Seismic Block Research Articles

Self-supervised learning for efficient seismic facies classification

Seismic facies classification is an important task in seismic interpretation that allows the identification of rock bodies with similar physical characteristics. Manual labeling of seismic data is immensely time consuming, given the recent surge in data volumes. Self-supervised learning (SSL) enables models to learn powerful representations from unlabeled data, thereby improving performance in downstream tasks using limited labeled data. We investigate the effectiveness of SSL for efficient facies classification by evaluating various convolutional and vision transformer-based models. We pretrain the models on image reconstruction and fine-tune them on facies segmentation. Results on the southern North Sea F3 seismic block in the Netherlands and the Penobscot seismic volume in the Sable Subbasin, offshore Nova Scotia, Canada, show that SSL has comparable performance to supervised learning using only 5%–10% labeled data. Further, SSL exhibits stable domain adaptation on the Penobscot data set even with 5% labeled data, indicating an improved generalization compared with the supervised learning setup. The findings demonstrate that SSL significantly enhances model accuracy and data efficiency for seismic facies classification.

Platform-to-Basin Evolution of a Tectonically Indistinct Part of a Multiple Foreland—Analysis of a 3D Seismic Block in the Northern Adriatic Sea (Croatian Offshore)

The Aiza research area covers over 650 km2 of the northern Adriatic offshore, a common Adriatic foreland of the older Dinarides on the NE, and the younger Apennines on the SW. High-quality 3D reflection seismic data were used to investigate the area’s Mesozoic to Cenozoic tectono-stratigraphic evolution. Four main seismo-stratigraphical horizons were recognized: Base of Carbonate Platform (BCP), Top of Carbonate Platform (TCP), Messinian Erosional Surface (MES), and a Plio-Quaternary horizon (PlQh), as well as the dominant faults. The results depict the geological setting and tectonic evolution of the area. A long-lasting (Jurassic to Cretaceous) stable NW-SE striking platform margin evolved probably along the inherited Triassic normal fault. The marginal belt of the platform was affected during the Late Cretaceous to Palaeogene by extension and opening of the intra-platform basin, probably on the southern limb of the then developing Dinaric forebulge. The transverse fault system (Kvarner fault) was probably reactivated as a strike-slip zone during the late Miocene tectonic reorganization. The area was tilted to the SW during the Pliocene, in the distal foreland of the progressively northward propagating Northern Apennines. Sub-horizontal late Quaternary cover of Dinaric and Apenninic structures could imply active subsidence of the foreland in between nowadays sub-vertically exhuming neighboring orogenic belts.

Reservoir characterization analysis in glacial reservoirs

This research aims to characterize reservoir properties by applying rock physics and AVO analysis followed by pre-stack inversion. Two approaches are investigated: One approach addresses the case in which there are wells and seismic data, and the other addresses cases where only seismic data are available. The former approach is achieved by using well-log cross-plots for rock physics modeling to determine the feasibility and pay zone through gas fluid substitution followed by AVO analysis. Pre-stack inversion is then used to predict porosity and gas saturation. In the second approach, a synthetic seismogram is generated and compared to the observed seismic trace at the location of interest by forward modeling P-wave interval velocity and density. The best-matching P-wave velocity and density are subsequently used to generate synthetic well logs at the same location. Pre-stack inversion is then performed on these synthetic wells to predict porosity and gas saturation. Property prediction is performed by a feasibility study and pay zone calculation using rock physics modeling of the nearest well to the seismic block. Finally, the results of this case are validated using real wells. This new approach of reservoir characterization using synthetic wells is applied on reservoir channels and yielded a fairly good porosity prediction but a less accurate prediction of gas saturation.

Feasibility experiments of seismic concrete block walls without joint mortar

The authors developed two types of block systems consisting only of main block and key block without joint mortar in consideration of seismic performance and workability. Two types of block systems have different key block shapes: One is the peanuts shape and the other is the dumbbell shape. In this study, the proposed two types of block walls as well as a typical block wall were experimentally investigated to evaluate the seismic performance. In the tests, full-scale, single-story specimens were tested under static cyclic in-plane loading, and failure patterns and cracks were carefully observed. In this paper, the loading bearing capacity, energy dissipation capacity and reuse ratio of block walls are discussed in detail. As a result, the deformability, energy absorption capacity and reuse ratio of the proposed block systems were considerably higher than those of typical block system.

