Seismic Property Research Articles

Condition Assessment of August A. Busch Bridge Deck Using Portable Seismic Property Analyzer and Ground Penetrating Radar

Ground penetrating radar (GPR) and the portable seismic property analyzer (PSPA) have been extensively used in the past two decades for monitoring, quantifying, and mapping the deterioration of bridge decks. Using PSPA and GPR ensures regular monitoring of bridge conditions, leads to the early detection of deterioration. This research is to address the condition of August A. Busch bridge deck owned by the Missouri Department of Conservation. Visual inspection, GPR, and PSPA data were acquired on the bridge deck. Over 90% of the bridge deck was in fair to good condition with an average compressive strength of over 2500 psi. GPR data showed no indication of significant deterioration. The overall bridge deck was determined to be in fair to good condition.

Condition Assessment Using None Destructive Tests at Montauk Bridge Deck

Abstract: Ground penetrating radar (GPR) and portable seismic property analyzer (PSPA), was used in concrete structures for monitoring, quantifying, and mapping the deterioration of bridge decks. The Montauk Bridge deck was assessed based on PSPA and GPR data. Based on the analysis of the PSPA data, it was determined that over 65% of bridge conditions were rated serious to poor condition with an average compressive strength of less than 2500 psi; less than 35% of bridge deck conditions were rated fair to good with an average compressive strength over 2500 psi. Based on GPR data, it was determined that 72% of the bridge deck was in serious to poor condition, and only 28% of the bridge deck was in fair to good condition. Additionally, the analyses of the ground penetrating radar data indicated possible rebar corrosion in places. For these reasons, it is recommended that the Montauk bridge’s deck be completely replaced. Keywords: Condition assessment, NDT, GPR, PSPA, bridge deck

Using relative geologic time to constrain convolutional neural network-based seismic interpretation and property estimation

Three-dimensional seismic interpretation and property estimation is essential for subsurface mapping and characterization, in which machine learning, particularly supervised convolutional neural network (CNN), has been extensively implemented for improved efficiency and accuracy in the past few years. However, in most seismic applications, the amount of available expert annotations often is limited, which raises the risk of overfitting a CNN, particularly when only seismic amplitudes are used for learning. In such a case, the trained CNN would have poor generalization capability, causing the interpretation and property results of obvious artifacts, limited lateral consistency, and thus restricted application to following interpretation/modeling procedures. Our study proposes addressing such an issue by using relative geologic time (RGT), which explicitly preserves the large-scale continuity of seismic patterns, to constrain a seismic interpretation and/or property estimation CNN. Such constrained learning is enforced twofold: (1) from the perspective of input, the RGT is used as an additional feature channel besides seismic amplitude, and more innovatively (2) the CNN has two output branches, with one for matching the target interpretation or properties and the other for reconstructing the RGT. In addition, multiplicative regularization is used to facilitate the simultaneous minimization of the target-matching loss and the RGT-reconstruction loss. The performance of such an RGT-constrained CNN is validated by two examples, facies identification in the Parihaka data set and property estimation in the F3 Netherlands data set. Compared with those purely from seismic amplitudes, the facies and property predictions using the proposed RGT constraint demonstrate significantly reduced artifacts and improved lateral consistency throughout a seismic survey.

Transverse seismic vulnerability analysis of tunnels based on modified IDA method

Vulnerability analysis is a crucial method to study the seismic performance of tunnels. Two benchmark cross-sections of tunnels, namely circular and rectangular cross-sections, are selected as the research object to investigate the transverse seismic property of tunnels. A finite element model is established by SAP2000 software, and the influences of various site types, depths of burial of the tunnel, and cross-section sizes on the transverse seismic capacity of a tunnel are discussed. The probabilistic seismic demand model of ground motion intensity measures and the engineering demand parameters are determined by utilizing a modified incremental dynamic analysis (IDA) method, and the reasonable ground motion intensity measures are specified by analyzing four evaluation criteria. The failure probability of the structure under each earthquake intensity and the seismic vulnerability curve of the construction are calculated to evaluate the transverse seismic performance of the tunnel by combining the probabilistic seismic demand model with the limits on the engineering demand parameters. The numerical results indicate that PGA is the ground motion intensity measure suitable for the transverse seismic performance of the tunnels. The site type has the most significant influence on the structural damage, and site type IV is the most dangerous under an earthquake. The tunnel has better seismic resistance in the elastoplastic stage, and a tunnel with a large depth of burial is more hazardous than the one with a small depth of burial. A tunnel with a large cross-section has a higher probability of damage than the one with a small cross-section.

