Seismic Environment Research Articles

Code-Oriented Damage Assessment for Buildings

In this study, we present a simple framework for the evaluation of the cost to repair building damage using engineering parameters related to current seismic building codes. Specifically, we envision relationships for building damage repair cost as a function of ground shaking spectral acceleration (Sa at structural period, T), design base shear coefficient (V/W), response modification factor (R), height, and framing system. This framework provides a flexible system for collecting and evaluating building damage from ground shaking, improving the building code, and predicting earthquake damage repair costs to new or existing, or retrofitted buildings, in a wide variety of seismic environments. In the absence of comprehensive statistical earthquake damage data, we resample the ATC-13 damage database to calibrate an initial damage model. We call the model CODA, for Code-Oriented Damage Assessment for Buildings.

Short-Period Seismic Noise in Vorkuta, Russia

Cultural development of new subpolar areas in Russia is associated with a need for detailed seismic research; for example, mapping of regional seismicity and seismic monitoring of specific mining enterprises. Of special interest are the northern territories of European Russia, including shelves of the Kara and Barents seas, Yamal Peninsula, and the Timan-Pechora region. Continuous seismic studies of these territories are important because there is insufficient seismological knowledge of the area and an absence of systematic data on the regional seismicity. Another timely task is to consider the seismic environment in the design, construction, and operation of natural gas extracting enterprises such as the construction of the North European Gas Pipeline. Issues of scientific importance underlying seismic studies in the region are the complex geodynamical setting, the presence of permafrost, and the complex tectonic structure. In particular, the Uralian Orogene (Figure 1) strongly affects the propagation of seismic waves. The existing subpolar seismic stations in Russia (APA at 67,57°N, 33,40°E; LVZ at 67,90°N, 34,65°E; and NRIL at 69,50°N, 88,40°E) do not cover the extensive area between the Pechora and Ob' rivers (Figure 1). Thus seismic observations in the Vorkuta area, which lies within the area of concern, represent a special interest. Continuous recording at a seismic station near the city of Vorkuta (67,50°N, 64,11°E) has been conducted since 2005 for the purpose of regional seismic monitoring and, more specifically, detection of seismic signals caused by local mining enterprises (Adushkin et al. 2007). Current surveys of local seismic noise are particularly aimed at a technical survey for the suitability of the site for installation of a small-aperture seismic array, which would include 10–12 recording instruments, with the Vorkuta seismic station as the central element (Okada 2003; Peterson 1993; Spivak and Kishkina 2004; Stutzmann et al. 2000). When …

An experimental investigation on liquefaction potential and post-liquefaction shear strength of impounded fly ash

Liquefaction resistance and post-liquefaction shear strength of impounded Class F fly ash are investigated using laboratory experiments. The study was aimed to evaluate liquefaction potential of a 45 ha impoundment proposed as a base for a utility monofill. The evaluation included cyclic triaxial tests performed on reconstituted fly ash specimens with various densities at different confining stresses and cyclic stress ratios representative of the impounded material and the seismic environment. The results are presented in the form of design charts. Post-liquefaction strengths were measured by reconsolidating the specimens at the initial effective confining stress and performing consolidated undrained triaxial tests. The measured cyclic strength was compared with the seismically induced stresses in the profile using a one-dimensional wave propagation method. The cyclic loadings imposed on the ash by the design earthquakes were found to be lower than the measured cyclic strength of the material. The post liquefaction shear strengths showed some scatter; however, they were typically higher than the initial shear strengths before exposure of the material to cyclic load.

Centrifuge Modeling of Rock-Fill Embankments on Deep Loose Saturated Sand Deposits Subjected to Earthquakes

Rockfill is commonly used for construction of artificial islands, breakwaters, jetties, quay walls, coastal defenses, protective barriers for reclaimed land, and even as ship impact protection structures around bridge piers. The economic construction method often involves rock dumping onto loose or liquefiable sediments with little or no ground improvement. Hence in a seismic environment, these rock-fill or rubble mound structures are potentially vulnerable to failure due to pore pressure generation effects of the underlying deposits. This paper presents experimental investigation carried out using dynamic centrifuge modeling to study the seismic performance of rock-fill or rubble mound embankment structures on liquefiable sand deposits. The centrifuge test results indicate that the rock-fill embankments suffer substantial settlement owing to rock-fill penetration into the founding sand deposit assisted by the pore pressure generation effects. This mechanism of failure was not, however, observed for a sand embankment where the particle size distribution is comparable to the foundation. This result has important implications in the design methodologies adopted for rock-fill or rubble mound structures.