Some problems vibration and protection of buiding and structures using blocks

The basic concept of vibration and seismic insulation of buildings and structures based on the use of rubber seismic blocks (RSB) is considered. The concept of seismic isolation of structures is very relevant. In Japan, New Zealand, France, Greece, England, the United States and a number of other countries, it has been successfully used to protect such important structures as nuclear power plants, schools, bridges, museums, administrative and residential buildings from earthquakes. In Ukraine, the concept developed in two ways: the development of seismic isolation blocks for earthquake protection of residential buildings; development of vibration isolation blocks for vibration protection of heavy equipment (weight up to 300 tons, used in Russia, Ukraine) and residential buildings. For the practical application of building seismic isolation systems by the N. S. Geotechnical Mechanics Institute. Experimental studies were carried out to substantiate the RSB parameters, their designs were patented, design documentation was developed and experimental samples of three types of rubber-metal seismic protection blocks with a diameter of 400 mm and 500 mm and a total height of the rubber layer: 2 120 120 mm, 2х70 mm and 2х50 mm were made. The results of the calculation of a rubber-metal seismic support used as an element of vibration-seismic protection of multi-storey residential buildings are presented. The calculation results obtained by approximate analytical methods are compared with experimental data for samples of seismic supports. The design of a pile with vibration-insulating rubber supports is considered. The developed and tested RSB structures were used for vibration protection against metro trains and vehicles of residential buildings in Kiev: a 10-section 10-storey residential building on Kikvidze Street, three 27-storey buildings on Obolonsky Avenue and a residential complex of three houses in Lviv. Vibration and seismic isolation with the help of RSB provides the natural vibration frequency of the building in the horizontal plane of less than 1 Hz, which meets the requirements of the DBN and Eurocode 8 for the design of the building seismic isolation systems.

Characterizing flow in the first hundred-meter depth of a fractured aquifer using hybrid seismic methods, acoustic logging, and flow-log measurements

Understanding subsurface flow, especially in fractured rocks only housing water through a few preferential pathways, is still challenging. The point is mainly associated with the poor accessibility of the subsurface and the lack of accurate representations for both heterogeneity and spatial distribution of water bearing bodies. This notwithstanding, highly-resolved geophysical investigations bring new images of the subsurface. This is exemplified over a fractured limestone aquifer at the site scale (for example, that of the radius of influence of an extraction well). On an experimental site, situated in the Cher region (France), two boreholes have been drilled for field experiments. Full Waveform Acoustic Logging (FWAL) and seismic experiments were conducted. Hybrid seismic imaging, which consists in combining refraction and reflection seismic results, has been carried out. Based on a four-step procedure, the processing of refracted and reflected waves provided two sections. After assemblage, these sections produced in a first step an extended time reflectivity section starting from the surface and, in a second step, a section over depth after calibration with Vertical Seismic Profile (VSP) and acoustic data. However, even the Very High Resolution (VHR) seismic methods do not have a sufficient vertical resolution to describe accurately the geological formation. The acoustic sections were processed to separate the different wave fields, to extract the criss-cross events and to build a criss-cross index log. A log of fracturation index, based on both criss-cross index and P-wave velocity measurements, was computed to detect the presence of fractures. After calibration, and under the assumption that the slower the P-wave velocity, the higher the permeability – porosity, a 3D seismic block of reflection can inform on preferential areas where flow should occur. At the scale of an open wellbore, acoustic loggings that measure wave velocities over a short distance within the well also inform on open features crosscut by the well. Finally, flow log measurements confirm the occurrence of flowing horizons that were previously marked by both seismic and acoustic data. Seismic and acoustic data are therefore suited to image contrasted hydraulic properties over fractured subsurface systems usually poorly documented.

