Seismic Risk Studies Research Articles

State-of-the-art of historical earthquake research in Fennoscandia and the Baltic Republics

We review historical earthquake research in Northern Europe. 'Historical' is defined as being identical with seismic events occurring in the pre-instrumental and early instrumental periods between 1073 and the mid-1960s. The first seismographs in this region were installed in Uppsala, Sweden and Bergen, Norway in 1904-1905, but these mechanical pendulum instruments were broad band and amplification factors were modest at around 500. Until the 1960s few modern short period electromagnetic seismographs were deployed. Scientific earthquake studies in this region began during the first decades of the 1800s, while the systematic use of macroseismic questionnaires commenced at the end of that century. Basic research efforts have vigorously been pursued from the 1970s onwards because of the mandatory seismic risk studies for commissioning nuclear power plants in Sweden, Finland, NW Russia, Kola and installations of huge oil platforms in the North Sea. The most comprehensive earthquake database currently available for Northern Europe is the FENCAT catalogue covering about six centuries and representing the accumulation of work conducted by many scientists during the last 200 years. This catalogue is given in parametric form, while original macroseismic observations and intensity maps for the largest earthquakes can be found in various national publications, often in local languages. No database giving intensity data points exists in computerized form for the region. The FENCAT catalogue still contains some spurious events of various kinds but more serious are some recent claims that some of the presumed largest historical earthquakes have been assigned too large magnitude values, which would have implications for earthquake hazard levels implemented in national building codes. We discuss future cooperative measures such as establishing macroseismic data archives as a means for promoting further research on historical earthquakes in Northern Europe.

Seismic collapse risk of precast industrial buildings with strong connections

AbstractA systematic seismic risk study has been performed on some typical precast industrial buildings that consists of assemblages of cantilever columns with high shear‐span ratios connected to an essentially rigid roof system with strong pinned connections. These buildings were designed according to the requirements of Eurocode 8. The numerical models and procedures were modified in order to address the particular characteristics of the analyzed system. They were also verified by pseudo‐dynamic and cyclic tests of full‐scale large buildings. The intensity measure (IM)‐based solution strategy described in the PEER methodology was used to estimate the seismic collapse risk in terms of peak ground acceleration capacity and the probability of exceeding the global collapse limit state. The effect of the uncertainty in the model parameters on the dispersion of collapse capacity was investigated in depth. Reasonable seismic safety (as proposed by the Joint Committee on Structural Safety) was demonstrated for all the regular single‐storey precast industrial buildings addressed in this study. However, if the flexural strength required by EC8 was exactly matched, and the additional strength, which results from minimum longitudinal reinforcement, was disregarded as well as large dispersion in records was considered, the seismic risk might in some cases exceed the acceptable limits. Copyright © 2009 John Wiley & Sons, Ltd.

Near‐station topographic masses correction for high‐accuracy gravimetric prospecting

ABSTRACTThe expanding role of gravity prospecting in mineral and hydrocarbon exploration as well as seismic and volcanic risk studies will be related to its ability to provide high‐resolution anomalies. To achieve this goal it is necessary to consider the errors resulting from the topographic corrections, in particular near‐station effects. Such errors are relevant not only for severe topographies but also for relatively flat surfaces involving microgravity applications and large‐scale surveys.Indeed, the errors introduced by low‐resolution digital elevation models can be of the same order of magnitude as the anomalies of interest. This basic fact is demonstrated by tests on synthetic models. The results of this analysis are summarized in an intuitive graph that can be used to estimate what near‐station topographic resolution is necessary for a specific survey. For the Vulcano Island test site (in Southern Italy), we also compare results obtained using three different representations of the topographic surface with different horizontal resolutions and vertical precisions: one from existing photogrammetric data, the second from a digitized map and the third from a very high‐resolution laser scanning system. Among the three methods, laser scanning is shown to obtain the highest resolution topographic reconstructions in the shortest time. Some weaknesses of the laser scanning methodology are discussed and we suggest ways of overcoming them.