A New Method To Estimate Resistivity Distribution Of Shaly Sand Reservoirs Using New Seismic Attributes

A subsurface resistivity model is important in hydrocarbon exploration primarily in the controlled-source electromagnetic (CSEM) method. CSEM forward modelling workflow uses resistivity model as the main input in feasibility studies and inversion process. The task of building a shaly sand resistivity model becomes more complex than clean sand due to the presence of a shale matrix. In this paper, a new approach is introduced to model a robust resistivity property of shaly sand reservoirs. A volume of seismic data and three wells located in the K-field of offshore Sarawak is provided for this study. Two new seismic attributes derived from seismic attenuation property called SQp and SQs are used as main inputs to predict the volume of shale, effective porosity, and water saturation before resistivity estimation. SQp attribute has a similar response to gamma-ray indicating the lithological variation and SQs attribute is identical to resistivity as an indicator to reservoir fluids. The petrophysical predictions are performed by solving the mathematical step-wise regression between the seismic multi-attributes and predicted petrophysical properties at the well locations. Subsequently, resistivity values are estimated using the Poupon-Leveaux (Indonesia) equation, an improvised model from Archie’s to derive the mathematical relationship of shaly sand’s resistivity to the volume and resistivity of clay matrix in shaly sand reservoirs. The resistivity modeled from the predicted petrophysical properties distributed consistently with sand distribution delineated from SQp attribute mainly in southeast, northeast, and west regions. The gas distribution of the net sand modeled by 5% and 90% of gas saturation scenarios also changed correspondingly to SQs attribute anomaly indicating the consistent fluid distribution between the modeled resistivity and SQs attribute.

Seismic performance evaluation of steel building frames with modified dual-pipe damper

Building performance against resistance to earthquake depends on selection of right building material with right properties. Steel frame structures are widely accepted due to its flexibility and seismic resistance property. However the practice of seismic retrofitting techniques in steel structures helps in the betterment of seismic performance of the building. A number of researches on simple and cost effective Metallic Yielding Device (MYD) are being conducted to evolve the best equipment. Dual-Pipe Damper (DPD) is one of the MYDs, which works on the principle of passive energy dissipation. A recent study brings the effective dimensions of pipes in DPD which can be implemented in a steel building frame conforming to IS 800:2007. This paper aims to study the effect of number of pipes in DPD by conducting parametric study using push over analysis. Three different configurations of optimized DPD installation in the multi-storey building frame are also studied. The Modal and Time-History analyses are performed on multi-storey frame with optimized DPD fixed at three configurations of steel frame conforming to IS 800:2007 to optimize the configuration.

Well-Based Quantitative Reservoir Characterization of Eocene Sokor-1 Formation, Termit Basin, Niger

The Eocene Sokor1 Formation is proven oil reservoir rocks in the Termit sub-basin. These sandstone intervals are deeply buried, highly heterogeneous in character and characterized by Low Contrast Low Resistivity (LCLR) log responses. Petrophysical and quantitative well-based rock physics interpretations were integrated for property estimations, fluid and lithology typing in reservoir characterization. Six (6) reservoir sandstone intervals were identified, delineated and correlated across five (5) wells. The estimated petrophysical properties showed that the Eocene Sokor1 sandstones have averagely good reservoir properties with sand_5 interval exhibiting exceptional reservoir properties. Vp/Vs vs. AI and μρ vs. λρ elastic cross-plots color coded with reservoir properties (Vsh and Φ), show distinct and well separated data clusters signifying hydrocarbon bearing sandstones, brine sandstones and shales/mudstones in the 3D crossplot planes with varying seismic elastic property values in each well thereby, enhancing reservoir characterization and providing information’s about the burial history, reservoir quality and property distribution in the sub-basin. The analysis suggests that, although the reservoir interval has averagely good petrophysical properties in all wells, the seismic elastic crossplots show that these properties are much better distributed in wells 2 and 3 than in wells 4, 5 and 9. Therefore, sand_5 reservoir interval in wells 2 and 3 is likely to be more hydrocarbon bearing and productive than wells 4, 5 and 9 in the sub-basin.