Pliocene and Pleistocene stratigraphic evolution of the western Niger Delta intraslope basins: A record of glacio-eustatic sea-level and basin tectonic forcings

Although climate proxy (δ18O) across the world ocean basins reveals that orbital forcing significantly controlled the Pliocene and the Pleistocene sediment deposition, and has been demonstrated in seismic and outcrop studies on the continental shelves of many margins, few or no seismic stratigraphic studies have investigated orbital forcing on deep-water sediment records. In this study, we combined detailed seismic stratigraphy and 3D geomorphological analysis of a high-resolution 3D seismic block in a detailed study of the stratigraphic evolution of the western Niger Delta intraslope basins over the last 5.5 Ma. Two mega seismic units named MSU 1 and MSU 2 were identified. The change in sedimentary architecture from (i) mass flows and turbidite sequences to (ii) hemipelagic and turbidite sequences at the MSU 1/MSU 2 transition coincides with a significant (x3) increase in sedimentation rates and a transition from dominant 400 ka eccentricity cycles (from 5.3 Ma-0.8 Ma) to dominant 100 ka eccentricity cycles, at the Middle Pleistocene Transition (MPT) (circa 0.8‐–0 Ma). The timing of these changes was estimated based on a detailed analysis of seismic facies succession, correlation of seismic markers with high-resolution sea-level and oxygen isotope curves, and estimation of sequence duration. Further changes in the sedimentary record, characterised by turbidite-dominated sequences at the lower part of MSU 1 to mixed mass flows and turbidite sequences at the upper part of MSU 1, were respectively correlated with changes that occurred in the early Pliocene (circa 4.9 Ma) and in the early Pleistocene (circa 2.6 Ma). The depositional sequence on the western Niger Delta intraslope basin is usually characterised by a falling stage erosional surface (FSES) at its base and top (sequence boundary), and by (i) basal MTDs/bypass facies (where preserved), (ii) turbidite feeder channels/aggrading or meandering channel levee complexes and/or MTDs (slides/slumps) and (iii) hemipelagic drapes that successively document the falling stage, lowstand to early transgressive and late transgressive to highstand transits of the shoreline. The Pliocene and Pleistocene sedimentary records of the western Niger Delta intraslope basins were controlled by interplay between allocyclic forcing linked to glacio-eustatic sea-level oscillations and basin tectonics associated with mobile shale movements. .

Methods for Evaluating the Characteristics of the Stress-Strain State of Seismic Blocks Under Operating Conditions

The concept of the vibration and seismic isolation of heavy mining machines, buildings, and structures with rubber seismic blocks is considered. The concept of the seismic isolation of structures is very topical. In Japan, New Zealand, France, Greece, England, USA, and in a number of other countries, it is successfully used for the earthquake protection of such important structures as nuclear power stations, schools, bridges, museums, office and residential buildings. Seismic isolation systems including rubber blocks are most commonly used. The known publications in these countries do not present analytical calculations and technological peculiarities of manufacturing elements. In Ukraine, this concept was extended by developing seismic isolation blocks for the earthquake protection of residential buildings and vibration isolation blocks for the vibration protection of heavy equipment (weight of up to 300 t, used in Russia, Ukraine) and residential buildings. Results of static and dynamic tests of a parametric series of rubber seismic blocks for the vibration protection of residential buildings are presented. A pile design with anti-vibration rubber mounts is considered. Developed and tested rubber seismic block designs were used to protect against subway and motor vehicle induced vibrations two dwelling houses in Kiev (a ten-section ten-storey and a three-section 27-storey dwelling house) and three houses in Lvov. Vibration and seismic isolation with rubber seismic blocks provides a natural vibration frequency of building in the horizontal plane of under 1 Hz, which complies with the requirements of the state building codes and Eurocode 8 for the design of seismic isolation systems for buildings.