Cyclic response of slender RC columns typical of precast industrial buildings

The cyclic behaviour of slender cantilever columns in full-scale models of precast industrial buildings, designed by Eurocode 8, was studied experimentally and analytically. The shear span ratio of the columns was 12.5, which is more than allowed by Eurocode 8 for columns in frame structures (10). High deformability and a large deformation capacity (8%~drift) of the columns was observed. A lumped plasticity model was used in the analysis. In the paper the observed behaviour of the models has been compared with the predicted behaviour obtained by several empirically based models and procedures. It was observed that these models, which were developed for much lower shear span ratios (2–6), were not applicable for the analyzed very slender columns without appropriate additional considerations and modifications. In the case of such columns the yield drift is dominated by the flexural mode (it is practically proportional to the height of the column) and the ultimate drift under cyclic loading conditions is only slightly dependent on the shear span (indicating that the ratio of the equivalent length of the plastic hinge to the height of the column decreases with the increasing shear span). An appropriately modified lumped plasticity model incorporating in-cycle and repeated-cycle strength deterioration was chosen for future use in performance-based design and seismic risk studies.

Earthquake Likelihood Model Testing

The Regional Earthquake Likelihood Models (RELM) project aims to produce and evaluate alternate models of earthquake potential (probability per unit volume, magnitude, and time) for California. Based on differing assumptions, these models are produced to test the validity of their assumptions and to explore which models should be incorporated in seismic hazard and risk evaluation. Tests based on physical and geological criteria are useful but we focus on statistical methods using future earthquake catalog data only. We envision two evaluations: a test of consistency with observed data and a comparison of all pairs of models for relative consistency. Both tests are based on the likelihood method, and both are fully prospective ( i.e. , the models are not adjusted to fit the test data). To be tested, each model must assign a probability to any possible event within a specified region of space, time, and magnitude. For our tests the models must use a common format: earthquake rates in specified “bins” with location, magnitude, time, and focal mechanism limits. Seismology cannot yet deterministically predict individual earthquakes; however, it should seek the best possible models for forecasting earthquake occurrence. This paper describes the statistical rules of an experiment to examine and test earthquake forecasts. The primary purposes of the tests described below are to evaluate physical models for earthquakes, assure that source models used in seismic hazard and risk studies are consistent with earthquake data, and provide quantitative measures by which models can be assigned weights in a consensus model or be judged as suitable for particular regions. In this paper we develop a statistical method for testing earthquake likelihood models. A companion paper (Schorlemmer and Gerstenberger 2007, this issue) discusses the actual implementation of these tests in the framework of the RELM initiative. Statistical testing of hypotheses is a common …

Comparative Seismic Risk Studies for German Earthquake Regions on the Basis of the European Macroseismic Scale EMS-98

Within the framework of recent research projects, basic tools for GIS-based seismic risk assessment technologies were developed and applied to the building stock and regional particularities of German earthquake regions. Two study areas are investigated, being comparable by the level of seismic hazard and the hazard-consistent scenario events (related to mean return periods of 475, 2475 and 10000 years). Significant differences exist with respect to the number of inhabitants, the grade and extent of urbanisation, the quality and quantity of building inventory: the case study of Schmolln in Eastern Thuringia seems to be representative for the majority of smaller towns in Germany, the case study of Cologne (Koln) stands for larger cities. Due to the similarities of hazard and scenario intensities, the considerable differences do not only require proper decisions concerning the appropriate methods and acceptable efforts, they enable conclusions about future research strategies and needs for disaster reduction management. Not least important, results can sharpen the focus of public interest. Seismic risk maps are prepared for different scenario intensities recognising the scatter and uncertainties of site-dependent ground motion and also of the applied vulnerability functions. The paper illustrates the impact of model assumptions and the step-wise refinements of input variables like site conditions, building stock or vulnerability functions on the distribution of expected building damage within the study areas. Furthermore, and in contrast to common research strategies, results support the conclusion that in the case of stronger earthquakes the damage will be of higher concentration within smaller cities like Schmolln due to the site-amplification potential and/or the increased vulnerability of the building stock. The extent of damage will be pronounced by the large number of masonry buildings for which lower vulnerability classes have to be assigned. Due to the effect of deep sedimentary layers and the composition of building types, the urban centre of Cologne will be less affected by an earthquake of comparable intensity.