Seismic parameters characterization at Texcoco lake, Mexico

Texcoco lake area, in the Valley of Mexico, presents particularly difficult geotechnical conditions due to the presence of thick deposits of soft, highly compressible lacustrine clay, randomly interbeded with sand lenses. In contrast to other sites in the valley, there is a lack of information regarding the geotechnical subsoil conditions, dynamic properties, and earthquake recordings at rock sites. Thus, the seismic environment is not completely identified. This paper describes field and laboratory investigations as well as analytical studies, aimed at characterizing the ground response of a particular site located in this region, where is planed to be built an strategic power station, which will be the driving force for the urban and industrial development of Mexico City northeast side. In situ measurements of shear wave velocity, using suspension PS logging, along with cone penetration, CPT, and standard penetration, SPT, resistance values, and results from series of resonant column and cyclic triaxial tests were used to obtain a 3-D representation of the subsoil characteristics found at the site, and the variation of dynamic properties with strain level. Predicted shear wave velocity profiles derived through empirical correlations compared well with measured values. Ground motion definition was achieved indirectly through empirically derived response spectra obtained from sets of earthquake ground motions recorded at a nearby station located in soft soil. Acceleration time histories representative of the design earthquake were obtained using time-domain spectral matching. 1-D shear wave deconvolution was used to obtain the corresponding ground motions in rock.

Wild African elephants (Loxodonta africana) discriminate between familiar and unfamiliar conspecific seismic alarm calls

The ability to discriminate between call types and callers as well as more subtle information about the importance of a call has been documented in a range of species. This type of discrimination is also important in the vibrotactile environment for species that communicate via vibrations. It has recently been shown that African elephants (Loxodonta africana) can detect seismic cues, but it is not known whether they discriminate seismic information from noise. In a series of experiments, familiar and unfamiliar alarm calls were transmitted seismically to wild African elephant family groups. Elephants respond significantly to the alarm calls of familiar herds (p=0.004) but not to the unfamiliar calls and two different controls, thus demonstrating the ability of elephants to discriminate subtle differences between seismic calls given in the same context. If elephants use the seismic environment to detect and discriminate between conspecific calls, based on the familiarity of the caller or some other physical property, they may be using the ground as a very sophisticated sounding board.

Seismic vulnerability estimation of the building considering seismic environment and local site condition

A procedure is developed to incorporate seismic environment and site condition into the framework of seismic vulnerability estimation of building to consider the effects of the severity and/or frequency content of ground motion due to seismic environment and site condition. Localized damage distribution can be strongly influenced by seismic environment and surficial soil conditions and any attempt to quantify seismic vulnerability of building should consider the impact of these effects. The seismic environment, site and structure are coupled to estimate damage probability distribution among different damage states for the building. Response spectra at rock site are estimated by probabilistic seismic hazard assessment approach. Based upon engineering representations of soil and amplifying spectral coordinates, frequency content and severity of ground motion are considered. Furthermore the impacts of severity and/or frequency of ground motion effects are considered to estimate the seismic response of reinforced concrete building and damage probability distribution for the building. In addition, a new method for presenting the distribution of damage is developed to express damage probability distribution for the building for different seismic hazard levels.