Pre‐Alpine Fault Fabrics in Mantle Xenoliths From East Otago, South Island, New Zealand

AbstractWe present a quantitative microstructural and seismic property analysis of harzburgitic and lherzolitic xenoliths from East Otago, New Zealand. Olivine crystallographic preferred orientations (CPOs) are dominated by orthorhombic CPOs with a tight maxima of [100] orthogonal to (010). Orthopyroxene showed the [001] axes aligned (sub)parallel to the [100] axes of olivine and the (100) plane subparallel to the (010) plane of olivine. Misorientations of olivine subgrain boundaries indicate that dislocations with [100] slip vectors are common and CPOs are interpreted as olivine [100] representing the flow direction and (010) the shear plane. Olivine grains are coarse with lobate grain boundaries, indicative of grain boundary migration at high temperatures. Olivine contains numerous subgrains whilst orthopyroxene is mostly strain‐free and it is possible that orthopyroxene crystallized from melt during deformation. Clinopyroxene lamellae in orthopyroxene, relate to decompressional cooling prior to Alpine Fault movement. Seismic properties derived from the measured CPOs, indicate P‐wave and S‐wave anisotropies at mantle conditions of 4%–10% and 3%–9%, respectively. Calculated shear wave splitting delay times of 0.1–0.9 s, for the current lithospheric mantle thickness, fit seismological observations, suggesting that the xenoliths may be representative of the lithospheric mantle that lies below East Otago today. To explain the seismic data, olivine [100] needs to be subhorizontal and parallel to NNW‐SSE fast polarization directions with [010] subhorizontal and perpendicular to these directions. This is consistent with the East Otago lithospheric mantle containing a fossil vertical shear zone with NNW‐SSE strike slip motion.

Low Cycle Fatigue Performance and Failure Analysis of Reinforcing Bar

Low cycle fatigue (LCF) behaviour and associated failure mechanisms of a thermo-mechanically treated Fe 500D steel rebar have been experimentally evaluated with a view to assess its performance under seismic condition. The total axial strain-controlled LCF tests have been performed at five different strain amplitudes (± 0.30 to ± 1.00%) at ambient temperature until failure maintaining a constant true strain rate of 1 × 10− 3 s− 1 and a fixed strain ratio of − 1. Fatigue data have been analysed following both strain–life and plastic strain energy–life relationships; while, macro as well as micro features of the failed specimens, have been critically examined. These are supplemented by microstructural characterizations in addition to tensile and hardness measurements. Significant reduction of yield strength is recorded under dynamic loading which is responsible for considerable cyclic softening of rebar till failure in all strain amplitudes indicating the deterioration of seismic resistance property. Both strain–life and plastic strain energy–life relationships are found to accurately predict the cyclic plastic behaviour of the selected rebar. A near Masing behaviour is established by three different analytical approaches. The fatigue crack is always found to initiate at the transverse rib root and primarily propagates alongside the rim region.

Mapping the 3D extent of the Stillwater Complex, Montana—Implications for potential platinum group element exploration and development

Geophysical models characterize the exposed and interpreted buried extent of the Stillwater Complex, critical for understanding the origin of the layered mafic intrusion and its associated high-grade platinum group element resources. The 3D models, constrained by gravity, magnetic, xenolith, seismic, borehole, and rock property data indicate that the likely maximum extent of the Stillwater Complex beneath Phanerozoic cover is ~10 times greater than its outcrop, ~2240 km2. The thickness values are poorly constrained but vary from ~7000 to 12,000 m, depending on crustal and mantle density variations and depths to the top of the lower crust and mantle. This thickness may include dense metasedimentary units of the basin into which the Stillwater Complex intruded. Using the modeled thickness results in a volume estimate of ~24,700 km3, albeit poorly constrained. New analyses of xenoliths from the Cretaceous Sliderock and Suzie Peak intrusions produce ages of 2706–2716 Ma, corresponding to the age of the Stillwater Complex, and 2813 Ma, corresponding to the age of Archean gneissic basement. Seismic reflectors in inferred Archean crystalline basement, possibly including the Stillwater Complex, dip ~25–30° north, with segments dipping as much as 70° north. Layered reflectors beneath the Phanerozoic sedimentary section and above the inferred Archean crystalline basement may represent metasedimentary units, perhaps a southern extension of the Mesoproterozoic Belt Basin. The potential field models and the seismic reflection data suggest that the Stillwater Complex was dipping northward prior to deposition of Cambrian strata, perhaps uplifted in the late Archean or Proterozoic as previously proposed, and that during Laramide times, faulting and intrusions highly disrupted the complex. Temperature measurements from boreholes help constrain the depths of feasible mining of the complex.