Conservation of a slender historical Mamluk-style minaret by passive control techniques

During the Egypt/Dahshur 1992 earthquake, a large number of historical Islamic minarets, especially those built during the Mamluk era, were significantly damaged. The level of damage in Mamluk-style minarets was assigned to their massive size, and their irregular distribution of mass and stiffness along their heights. In this paper, the seismic vulnerability of a representative Mamluk-style minaret, namely Manjaq Al-Yusufi (1349 A.D.) is investigated and some seismic protection techniques are proposed and evaluated. Geometrical, material, and geotechnical data were determined at the site. A realistic three-dimensional finite element model of the minaret that reflects those properties was constructed. Ambient vibration tests were then performed on the minaret, and its modal parameters such as fundamental periods and mode shapes were obtained. The ambient vibration test results were then used to update the finite element model. The seismic hazard at the minaret location was evaluated, and a seismic risk study of the minaret was performed with the conclusion that the minarets will be highly vulnerable during moderate earthquakes. A seismic protection technique that includes the use of high damping rubber bearings HDRB and vertical steel anchoring bars is proposed and evaluated. The proposed technique was found to efficiently reduce the seismic risk of the minaret under investigation. Copyright © 2004 John Wiley & Sons, Ltd.

An evolutionary ground motion model for earthquake analysis of structures in zones with little history

Time history methods to perform structural dynamic analysis for vulnerability, seismic risk and structural performance studies are frequent in all kinds of projects. To apply these methods it is necessary to have earthquake acceleration records consistent with the seismic characteristics of the zone where the structure or facilities will be constructed. In regions where seismic activity is important but recorded history is scarce, the simulation of acceleration records becomes necessary.In the present work, a methodology to simulate artificial acceleration records is presented. This methodology is based on the theory of non-stationary random processes with evolutive power spectral density function. The random process model proposed uses the definition of the Boore power spectral density function, in order to take into account the seismic mechanism of the zone. The zone of Mendoza, in the province of Cuyo in Argentina close to the border with Chile, was selected to make applications of the theory. This zone was selected because it has important seismic activity but the information about this activity is scarce. To evaluate the performance of the method some response and seismic variables such as response spectra, Arias evolutionary intensity, and power spectra were computed. The results were compared with actual earthquake data obtained in the region.

Recent Advances in Prediction and Processing of Strong Ground Motions

We present an overview of our recent results on utilizing small earthquakes in the earthquake engineering practice. Site-specific ground motion time-histories of large earthquakes can be successfully simulated using recordings of small earthquakes which are often referred to as 'empirical Green's functions' in seismology. Another important practical problem is whether and how these observations can be used in seismic risk studies which are based on empirical attenuation relations for ground motion parameters. We study a possibility of extrapolating attenuation relations for small earthquakes, to larger magnitudes using the data from the Garner Valley downhole array in Southern California. Finally we introduce efficient ground motion processing techniques in frequency- and time-domains and apply them to site response estimation.

Proterozoic Structure, Cambrian Rifting, and Younger Faulting as Revealed by a Regional Seismic Reflection Network in the Southern Illinois Basin