DEMETER HIGH RESOLUTION 3D SEISMIC SURVEY—REVITALISED DEVELOPMENT AND EXPLORATION ON THE NORTH WEST SHELF, AUSTRALIA

The newly acquired 3,590 km2 Demeter 3D high resolution seismic survey covers most of the North West Shelf Venture (NWSV) area; a prolific hydrocarbon province with ultimate recoverable reserves of greater than 30 Tcf gas and 1.5 billion bbls of oil and natural gas liquids. The exploration and development of this area has evolved in parallel with the advent of new technologies, maturing into the present phase of revitalised development and exploration based on the Demeter 3D.The NWSV is entering a period of growing gas market demand and infrastructure expansion, combined with a more diverse and mature supply portfolio of offshore fields. A sequence of satellite fields will require optimised development over the next 5–10 years, with a large number of wells to be drilled.The NWSV area is acknowledged to be a complex seismic environment that, until recently, was imaged by a patchwork of eight vintage (1981–98) 3D seismic surveys, each acquired with different parameters. With most of the clearly defined structural highs drilled, exploration success in recent years has been modest. This is due primarily to severe seismic multiple contamination masking the more subtle and deeper exploration prospects. The poor quality and low resolution of vintage seismic data has also impeded reservoir characterisation and sub-surface modelling. These sub-surface uncertainties, together with the large planned expenditure associated with forthcoming development, justified the need for the Demeter leading edge 3D seismic acquisition and processing techniques to underpin field development planning and reserves evaluations.The objective of the Demeter 3D survey was to re-image the NWSV area with a single acquisition and processing sequence to reduce multiple contamination and improve imaging of intra-reservoir architecture. Single source (133 nominal fold), shallow solid streamer acquisition combined with five stages of demultiple and detailed velocity analysis are considered key components of Demeter.The final Demeter volumes were delivered early 2005 and already some benefits of the higher resolution data have been realised, exemplified in the following:Successful drilling of development wells on the Wanaea, Lambert and Hermes oil fields and identification of further opportunities on Wanaea-Cossack and Lambert- Hermes;Dramatic improvements in seismic data quality observed at the giant Perseus gas field helping define seven development well locations;Considerably improved definition of fluvial channel architecture in the south of the Goodwyn gas field allowing for improved well placement and understanding of reservoir distribution;Identification of new exploration prospects and reevaluation of the existing prospect portfolio. Although the Demeter data set has given significant bandwidth needed for this revitalised phase of exploration and development, there remain areas that still suffer from poor seismic imaging, providing challenges for the future application of new technologies.

Mapping of thin sandy aquifers by using high resolution reflection seismics and 2-D electrical tomography

Electrical tomography, which gives good results even in fairly complex geological environments, has given a new lease of life to electrical methods in hydrogeological surveys. Nevertheless, a rapid decline in resolution with increasing depth remains the main problem of the electrical methods. In the Pannonian basin in Croatia, at a test area, combining both electrical tomography and seismic reflection methods provides data that better constrain the lithological and hydrogeological model of the subsurface. Electrical tomography revealed a rather thick packet of sediments with increased resistivity at depths of 40–100 m. Using the electrical forward modelling, the existence of two different hydrogeological models was shown. The first model presupposes a reasonably homogeneous packet of sandy clays or clayey sands, and the other model presupposes the alternation between layers of clays and sands. From the hydrogeological point of view, the second model is perspective, but unfortunately, the use of electrical tomography alone does not allow the ambiguity to be resolved. The separation of these two models became possible using seismic reflection. Three seismic environments were isolated from the seismic profile treated, and the strongest reflections were discovered in the first seismic environment, which covers the depths from 40 to 100 m. It was determined that the second model is more acceptable, because these reflections are caused by lithological changes, that is, the alternations of sands and clays. The interpretation is consistent with exploratory borehole data. The conclusion is that electrical tomography gives data concerning the sediment lithology up to depths of 40 m, but at greater depths combined interpretation of electrical and seismic data constrains the subsurface model better.

Evolutionary aseismic design and retrofit of structures with passive energy dissipation

A new computational framework is developed for the design and retrofit of building structures by considering aseismic design as a complex adaptive process. For the initial phase of the development within this framework, genetic algorithms are employed for the discrete optimization of passively damped structural systems. The passive elements may include metallic plate dampers, viscous fluid dampers and viscoelastic solid dampers. The primary objective is to determine robust designs, including both the non-linearity of the structural system and the uncertainty of the seismic environment. Within the present paper, this computational design approach is applied to a series of model problems, involving sizing and placement of passive dampers for energy dissipation. In order to facilitate our investigations and provide a baseline for further study, we introduce several simplifications for these initial examples. In particular, we employ deterministic lumped parameter structural models, memoryless fitness function definitions and hypothetical seismic environments. Despite these restrictions, some interesting results are obtained from the simulations and we are able to gain an understanding of the potential for the proposed evolutionary aseismic design methodology. Copyright © 2005 John Wiley & Sons, Ltd.

Long-term study of the seismic environment at LIGO

The LIGO experiment aims to detect and study gravitational waves using ground-based laser interferometry. A critical factor to the performance of the interferometers, and a major consideration in the design of possible future upgrades, is isolation of the interferometer optics from seismic noise. We present the results of a detailed programme of measurements of the seismic environment surrounding the LIGO interferometers. We describe the experimental configuration used to collect the data, which were acquired over a 613 day period. The measurements focused on the frequency range 0.1–10 Hz, in which the secondary microseismic peak and noise due to human activity in the vicinity of the detectors was found to be particularly critical to the interferometer performance. We compare the statistical distribution of the data sets from the two interferometer sites, construct amplitude spectral densities of seismic noise amplitude fluctuations with periods of up to 3 months and analyse the data for any long-term trends in the amplitude of seismic noise in this critical frequency range.