Earthquake Processes: A View from Synergetics and the Theory of Catastrophes

The theory of catastrophes and synergetics, developed by mathematicians in the second half of the twentieth century (Haken in Synergetics. Introduction and advances topics. Springer, Berlin, 1978; Arnol’d VI in Catastrophic theory. Springer, Berlin 2004), is used to analyze earthquake processes in active faults. It is shown that the oscillators of the seismic radiation are vibrating blocks at the border of the fault, and the source of the energy supply is the margin of the fault moving with the velocity V0. The input or loss of energy is regulated by a nonlinear element, the frictional force F(V), which depends on the difference V between the velocity of the fault margin V0 and the velocity of the seismic block vibration: V = V0 − dx/dt. Precise conditions for the occurrence of an earthquake, its attenuation, or the generation of a tectonic tremor in its source are formulated.

Seismic Cycles and Trend Predictions of Earthquakes in Sumatra–Andaman and Burmese Subduction Zones using Temporal b-value and Hurst Analysis

The annual b-value fluctuation patterns in Burmese subduction zone and Andaman–Sumatra subduction zone are evaluated from earthquake data (January 1990 to June 2016; Mw ³ 4.3) to identify seismic cycles with sequential dynamic phases as described in the ‘elastic failure model’ of Main et al. (1989). Two seismic cycles have been identified in Andaman–Sumatra subduction zone, one started in 1990 and ended on 2004 with occurrence of great Sumatra earthquake (Mw 9.0) and the other started in 2005 and continuing till date with the phase of crack coalescence and fluid diffusion (3A&B). Similarly, the subduction zone of Burma shows evidence of one incomplete seismic cycle within 1990–2016 and presently undergoing the crack coalescence and fluid diffusion (3A&B) phase. The analysis has prompted to subdivide the area into thirteen smaller seismic blocks (A to M) to analyse area specific seismic trend and vulnerability analysis employing Hurst Statistics. Hurst plots with the dynamic phases of ‘elastic failure model’ of earthquake generation is compared to assess the blocks with high seismic vulnerability. The analysis suggest that north Andaman zone (block G) and north Burma fold belt (block M) are seismically most vulnerable. Moreover, the seismic vulnerability of Tripura fold belt and Bangladesh plain (block K) is equally high.

Tectonic characteristics and distribution of Putaohua oil Reservoir in Changchang area of Songliao basin

Since the Late Jurassic in the Songliao Basin, the tectonic movement of Yanshan and Heshan has experienced a lot of tectonic movement. The tectonic activity has a clearer display on the seismic profile. The tectonic deformation is generally weak in the east, Features. The regional structure of the Chaochang area is located on the Chaoyangou terrace and Changchunling anticline belt in the central depression of the northern part of the Songliao Basin, and across the two tectonic units of the Chaoyanggou terrace and Changchunling anticline. The study area is characterized by a low tectonic pattern in the southwest and northwest. The highest point is located near the Chang72 well in the Changchunling anticline. The elevation is about -100 m, and the lowest point is the Zhou50 Well near the depth of about - 1750 m. Based on the technical means such as splicing, closed difference correction, horizon calibration, seismic interpretation and attribute extraction of 9 seismic blocks in the study area, the seismic interpretation of the top of the Putaohua reservoir is completed, and the next step Style, tectonic evolution characteristics, oil and gas accumulation law and other research work to lay the foundation.