Locating Spatial Changes of Seismic Scattering Property by Sparse Modeling of Seismic Ambient Noise Cross‐Correlation Functions: Application to the 2008 Iwate‐Miyagi Nairiku (Mw6.9), Japan, Earthquake

AbstractLocating change regions of seismic velocities and seismic scattering properties associated with volcanic activities and earthquakes is important for structural monitoring. To increase such applications, we propose to use sparse modeling to estimate spatial distributions of seismic scattering property changes. The sparse modeling is an inversion technique that enables us to estimate model parameters from a small data set with sparsity condition such asℓ1norm regularization. We apply this technique to seismic ambient noise cross‐correlation functions from 17 Hi‐net stations around the epicenter of the 2008 Iwate‐Miyagi Nairiku, Japan, earthquake (Mw=6.9). We compute waveform decoherences at the 0.5–1 Hz band and invert the waveform decoherences for the spatial distributions of seismic scattering property changes. Just after the main shock, the largest change occurred at the south of the epicenter, and the maximum change of the scattering coefficient in this region is estimated to be 0.032 km−1. The result from an ordinary linear least squares inversion with theℓ2norm regularization is almost consistent with that from the sparse modeling. Moreover, we confirm the superiority of sparse modeling in imaging with smaller data sets. Only five seismic stations that are deployed near the epicenter so as to surround the change regions are necessary to retrieve the result from 17 stations. On the other hand, in the case of theℓ2norm regularization, we need at least 15 stations. The sparse modeling will be helpful to estimate the spatial distribution of seismic scattering property changes from a small data set.

Compaction, rock physics and rock properties of sandstones of the Stø Formation: Case study of five wells from the south-western Barents Sea, Norway

Five wells containing Lower-Middle Jurassic sandstones of Stø Formation from the Hammerfest Basin (7120/9–1, 7121/7–1), the Ringvassøy-Loppa Fault Complex (7119/12–1, 7119/12–4) and the Troms-Finnmark Fault Complex (7019/1-1) in the Barents Sea area are considered in this study. The Stø Formation sandstones contain dominantly very fine-to medium-grained quartz arenites with occasional coarse-grained sandstone layers. Feldspathic and quartz wackes are also present. The effect of compaction and exhumation on reservoir properties (porosity and permeability) and seismic property (P-wave velocity) of these sandstones have been investigated. Source of quartz cement has also been investigated. Forty polished thin sections embedded in blue epoxy were studied using optical microscopy, scanning electron microscopy and cathodoluminiscence. Bulk mineralogy was also analysed using X-ray diffraction.The studied sandstones have experienced Cenozoic exhumation ranging between 820 and 1050 m. P-wave velocity is higher; porosities and permeabilities are lower in the western wells (7019/1-1, 7119/12–1 and 7119/12–4) compared to the eastern wells (7120/9–1 and 7121/7–1). Rock physics models and diagnostics show that the western wells are diagenetically more mature, stiffer, more compacted and more cemented than the eastern wells. These trends are attributed largely to difference in burial history from the east to the west and less to textural variations. Quartz cement is the most important authigenic mineral in these sandstones. Quartz cement in the western well (7119/12–1) is predominantly derived from clay-induced dissolution at macrostylolites whereas the eastern wells (7120/9–1 and 7121/7–1) are mostly sourced from clay-induced dissolution at grain contacts or microstylolites. While cementational porosity loss dominates in the western wells, compactional porosity loss dominates in the eastern wells. Compaction can reduce porosities down to 26% and this might be the reason for better porosity preservation and reservoir quality in the eastern wells than in the western wells.

