  
Wave Velocity ◽  
Site Investigation ◽  
Velocity Model ◽  
P Wave ◽  
Reconstruction Technique ◽  
Sufficient Information ◽  
Eastern Region ◽  
S Wave ◽  
Near Surface ◽  
Soil Layers

Seismic cross-hole tomography has been commonly used in oil and gas exploration and the mining industry for the detection of precious resources. For near-surface geotechnical site investigation, this geophysical method is relatively new and can be used to supplement traditional methods such as the standard penetration test, coring and sampling, thus improving the effectiveness of site characterization. This paper presents a case study which was carried out on a reclaimed land in the Eastern region of Singapore. A seismic cross-hole test was performed by generating both compressional waves and shear waves into the ground. The signals were interpreted by using first-arrival travel time wave tomography and the arrival times were subsequently inverted using Simultaneous Iterative Reconstruction Technique (SIRT). A comparison with the borehole logging data indicated that P-wave velocity model cannot provide sufficient information about the soil layers, especially when the ground water table is near the surface. The S-wave velocity model seemed to agree quite well with the variation in the SPT-N value and could identify to a certain extent the interface between the different soil layers. Finally, P-wave and S-wave velocities are used to compute the Poisson's ratio distribution which gave a good indication of the degree of saturation of the soil.

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