REGIONAL CHARACTERISTICS OF STRESS STATE OF MAIN SEISMIC ACTIVE FAULTS IN MID‐NORTHERN PART OF SICHUAN‐YUNNAN BLOCK

AbstractWe restore the seismic source spectrums of 1012 earthquakes (2.0 ≤ ML ≤ 5.0) in the mid‐northern part of Sichuan‐Yunnan seismic block between January 1, 2009 and December 31, 2015, then calculate the source parameters (e.g., seismic moments M0, focal scale r and stress drop Δσ) and fit the calibration relationship between these parameters. Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units. For each unit the stress distribution characteristics, change of stress drop with location, correlation between the stress‐strain loading and the dynamic process of regional deformation, are discussed respectively. The results show that seismic moments M0 are consistent with the magnitude‐moment relation that lgM0 = 0.92ML + 10.46. The relationship between stress drop and magnitude is consistent with the result gained by Nuttli that intraplate earthquake follows the ISD model, with a statistical relationship lgΔσ = 0.31 lgM0 – 3.92.Seismic source stress drop results show the following, (1) The stress at the end of the Jinshajiang fault is low, the overall sliding rate of the fault unit is high, and strong earthquake activity is very rare. In the fault belt consisting of three secondary faults, stress‐strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2) Stress drop of Xianshuihe fault zone is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding‐Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garzê‐Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3) High stress‐drop events were concentrated on Anninghe‐Zemuhe fault zone, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4) On Lijiang‐Xiaojinhe fault zone, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply. Stress background in the Muli area is low and may be affected by the local tectonic environment. The study also shows that, (1) Stress drops display a systematic change with different faults and locations, high stress‐drop events occur mostly in the fault intersection area. Faults without locking condition and mainly creeping are mainly characterized by low stress drop. (2) Contrasting to what is commonly thought that “strike‐slip faults are not easy to accumulate stress”, Xianshuihe fault zone and Anninghe‐Zemuhe fault zone all exhibit high stress levels, which may be due to that the magnitude and intensity of medium‐strong earthquakes are not enough to release the accumulated energy. On the other hand, in the complex dynamics of regional deformation, when the tectonic force blocking fault movement and its contribution to accumulation of stress plays a key role, the earthquake of same magnitude will release higher stress drop.

Repeated fluid expulsions during events of rapid sea-level rise in the Gulf of Lion, western Mediterranean Sea

Based on a High-Resolution 3D seismic block acquired in the Gulf of Lion in 2004–2005 we investigated fluid pipes and pockmarks on the top of the interfluve between the Hérault canyon and the Bourcart canyon both created by turbidity currents and gravity flows from the shelf to the deep basin in the north-western Mediterranean Sea. Combining the geometry of the potential fluid pipes with the induced deformation of surrounding sediments leads then to the ability to differentiate between potential fluid sources (rootvssource) and to better estimate the triggering mechanisms (allochtonousvs.autochtonous cause). We linked together a set of derived attributes, such as Chaos and RMS amplitude, to a 3D description of pipes along which fluids may migrate. As previously shown in other basins, the induced deformation, creating cone in cone or V-shaped structures, may develop in response to the fluid pipe propagation in unconsolidated sediments in the near surface. The level at the top of a cone structure is diachronous. It means that stratigraphic levels over this surface are deformed at the end of the migration. They collapse forming a depression called a pockmark. These pipes are the result of repeated cycles of fluid expulsion that might be correlated with rapid sea-level rise instead of sediment loading. The most recent event (MIS 2.2 stage) has led to the formation of a pockmark on the modern seafloor. It has been used as a reference for calculating the effect of a rapid sea-level rise on fluid expulsion. As all physical and geometrical parameters are constrained, we were able to define that a + 34 m of sea level rise may account for triggering fluid expulsion from a very shallow silty-sandy layer at 9 m below seafloor since the last glacial stage. This value is consistent with a sea level rise of about 102 m during this period. This study shows that the episodic nature of fluid release resulted from hydromechanical processes during sea-level rise due to the interactivity between high pressure regimes and principalin situstresses.

Marked point processes for enhancing seismic fault patterns

In this paper we present a new method for fault extraction in seismic blocks, using marked point processes. Our goal is to increase the detection accuracy of the state of the art fault attributes by computing them on a system of objects based on an a priori knowledge about the faults.An original curved support has been developed to describe the faults in vertical sections of the seismic blocks. The results are compared with the previous models used for linear network extraction, such as the Candy model. Synthetic blocks were used to compare the results obtained thanks to the point processes with the classical attributes.To segment the whole blocks, a multi-2D approach was used. Several modifications of the algorithm were necessary in order to make the results easier to interpret for geologists.One interest of the high-level approach offered by the marked point processes is the possibility of using the objects as a common support for various fault detection operators. A whole detection framework can be proposed which acts like a decision fusion process.

