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Major Earthquakes (major + earthquake)
Selected AbstractsUrban earthquake hazard: perceived seismic risk and preparedness in Dhaka City, BangladeshDISASTERS, Issue 2 2010Bimal Kanti Paul Bangladesh is vulnerable to seismic events. Experts suspect that if an earthquake with a 7.0 magnitude occurred in large cities of Bangladesh, there would be a major human tragedy due to the structural failure of many buildings. The primary objectives of this paper are to examine seismic risk perception among residents of Dhaka City and investigate their levels of earthquake preparedness. A questionnaire survey conducted among 444 residents of the city provided the major source of data for the paper. The survey results suggest that an overwhelming majority of the respondents were not prepared for a major earthquake, which is anticipated to occur in Dhaka. Multivariate analysis of survey data reveals that value of residential unit and respondent educational levels appear as the most significant determinants of preparedness status of the respondents. This study recommends increasing earthquake awareness and preparedness among residents of Dhaka City. [source] Post-earthquake bridge repair cost and repair time estimation methodologyEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2010Kevin R. Mackie Abstract While structural engineers have traditionally focused on individual components (bridges, for example) of transportation networks for design, retrofit, and analysis, it has become increasingly apparent that the economic costs to society after extreme earthquake events are caused at least as much from indirect costs as direct costs due to individual structures. This paper describes an improved methodology for developing probabilistic estimates of repair costs and repair times that can be used for evaluating the performance of new bridge design options and existing bridges in preparation for the next major earthquake. The proposed approach in this paper is an improvement on previous bridge loss modeling studies,it is based on the local linearization of the dependence between repair quantities and damage states so that the resulting model follows a linear relationship between damage states and repair points. The methodology uses the concept of performance groups (PGs) that account for damage and repair of individual bridge components and subassemblies. The method is validated using two simple examples that compare the proposed method to simulation and previous methods based on loss models using a power,law relationship between repair quantities and damage. In addition, an illustration of the method is provided for a complete study on the performance of a common five-span overpass bridge structure in California. Intensity-dependent repair cost ratios (RCRs) and repair times are calculated using the proposed approach, as well as plots that show the disaggregation of repair cost by repair quantity and by PG. This provides the decision maker with a higher fidelity of data when evaluating the contribution of different bridge components to the performance of the bridge system, where performance is evaluated in terms of repair costs and repair times rather than traditional engineering quantities such as displacements and stresses. Copyright © 2009 John Wiley & Sons, Ltd. [source] Interseismic Plate coupling and strain partitioning in the Northeastern CaribbeanGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2008D. M. Manaker SUMMARY The northeastern Caribbean provides a natural laboratory to investigate strain partitioning, its causes and its consequences on the stress regime and tectonic evolution of a subduction plate boundary. Here, we use GPS and earthquake slip vector data to produce a present-day kinematic model that accounts for secular block rotation and elastic strain accumulation, with variable interplate coupling, on active faults. We confirm that the oblique convergence between Caribbean and North America in Hispaniola is partitioned between plate boundary parallel motion on the Septentrional and Enriquillo faults in the overriding plate and plate-boundary normal motion at the plate interface on the Northern Hispaniola Fault. To the east, the Caribbean/North America plate motion is accommodated by oblique slip on the faults bounding the Puerto Rico block to the north (Puerto Rico subduction) and to the south (Muertos thrust), with no evidence for partitioning. The spatial correlation between interplate coupling, strain partitioning and the subduction of buoyant oceanic asperities suggests that the latter enhance the transfer of interplate shear stresses to the overriding plate, facilitating strike-slip faulting in the overriding plate. The model slip rate deficit, together with the dates of large historical earthquakes, indicates the potential for a large (Mw7.5 or greater) earthquake on the Septentrional fault in the Dominican Republic. Similarly, the Enriquillo fault in Haiti is currently capable of a Mw7.2 earthquake if the entire elastic strain accumulated since the last major earthquake was released in a single event today. The model results show that the Puerto Rico/Lesser Antilles subduction thrust is only partially coupled, meaning that the plate interface is accumulating elastic strain at rates slower than the total plate motion. This does not preclude the existence of isolated locked patches accumulating elastic strain to be released in future earthquakes, but whose location and geometry are not resolvable with the present data distribution. Slip deficit on faults from this study are used in a companion paper to calculate interseismic stress loading and, together with stress changes due to historical earthquakes, derive the recent stress evolution in the NE Caribbean. [source] Holocene uplift rates and historical rapid sea-level changes at the Gargano promontory, ItalyJOURNAL OF QUATERNARY SCIENCE, Issue 5-6 2002Giuseppe Mastronuzzi Abstract This paper uses a combination of geomorphological and radiometric data from the northern coast of the Gargano promontory (comprising the Fortore River coastal plain and Punta delle Pietre Nere) to reconstruct