Seismic multiattribute for predicting reservoir properties: Case study of globigerina limestone reservoir, Madura Strait

Hydrocarbon exploration requires comprehensive understanding of geological and geophysical properties of subsurface reservoir. Therefore, subsurface rock properties determination, which include total and effective porosity, clay content, and water saturation, is a very important, particularly for reservoir target. In term of spatial coverage, subsurface rock properties are then distributed by using seismic multiattribute, which is performed in two approaches – linear multivariate regression and probabilistic neural network (PNN). Linear multivariate regression seismic multiattribute assumes that the relation of seismic attributes and reservoir property is linear, while probabilistic neural network, seismic multiattribute assumes non-linear relationship. This research employed linear multivariate regression using internal attribute of seismic data to predict several rock properties. Transformation of seismic internal attribute to rock properties was attained by a series of weights derived by least-squares minimization. To estimate the reliability of the derived multiattribute transform, cross validation is used where each well is systematically removed from the training set, and the transform is rederived from the remaining wells. The prediction error for the hidden well is then calculated. The validation error, which is the average error for all hidden wells, is used as a measure of the likely prediction error when the transform is applied to the seismic volume. This method was applied to Globigerina Limestone reservoir in Madura Strait that resulted in good prediction of reservoir properties. Result of this research is used for quantification of remaining lead and prospect in the field area. Furthermore, the predicted subsurface rock properties are used as input to optimize in developing well in the proven fields.

Study on seismic behavior reduction of typical joints for monolithic precast concrete frame structures with ages

PurposeMonolithic precast concrete frame structures have been promoted and developed in recent years. Owing to material deterioration and a weaker structural integrity, monolithic precast concrete frame structures may suffer from insufficient seismic capacity as service time increases. A typical joint of monolithic precast concrete frame structure is studied in this paper. The purpose of this paper is to perform numerical modeling of the typical joint subjected to low cyclic load at different ages and analyze the hysteretic behavior reduction with ages under common atmosphere environment.Design/methodology/approachExisting un-carbonated concrete, carbonated concrete and corroded rebar are all considered as deterioration factors for the typical joint, whose constitutive models are introduced into the finite element model to study. Moreover, time-dependent constitutive model of existing un-carbonated concrete and mechanical model of bond between precast and cast-in-place concrete are established on the basis of existing experimental data. Then, finite element method is used to investigate the seismic property reduction of the typical joint, where nonlinear springs are set to simulate bonding between precast and cast-in-place concrete.FindingsAnalyzing the results, the reduction of reaction force from skeleton curves of the joint is significant in the first 30 years of service time, and slows down after 30 years. Besides, the ductility, secant stiffness and equivalent viscous damping coefficient of the typical joint remain almost unchanged in the first decade, but decrease obviously after 10 years.Originality/valueThe originality of the paper consists in the following. The time-dependent constitutive model of existing un-carbonated concrete is established and used in finite element method. Besides, bonding between precast and cast-in-place concrete is considered using nonlinear springs. There is a reference value for the seismic performance assessment of existing monolithic precast concrete frame structures.

Seismic Property and Its Effect on Abrasion in the West Leihitu Coastal region, Ambon Island

This research was carried out in the West Leihitu coastal region, Ambon Island. The purpose of this study is to study seismic properties and their effects on coastal abrasion based on seismic geological conditions as an indicator of abrasion rate. Peak Ground Acceleration (PGA) values of each coastal area have a range (19,722-41,130) gal, with the highest value in the Negeri Liliboi at 41,130 gal. PGA values do not represent Ground Shear Strain (GGS) levels or have an impact on rock deformation in coastal areas. This can be seen from the GGS of the Negeri Liliboi coastal area which is higher (γ = 1.459 × 10-5) when compared to Negeri Alang coastal area (γ = 2,561 × 10-5) although the Peak Land Acceleration (PGA) value is large. Based on these results, Negeri Alang and Negeri Liliboy have high soil susceptibility resulting in soil structure cracking and soil degradation. This is the potential for abrasion in coastal areas. Geological conditions on the West Leihitu coastal region consist of land classification types II, III and IV namely gravel sand, alluvial rocks, and buff formations and alluvial rocks formed from sedimentation with a very thick layer thickness in general.