Four high-quality seismic reflection profiles through the southern Illinois Basin, totaling 245 km in length, provide an excellent regional subsurface stratigraphic and structural framework for evaluation of seismic risk, hydrocarbon occurrence, and other regional geologic studies. These data provide extensive subsurface information on the geometry of the intersection of the Cambrian Reelfoot and Rough Creek rifts, on extensive Proterozoic reflection sequences, and on structures (including the Fluorspar Area Fault Complex and Hicks Dome) that underlie a transitional area between the well-defined New Madrid seismic zone (to the southwest) and a more diffuse area of seismicity in the southern Illinois Basin. Our principal interpretations from these data are listed here in order of geologic age, from oldest to youngest: 1. Prominent Proterozoic layering, possibly equivalent to Proterozoic (∼1 Ga) Middle Run Formation clastic strata and underlying (1.3–1.5 Ga) volcanic rocks of the East Continent rift basin, has been strongly deformed, probably as part of the Grenville foreland fold and thrust belt. 2. A well-defined angular unconformity is seen in many places between Proterozoic and Cambrian strata; a post-Grenville Proterozoic sequence is also apparent locally, directly beneath the base of the Cambrian. 3. We infer a major reversal in Cambrian rift polarity (accommodation zone) in the Rough Creek Graben in western Kentucky. 4. Seismic facies analysis suggests the presence of basin-floor fan complexes at and near the base of the Cambrian interval and within parts of a Proterozoic post-Grenville sequence in several parts of the Rough Creek Graben. 5. There is an abrupt pinchout of the Mount Simon Sandstone against crystalline basement beneath the Dale Dome (near the Texaco no. 1 Cuppy well, Hamilton County) in southeastern Illinois, and a more gradual Mount Simon pinchout to the southeast. 6. Where crossed by the seismic reflection line in southeast Illinois, some faults in the Wabash Valley Fault System produce discrete offset in Ordovician and younger strata only; one of the Wabash Valley faults cuts the top of the Precambrian on this seismic profile. 7. The data show clear evidence of late Paleozoic reverse faulting along both boundaries of the Rough Creek Graben in western Kentucky, although significant unreactivated Cambrian rift-bounding faults are also preserved. 8. Chaotic reflection patterns in the lower and middle Paleozoic strata near Hicks Dome, southern Illinois, are related to a combination of intrusive brecciation, intense faulting, and alteration of carbonate strata by acidic mineralizing fluids, all of which occurred in the Permian. 9. Late Paleozoic(?) reverse faulting is interpreted on one flank of the Rock Creek Graben, southern Illinois. 10. Permian and Mesozoic(?) extensional faulting is clearly imaged in the Fluorspar Area Fault Complex; neotectonic studies suggest that these structures were reactivated in the Quaternary.

Damage Scenarios Simulation for Seismic Risk Assessment in Urban Zones

A methodology for simulating seismic damage of unreinforced masonry buildings for seismic risk assessment of urban areas is presented in this paper. The methodology is based on the Italian vulnerability index and on the results of a post-earthquake damage survey study whose main result was an observed vulnerability function. The Monte Carlo method was then used to simulate damage probability matrices, fragility curves and vulnerability functions, all of which are the basis of a seismic risk study. The simulation process required the generation of thousands of hypothetical buildings, the analysis of their seismic behaviour and probabilistic studies of the computed results. As an example, probable damage scenarios were developed for an urban zone of Barcelona.

Gross design and construction errors, and seismic risk studies

The seismic risk estimates and seismic margin assessment for nuclear power plants should consider the potential effects of design and construction errors. These errors generally modify the component responses and fragilities. The concern with design and construction errors is that they may simultaneously affect a large number of systems and structures and negate the possible benefits of redundancy. A methodology for treating the effects of gross errors in seismic PRA and seismic margin studies consist of enumeration and classification of errors, sensitivity studies to identify significant errors, collection of data on errors and incorporation into the margin and risk estimation.

The connection of geodynamics with seismicity patterns

When a study is to be made of seismic risks, the present-day geodynamic conditions are of fundamental importance: Earthquakes do not happen by themselves, they do have a cause. The cause of earthquakes is that the tectonic stresses exceed a critical limit. The build-up of these stresses is conditioned by the geodynamic processes occurring in the region in question. A knowledge of the geodynamics characteristic of a region is therefore fundamental for seismic risk studies. The general methodology for making such a geodynamic study is based on the entire set of manifestations of the plate-tectonic conditions of that region: these include the mechanism of earthquakes, the stresses observed in mines, the orientation of surface joints and even the direction of river valleys. Examples of geodynamic studies and their bearing on seismic risks are shown from various areas of the world, notably from China, India, and Colombia.