Implementation of electrostatic actuators for suspended test mass control

We present our findings on recent experiments involving the use of electrostatic actuators for control of test masses suspended by flexure membranes. The actuator design and its proposed implementation for AIGO are described. With the use of first generation DSP controllers developed at VIRGO, we demonstrate the successful control of the tilt of a suspended dummy test mass in a typical seismic environment. Problems of the coupling of translation and tilt modes in a niobium flexure suspended test mass are discussed and possible solutions are presented.

Finite element model for the probabilistic seismic response of heterogeneous soil profile

This paper deals with the numerical simulation of heterogeneous soil profile and its behavior under uniform seismic environment. Soil properties of interest are shear modulus, fraction of critical damping and Poisson ratio, modeled as spatially random fields. Shear modulus is modeled using the lognormal distribution, which enables analyzing its large variability. Because fraction of critical damping and soil Poisson ratio are bounded in practice between two extreme values, their random fields are obtained from the Beta distribution, where the Beta field is determined, by performing a mapping technique on the lognormal probability distribution function diagram. In this frame, the seismic response is carried out via Monte Carlo simulations combined with deterministic finite element method. Also, the performance of two approximate techniques, using stationary stochastic process tools, and accounting for the nonstationnarity in an implicit way, are investigated for the purpose to determine statistics of extreme ground surface acceleration. It is found that both techniques are not appropriate for determining the statistics of a highly heterogeneous medium. The analysis integrates the influence of, coefficient of variation of the three soil properties, the inter-property correlation coefficients, as well as horizontal and vertical correlation lengths. Results of this analysis indicate that heterogeneity highly influences the behavior of the soil profile which induces differential movement at ground surface and makes evident the filtering effect of frequencies, making hence the simulated soil softer. Obtained results indicate that a positive correlation between shear modulus and fraction of critical damping favors seismic wave amplification, and that shear modulus and fraction of critical damping are of prime importance. So, Poisson ratio variability can be neglected in a dynamic analysis of a soil profile.

Demarcation of potential seismic sources on integration of genetic algorithm and BP algorithm

In this paper potential seismic sources in coastal region of South China are identified by integration of genetic algorithm (GA) and back propagation (BP algorithm). GA is used for finding the best parameter combination rapidly in an infinite solution space for artificial neural networks (ANN). The results show that the distribution of potential seismic sources with different upper magnitude demarcated by this classifier is mostly satisfied the intrinsic relationship between seismic environment and earthquake occurrence, with less effect from subjective judgment of human being.

Mitigation of lateral ground displacements of liquefied soils with underground barriers

Analyses of damage data from earthquakes in the last 35 years show that very high financial losses have resulted from cases where liquefaction of soils was associated with ground lateral displacements towards a free boundary such as a shoreline, a river channel, or an open trench. Lateral displacements in excess of 10 m have been documented in the literature [Bartlett and Youd, J. Geotech. Engng, ASCE 121 (1995) 316]. In fact, in many cases, displacements amounting to only a fraction of this number are capable of causing considerable disruption to man-made works. Several factors contribute to the extent of lateral spreading: surface and subsurface geometry, soil characteristics, and intensity of ground motion. Ground displacements can be minimized or even arrested in practice with an underground structure properly designed to counter the driving forces, gravity and inertia combined. Mitchell et al. suggested practical guidance for the design of such structures, or barriers, in 1998 [Geotech. Spec. Publ. 75 (1998) 580]. However, to date there is no standard procedure to carry out the analysis of such barriers. The paper describes several recent designs of underground barriers that have been constructed in highly seismic environments. Three types of underground barriers are described: clay fill, a grid of structural piles, and a grid of cement-treated soil. The design of the cement-treated cell barrier is discussed in detail as it accounts for the most unfavorable combination of all forces acting on the structure: lateral stresses induced by liquefied soil, hydrodynamic effects, inertia forces, and loss of ground.

Exploring the Potential Use of Seismic Waves as a Communication Channel by Elephants and Other Large Mammals1