Dynamic response analysis of machine bridge of spillway gate

Under the action of earthquake, the seismic property of the machine bridge directly affects the normal use of spillway gate. At the same time, the type of infilled wall affects the seismic capacity of the machine bridge. To decrease the damage possibility of the machine bridge under earthquake, three finite element models are established by finite element software, and the dynamic time history analysis of the machine bridge is carried out. The stress and displacement of different models are obtained through the dynamic time history analysis. The best type of infilled wall is judged by comparing the seismic responses of three models. Based on the analysis results, the mechanical characteristics of the machine bridge under earthquake action are analyzed and the weak position of the structure is found. Therefore, some measures can be taken to further improve the seismic performance of the machine bridge. The calculation results have important significance for practical engineering.

Dynamic characteristic analysis of double-column machine bridge of spillway gate

The machine bridge has problems in many earthquake cases, such as cracking at the end of the column, excessive local displacement, and even severe damage. To improve the seismic property of the machine bridge, a new design method is proposed, namely the double-column machine bridge. The finite element analysis is used to analyze the dynamic time history of the structure, and the stress and displacement of the structure during the earthquake action are studied. In addition, the collision analysis between the machine bridges is carried out, which is based on the results of the three-dimensional finite element calculation. The results show that the double-column machine bridge has better seismic performance. Compared with the ordinary machine bridge, the displacement and stress of the new structure under the large earthquake are obviously reduced. By optimizing the structure, the collision between structures can be effectively avoided.

Shaking table test study on the functionality of rubber isolation bearing used in underground structure subjected to earthquakes

Steel-reinforced rubber isolation bearing has been widely adopted in ground structures to improve structural seismic resistance property. However its use in underground structures is not elaborately examined. Through a series of shaking table tests, the functionality of isolation bearings connected to structural intermediate columns' feet in underground structure during seismic actions is investigated, compared with the dynamic response characteristics of model structure with general reinforced concrete columns. Result analysis shows that dynamic reaction of underground structure is fundamentally determined by soil motions, the isolation bearing can not shift structural fundamental period away from the prominent frequency of seismic waves to enhance structural seismic resistance capacity like the way in the case of ground structures. However, as the soil-structure interaction changes a lot along structure height, isolation bearings can effectively obstruct lateral shear forces developed in top structural part from transferring into down structural part, which will avoid force concentration in low structural part, making structural deformation distributed uniformly along structure height in comparison with the deformation in structure without isolation device. Other changes of underground structural dynamic reactions to earthquakes brought out by isolation device will be also detailed.

The Alba Field, Block 16/26a, UK North Sea

Abstract The Alba Field is a relatively heavy oil accumulation lying in an Eocene deep-water channel complex in Block 16/26a of the Central North Sea. With an estimated 880 MMbbl in place, the reservoir is characterized by thick, high net/gross sands with excellent reservoir properties and rock physics favourable for seismic property detection. The field has been developed by horizontal production wells, with pressure support provided by seawater injectors. After 24 years of production, more than 427 MMbbl have been recovered. Over the course of the development, the results of development drilling and improved reservoir imaging from seismic have revealed greater reservoir complexity than anticipated at sanction. The highly irregular reservoir geometry is likely to reflect the internal stacking patterns of channel elements within the channel complex that are locally overprinted by post-depositional remobilization. This increased reservoir complexity has required more wells to effectively drain the expected volumes. Despite this, recovery has exceeded estimates from the initial field development plan, reflecting an extremely efficient waterflood. 4D seismic spectacularly images extensive sweep away from injectors and excellent reservoir connectivity. Throughout the development, the application of seismic technologies has been a key enabler for effective reservoir management and, looking forward, maximizing value.

Estimation of total fatigue life for in-service asphalt mixture based on accelerated pavement testing and four-point bending beam fatigue tests

The purpose of this study was to estimate the total fatigue life for in-service asphalt mixture fatigue with in situ accelerated pavement testing (APT) and laboratory four-point bending beam tests. On a selected expressway in Shanghai, China, a series of full-scale APT tests were conducted. During the APT tests, a portable seismic property analyzer was used to monitor the pavement deterioration through modulus reduction. An equivalent factor between the APT loading and equivalent single axle loads (ESALs) was estimated. Additionally, asphalt concrete slabs were cut from the APT test sections and then transferred to the laboratory for four-point bending beam fatigue tests. A new fatigue equation was proposed for the in-service asphalt mixtures. Furthermore, a shift factor between the laboratory fatigue life and field ESAL was recommended. Finally, the field total fatigue life of the in-service asphalt mixture was estimated based on all the work in this study.