Crustal architecture and tectono-magmatic history of the western offshore of India: Implications on deepwater sub-basalt hydrocarbon exploration

Abstract The western continental margin of India (WCMI) has evolved as a result of two-stage rifting and breakup events, the first one between India and Madagascar during the mid Cretaceous, and the second event between India and Seychelles during the late Cretaceous. Detailed seismic studies by earlier workers in the offshore margin confirm that it is a poly-rift margin with significant volcanic emplacements, and on the basis of these datasets; the western margin was classified as volcanic. In the present study, constrained potential field modeling of four profiles across the western offshore region revealed that the eastern basin comprising of Laxmi and Laccadive basins as well as the adjoining Laxmi and the Laccadive ridges are underlain by the extended continental crust and has been punctured by several magmatic intrusions. The models further suggest that the continent–ocean boundary (COB) lies to the west of Laccadive and Laxmi ridges, and also in the southern part of Laccadive basin. In this paper, we presented high-resolution seismic images at the margin that have revealed the presence of deeper sedimentary strata below the K/T flood-basalts and provided detailed interpretation of few sections belonging to a 3D seismic block in the deepwater Kerala–Konkan offshore. The sections reveal numerous features such as the sag basin, fractures, faults and folding below the basaltic top. Further, significant sedimentary wedges terminating against the volcanic highs are inferred to be the Mesozoic sub-basalt plays. The interpreted crustal transects, the inferred combination of tectono-magmatic processes and the probable occurrence of sub-basalt sediments at the margin are analyzed and encapsulated to provide a basis for assessing deepwater petroleum prospectivity of the entire western margin offshore.

Seismic geomorphology of early North Atlantic sediment waves, offshore northwest Africa

The lower continental rise of Morocco’s Atlantic Margin contains three varying morphologies of buried deepwater sediment waves. The 3D mapping of a [Formula: see text] seismic survey acquired in the Safi Haute Mer seismic block revealed numerous linear features that range from small, less than 17-m-thick Jurassic-age amplitude striations up to 110-m-thick migrating Cretaceous contourite sediment waves. Early proto-Atlantic deposition in Safi Haute Mer initiated in the Triassic, with syn- and postrift accumulation in basement half-grabens basinward of the modern Moroccan salt front. Sedimentation continued through the Mesozoic with deposition of turbidites, progradation of clinoforms, and culminating in multiple Late Cretaceous, regionally expansive, mass-transport deposits ([Formula: see text]). Tertiary stratigraphy consists of multiple thin, pelagic drapes and unconformities. The complex history of sedimentation and tectonics gave rise to three styles of sediment waves found within the study area: (1) type J1 — small and poorly imaged, Jurassic age, locally generated wave forms that have wavelengths of up to 12 km and crest-to-crest separations of less than 1 km with little or no vertical expression; (2) type K1 — early Aptian constructional sediment waves ([Formula: see text] thick) built by contour currents that traveled in and near a contourite moat at the base of a seafloor high produced by shallowly buried mobile salt; and (3) type K2 — latest Albian and earliest post-Albian sediment waves built by along-slope currents on a relatively stable slope, showing evidence of updip migration. The type K2 sediment wavefield exhibits wave heights of 40 m and crest-to-crest separations of 1 km, and it is continuous over the entire study area.

Role of Transverse Tectonics in the Himalayan Collision: Further Evidences from Two Contemporary Earthquakes

Abstract: Two contemporary earthquakes originating in the central Himalayan arc and its foredeep (Sikkim earthquake of 18.09.2011, Mw 6.9, h: 10-60 (?) km and Bihar-Nepal earthquake of 20.08.1988, Mw 6.8, h: 57 km) are commonly associated with transverse lineaments/faults traversing the region. Such lineaments/faults form active seismic blocks defining promontories for the advancing Indian Craton. These actually produce conjugate shear faulting pattern suggestive of pervasive crustal interplay deep inside the mountains. Focal mechanism solutions allow inferring that large part of the current convergence across the central Himalayan arc is accommodated by lateral slip. Similar slip also continues unabated in the densely populated foredeep for distances up to several tens of kilometers south of the Main Boundary Thrust (MBT).