On the macroseismic magnitudes of the largest Italian earthquakes

The macroseismic magnitudes M T of the largest Italian earthquakes ( I 0 ⩾ VIII, MCS) have been computed by using the intensity magnitude relationships recently assessed by the authors (1986) for the Italian region. The Progetto Finalizzato Geodinamica (PFG) catalog of the Italian earthquakes, covering the period 1000–1980 (Postpischl, 1985) is the source data base and is reproduced in the Appendix: here the estimated values of M T are given side by side with the catalog macroseismic magnitudes M K i.e. the magnitudes computed according to the Karnik laws (Karnik, 1969). The one-sigma errors Δ M T are also given for each earthquake. The basic aim of the paper is to provide a handy and useful tool to researchers involved in seismicity and seismic-risk studies on Italian territory.

Cartographie des risques—Methodologie ce dont a besoin l'industrie-des assurances

Nowadays, the significance of geological hazards is constantly increasing, for the whole economy and for the insurance industry in particular. The main reasons for this are the growth of the world population and of economic production and the associated concentration of population and values in highly industrialized areas, as well as the development of highly sensitive technologies and their application in ever more exposed regions. The demands made of geological hazard mapping by the insurance industry differ from those made by, for instance, a structural designer. This is proved in the case of earthquake. The need for a probabilistic approach is common to both disciplines, the difference lying in the choice of the risk parameter. For the structural designer, ground acceleration or velocity is the most suitable parameter for calculating the seismic load acting on a building. For the insurance underwriter intensity is preferable. The main reason is that loss statistics which form the basic input for calculating the earthquake premium nearly always use intensity as risk parameter. Most seismic risk studies indicate recurrence periods for different levels of ground acceleration. A suitable relationship may be established between the risk parameters intensity and acceleration. By introducing a relationship of this type, the use of historical data is made possible in regions of well documented historical seismicity. The approach described above has been applied to compile a world map of the seismic risk and other natural hazards. The risk has been defined in terms of the Mercalli intensity to be expected once in 50 years for average subsoil conditions.

Stochastic Models with Memory for Seismic Risk Evaluation

Most seismic risk studies assume the occurrences of large earthquakes follow a memoryless Poisson Process. Yet, current scientific knowledge describes earthquake occurrences as a memory process of gradual accumulation and sudden release of energy. After reviewing some suggested models for earthquake occurrence, two stochastic models with memory, the Linearly Increasing Hazard Rate (LIHR) model and a continuous time Markov chain model, are offered as simpler alternatives. Using earthquake occurrence data from Lima, Peru, the LIHR model is tested against the Poisson and found to provide a significantly better fit. Some implications of the use of memory processes for insurance and reinsurance problems are explored.

Estimating the seismicity from geological structure for seismic risk studies : Anderson, J G Bull Seismol Soc Am, V69, N1, Feb 1979, P135–158

Estimating the seismicity from geological structure for seismic risk studies : Anderson, J G Bull Seismol Soc Am, V69, N1, Feb 1979, P135–158

Estimating the seismicity from geological structure for seismic-risk studies

abstract Starting with geological data, this paper estimates the seismicity for applications in seismic risk studies. The rate at which seismic moment is released can be estimated on a fault when the slip rate is known. It can also be estimated in a region of crustal convergence (without subduction) or divergence when the rate at which opposite sides of the zone are converging or the regional strain rate is known. Then, provided all of the deformation is released seismically, by assuming the relative frequency of different sizes of earthquakes, the absolute frequency of events can be obtained. The procedure is used to estimate seismicity in southern California. A review of geological literature has provided preliminary estimates of slip rates on many important faults. The estimates of the seismicity resulting from these slip rates are consistent with historical records of earthquake occurrences for southern California taken as a whole. For smaller regions or individual faults in southern California, the seismicity estimated from slip rates may differ from historical rates of seismicity by a factor of two or more. In the western basin and range region, the historical seismicity is also consistent with an estimate for the strain rate. Because of this agreement in larger regions, where many faults are involved, it is inferred that the geological data is also useful for studies of smaller regions, even though on this scale the model cannot be tested because of the too short historical record of earthquake occurrences.