Holocene uplift rates. The coastal plain consists of a sandy progradational beach sequence that extends seawards from the base of a relict cliff. This cliff probably marks the maximum position reached by the Holocene transgression. Altimetric data compared with the age of beach deposits and the available eustatic sea-level curves indicate an average Holocene uplift rate of 1.5 mm yr,1. A similar uplift rate has been estimated by dating a bioherm constituted of calcareous algae, Vermetids and subordinately by Cladocora caespitosa (L.), which crops out in the locality of Punta delle Pietre Nere. This deposit, which was previously assigned an interglacial age, yielded a mid-Holocene age by means of Th/U and 14C age determinations. Our observations also reveal evidence for coseismic deformation along the northern coast of the Gargano promontory during the last millennium. Vertical displacements of >0.5 m have affected the Punta delle Pietre Nere coastal block, and were preceded by periods of slow coastal subsidence, which increased rapidly shortly before a major earthquake. Copyright © 2002 John Wiley & Sons, Ltd. [source] The effects of 17 August Marmara earthquake on patient admittances to our dermatology departmentJOURNAL OF THE EUROPEAN ACADEMY OF DERMATOLOGY & VENEREOLOGY, Issue 3 2002D Bayramgürler Abstract On 17 August 1999 a devastating earthquake with a magnitude of 7.4 on the Richter scale occurred in Marmara region of Turkey and the epicentre of the earthquake was our city. In this study we aimed to determine the influence of a major earthquake on patient admittance's to the outpatient clinic of our dematology department. All the registrations of the outpatient clinic of our dermatology department in a period of 6 months after the earthquake and the same period last year were revised retrospectively and categorized into 15 subgroups. The first 3 months registrations (earthquake group 1) and the second 3 months registrations (earthquake group 2) after the earthquake were compared with those of the same periods in last year, respectively (control group 1 and control group 2). Also the earthquake group 1 was compared with the earthquake group 2. When the results were evaluated, it was seen that the incidence of infections-infestations was significantly higher in the earthquake group 1 when compared with the control group 1. When the earthquake group 2 and the control group 2 were compared with each other regarding the incidences of the skin diseases, no statistically significant difference was found. The incidences of erythematous-squamous skin diseases, pruritus and neurocutaneous dermatoses and eczemas were significantly higher in the earthquake group 2 when compared with the earthquake group 1. On the other hand, the incidences of infections-infestations and dermatoses due to physical factors were significantly lower in the earthquake group 2 when compared with the earthquake group 1. We think that the alteration in the admittance's to outpatient clinic of our dermatology department in the first 3 months after the earthquake is due to the damaged infrastructures and unhygienic life conditions and in the second 3 months is due to psycho-emotional factors related to earthquake. [source] Seismic vulnerability assessment using regional empirical dataEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2006Ahmet Yakut Abstract This article presents a procedure developed for the seismic performance assessment of low- to mid-rise reinforced concrete buildings in Turkey. The past performance of reinforced concrete buildings during major earthquakes have been compiled and analysed comprehensively using statistical procedures in order to study the empirical correlation between the significant damage inducing parameters and the observed damage. A damage database of nearly 500 representative buildings experiencing the 1999 Kocaeli and Düzce earthquakes have been used and discriminant functions expressing damage score in terms of six damage inducing parameters have been developed. In order to extrapolate the procedure to other regions that are likely to be subjected to major earthquakes a new approach that takes into account different local soil conditions, site-to-source distance and the magnitude of the earthquake has been introduced. The procedure has been applied to a pilot area in Istanbul to estimate expected damage distribution under a credible scenario earthquake. Copyright © 2006 John Wiley & Sons, Ltd. [source] Seismic performance evaluation of steel arch bridges against major earthquakes.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2004Part 1: dynamic analysis approach Abstract In this study the inelastic behavior of steel arch bridges subjected to strong ground motions from major earthquakes is investigated by dynamic analyses of a typical steel arch bridge using a three-dimensional (3D) analytical model, since checking seismic performance against severe earthquakes is not usually performed when designing such kinds of bridge. The bridge considered is an upper-deck steel arch bridge having a reinforced concrete (RC) deck, steel I-section girders and steel arch ribs. The input ground motions are accelerograms which are modified ground motions based on the records from the 1995 Hyogoken-Nanbu earthquake. Both the longitudinal and transverse dynamic characteristics of the bridge are studied by investigation of time-history responses of the main parameters. It is found that seismic responses are small when subjected to the longitudinal excitation, but significantly large under the transverse ground motion due to plasticization formed in some segments such as arch rib ends and side pier bases where axial force levels are very high. Finally, a seismic performance evaluation method based on the response strain index is proposed for such steel bridge structures. Copyright © 2004 John Wiley & Sons, Ltd. [source] Seismic performance evaluation of steel arch bridges against major earthquakes.EARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 14 2004Part 2: simplified verification procedure Abstract The performance-based philosophy has been accepted as a more reasonable design concept for engineering