Bioseismic studies have previously documented the use of seismic stimuli as a method of communication in arthropods and small mammals. Seismic signals are used to communicate intraspecifically in many capacities such as mate finding, spacing, warning, resource assessing, and in group cohesion. Seismic signals are also used in interspecific mutualism and as a deterrent to predators. Although bioseismics is a significant mode of communication that is well documented for relatively small vertebrates, the potential for seismic communication has been all but ignored in large mammals. In this paper, we describe two modes of producing seismic waves with the potential for long distance transmission: 1) locomotion by animals causing percussion on the ground and 2) acoustic, seismic-evoking sounds that couple with the ground. We present recordings of several mammals, including lions, rhinoceroses, and elephants, showing that they generate similar acoustic and seismic vibrations. These large animals that produce high amplitude vocalizations are the most likely to produce seismic vibrations that propagate long distances. The elephant seems to be the most likely candidate to engage in long distance seismic communication due to its size and its high amplitude, low frequency, relatively monotonic vocalizations that propagate in the ground and have the potential to travel long distances. We review particular anatomical features of the elephant that would facilitate the detection of seismic waves. We also assess low frequency sounds in the environment such as thunder and the likelihood of seismic transmission. In addition, we present the potential role of seismic stimuli in human communication as well as the impact of modern anthropogenic effects on the seismic environment.

Deterministic vs. probabilistic earthquake hazards and risks

Both probabilistic and deterministic methods have a role in seismic hazard and risk analyses performed for decision-making purposes. These two methods can complement one another to provide additional insights to the seismic hazard or risk problem. One method will have priority over the other, depending on how quantitative are the decisions to be made, depending on the seismic environment, and depending on the scope of the project (single site or a region). In many applications a recursive analysis, where deterministic interpretations are triggered by probabilistic results and vice versa, will give the greatest insight and allow the most informed decisions to be made.

Geotechnical factors in seismic design of foundations state-of-the-art report

This paper revises the factors that influence the behavior of foundations in seismic environments. It discusses aspects related with seismic load definition, dynamic soil properties, field and laboratory testing equipment, geoseismic instrumentation of prototypes, foundation seismic stability, use of artificial intelligence, among others. It also points out areas where more research is needed to better our knowledge on the physics of the problem and to improve experimental and numerical techniques, with the purpose of making more reliable and less costly foundation systems.

Response spectral relationships for rock sites derived from the component attenuation model

The seismological model was developed initially from the fundamental relationship between earthquake ground motion properties and the seismic moment generated at the source of the earthquake. Following two decades of continuous seismological research in the United States, seismological models which realistically account for both the source and path effects on the seismic shear waves have been developed and their accuracy rigorously verified (particularly in the long and medium period ranges). An important finding from the seismological research by Atkinson and Boore and their co-investigators is the similarity of the average frequency characteristics of seismic waves generated at the source between the seemingly very different seismic environments of Eastern and Western North America (ENA and WNA, respectively). A generic definition of the average source properties of earthquakes has therefore been postulated, referred to herein as the generic source model. Further, the generic ‘hard rock’ crustal model which is characteristic of ENA and the generic ‘rock’ crustal model characteristic of WNA have been developed to combine with the generic source model, hence enabling simulations to be made of the important path-related modifications to ground motions arising from different types of crustal rock materials. It has been found that the anelastic contribution to whole path attenuation is consistent between the ENA and WNA models, for earthquake ground motions (response spectral velocities and displacements) in the near and medium fields, indicating that differences in the ENA and WNA motions arise principally from the other forms of path-related modifications, namely the mid-crust amplification and the combined effect of the upper-crust amplification and attenuation, both of which are significant only for the generic WNA ‘rock’ earthquake ground motions. This paper aims to demonstrate the effective utilization of the latest seismological model, comprising the generic source and crustal models, to develop a response spectral attenuation model for direct engineering applications. The developed attenuation model also comprises a source factor and several crustal (wave-path modification) component factors, and thus has also been termed herein the component attenuation model (CAM). Generic attenuation relationships in CAM, which embrace both ENA and WNA conditions, have been developed using stochastic simulations. The crustal classification of a region outside North America can be based upon regional seismological and geological information. CAM is particularly useful for areas where local strong motion data are lacking for satisfactory empirical modelling. In the companion paper entitled ‘response spectrum modelling for rock sites in low and moderate seismicity regions combining velocity, displacement and acceleration predictions’, the CAM procedure has been incorporated into a response spectrum model which can be used to effectively define the seismic hazard of bedrock sites in low and moderate seismicity regions. This paper and the companion paper constitute the basis of a long-term objective of the authors, to develop and effectively utilize the seismological model for engineering applications worldwide.

Monitoring and education help seismic crew protect environment in transition‐zone survey

A program based on active monitoring and education helped Western Geophysical late last year complete a large speculative 3-D seismic survey in a sensitive Louisiana transition zone without creating the need for environmental remediation. Environmental authorities praised the program for, among other things, enabling Western Geophysical to discover a rookery of the endangered mottled duck and avoid disturbing it. The company has decided to use the program in all transition‐zone surveys in the southeastern United States.