Geometry and chronology of late Quaternary depositional sequences in the Eastern Niger Submarine Delta

On seismic profiles, the Eastern Niger Submarine Delta displays spectacular prograding wedges separated by discontinuities on the continental shelf and correlative conformities seawards. In spite of the numerous studies focused on deep oil reservoirs in this area, and because of the presence of pronounced syndepositional deformation, the detailed geometry and chronology of the Quaternary succession has been neglected, while it contains relevant information about sedimentary processes and the factors controlling sediment depocenters, presence of fluids and sediment deformation.This study provides the first comprehensive view of the Late Quaternary stratigraphic architecture of the Eastern Submarine Niger Delta. The stratigraphic interpretation is based on: (1) a seismic dataset composed of 2D seismic profiles with variable resolution (Sparker, Chirp) and four 3D seismic blocks (short offset processing); and (2) in situ measurements and samples (3 Calypso and 2 Stacor long piston cores). The correlation of seismic reflectors with chronological information from long piston cores (δ18O values and XRF-derived Ca profiles), shows that the upper-most 5 depositional sequences formed during the last ca. 500 kyr BP, in response to glacial/interglacial fluctuations driven by 100-kyr Milankovitch cycles and the subsidence rate for the late Quaternary period are around 300m/Myr. The prograding wedges at the shelf break have distinct seismic facies with high-angle clinoforms building regional scale depositional sequences locally disrupted by growth faults. Although highly influenced by syndepositional deformation with thick accumulation in the hanging walls of growth faults, the main depositional sequence pattern is tuned with glacio-eustatic oscillations and the high-angle clinoforms near the shelf edge correspond to upper shorefaces/delta fronts or subaqueous deltas formed during glacial lowstand periods. The largest Mass Transport Complex in this zone is interpreted as resulting from oversteepening of the shelf edge during MIS 10.

Choosing parameters of design elements of an impulse seismic source

Based on the analysis of actuation of an impulse seismic source, the formulas are presented for calculating the motor impulse stroke length, and weights of the seismic vibrator and swamp block, that can be used in the seismic source designing.

Numerical Analysis of JNES Seismic Tests on Degraded Combined Piping System

Nuclear power plant safety under seismic conditions is an important consideration. The piping systems may have some defects caused by fatigue, stress corrosion cracking, etc., in aged plants. These cracks may not only affect the seismic response but also grow and break through causing loss of coolant. Therefore, an evaluation method needs to be developed to predict crack growth behavior under seismic excitation. This paper describes efforts conducted to analyze and better understand a series of degraded pipe tests under seismic loading that was conducted by Japan Nuclear Energy Safety Organization (JNES). A special “cracked-pipe element” (CPE) concept, where the element represented the global moment-rotation response due to the crack, was developed. This approach was developed to significantly simplify the dynamic finite element analysis in fracture mechanics fields. In this paper, model validation was conducted by comparisons with a series of pipe tests with circumferential through-wall and surface cracks under different excitation conditions. These analyses showed that reasonably accurate predictions could be made using the abaqus connector element to model the complete transition of a circumferential surface crack to a through-wall crack under cyclic dynamic loading. The JNES primary loop recirculation piping test was analyzed in detail. This combined-component test had three crack locations and multiple applied simulated seismic block loadings. Comparisons were also made between the ABAQUS finite element (FE) analyses results to the measured displacements in the experiment. Good agreement was obtained, and it was confirmed that the simplified modeling is applicable to a seismic analysis for a cracked pipe on the basis of fracture mechanics. Pipe system leakage did occur in the JNES tests. The analytical predictions using the CPE approach did not predict leakage, suggesting that cyclic ductile tearing with large-scale plasticity was not the crack growth mode for the acceleration excitations considered here. Hence, the leakage was caused by low-cycle fatigue with small-scale yielding. The procedure used to make predictions of low-cycle fatigue crack growth with small-scale yielding was based on the Dowling ΔJ procedure, which is an extension of linear-elastic fatigue crack growth methodology into the nonlinear plasticity region. The predicted moments from the CPE approach were used using a cycle-by-cycle crack growth procedure. The predictions compare quite well with the experimental measurements.