structures. For this purpose, capacity evaluation and demand prediction procedures for civil engineering structures under earthquake excitations are of great significance. This work presents a displacement-based seismic performance verification procedure including capacity and seismic demand predictions for steel arch bridges and investigates its applicability. Pushover analyses is employed as a basis in this method to investigate the structure's behaviors. A failure criterion for steel members accounting for the effect of local buckling is involved and an equivalent single-degree-of-freedom (ESDOF) system with a simplified bilinear hysteretic model formulated using pushover analyses results is introduced to estimate the displacement capacity and maximum demand of steel arch bridges under major earthquakes. To check the accuracy of the proposed method, seismic capacities and demands from multi-degree-of-freedom (MDOF) time-history analyses with Level-II design earthquake record inputs modeling major earthquakes are used as benchmarks for comparison. By a case study, it is clarified that the proposed prediction procedure can give accurate estimations of displacement capacities and demands of the steel arch bridge in the transverse direction, while insufficient for the longitudinal direction, which confirms the conclusion drawn in other structure types about the applicability of pushover analyses. Copyright © 2004 John Wiley & Sons, Ltd. [source] Mechanical deformation model of the western United States instantaneous strain-rate fieldGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2006Fred F. Pollitz SUMMARY We present a relationship between the long-term fault slip rates and instantaneous velocities as measured by Global Positioning System (GPS) or other geodetic measurements over a short time span. The main elements are the secularly increasing forces imposed by the bounding Pacific and Juan de Fuca (JdF) plates on the North American plate, viscoelastic relaxation following selected large earthquakes occurring on faults that are locked during their respective interseismic periods, and steady slip along creeping portions of faults in the context of a thin-plate system. In detail, the physical model allows separate treatments of faults with known geometry and slip history, faults with incomplete characterization (i.e. fault geometry but not necessarily slip history is available), creeping faults, and dislocation sources distributed between the faults. We model the western United States strain-rate field, derived from 746 GPS velocity vectors, in order to test the importance of the relaxation from historic events and characterize the tectonic forces imposed by the bounding Pacific and JdF plates. Relaxation following major earthquakes (M, 8.0) strongly shapes the present strain-rate field over most of the plate boundary zone. Equally important are lateral shear transmitted across the Pacific,North America plate boundary along ,1000 km of the continental shelf, downdip forces distributed along the Cascadia subduction interface, and distributed slip in the lower lithosphere. Post-earthquake relaxation and tectonic forcing, combined with distributed deep slip, constructively interfere near the western margin of the plate boundary zone, producing locally large strain accumulation along the San Andreas fault (SAF) system. However, they destructively interfere further into the plate interior, resulting in smaller and more variable strain accumulation patterns in the eastern part of the plate boundary zone. Much of the right-lateral strain accumulation along the SAF system is systematically underpredicted by models which account only for relaxation from known large earthquakes. This strongly suggests that in addition to viscoelastic-cycle effects, steady deep slip in the lower lithosphere is needed to explain the observed strain-rate field. [source] What a difference a year makes: How immediate and anniversary media reports influence judgements about earthquakesASIAN JOURNAL OF SOCIAL PSYCHOLOGY, Issue 3 2002Jodie Cowan Research suggests that the content of newspaper and television reports about natural disasters, such as earthquakes, affects people's fatalistic judgements about these disasters. The present paper contains two studies, Study 1 and Study 2. Study 1 examined features in newspaper reports written at two time points following two major earthquakes: immediately after the earthquakes and a year following the earthquakes. These reports showed several features about the earthquakes: in reports immediately after the earthquakes, the reports were concerned about earthquake agency and general damage; and in reports written a year following the earthquakes, the reports portrayed specific damage and lessons. Study 2 examined the influence of these features on students' (n = 160) estimates of the extent of damage, attributions for damage and judgements of the preventability of the damage. With excerpts presenting specific damage and lessons, participants gave lower estimates of damage, judged damage to be more preventable and attributed the damage more to building design than with earthquake agency and general damage descriptions of the same earthquakes. These findings have clear implications for the way the media and civic education programs present information on earthquakes and other disasters. [source] The Effects of the 1999 Turkish Earthquake on Young Children: Analyzing Traumatized Children's Completion of Short StoriesCHILD DEVELOPMENT, Issue 4 2010Elif Celebi Oncu The purpose of this exploratory study was to determine whether projective techniques could identify long-term consequences among children stemming from exposure to a traumatic event. The first group of children (n = 53; 26 female, 27 male) experienced 2 major earthquakes at age 7, 3 months apart, in Turkey, while a similarly matched control group (n = 50; 25 female, 25 male) did not. Both groups of children (current age: 9) completed a series of short stories related to disastrous events. Results indicated that the traumatized group evinced a range of trauma-related symptoms 2 years after experiencing the earthquakes. [source] | |||||||||||||