Seismic hazard

Failure frequencies of structures, equipment, and piping are related to their acceleration which is related to the ground-motion of the plant s foundation (e.g., the peak ground acceleration). For PSA, it is useful to present the seismic hazard at the site as a family of hazard curves with different nonexceedence-probability levels (Figure 5.1-3). By selecting various values of the peak ground acceleration, the acceleration and forces on the plant components may be obtained as described in the following. 

The external events PSA was based on standard methods used for commercial reactor PSAs, Fire risk was estimated from commercial nuclear power plant data combined with industrial fire information. The seismic hazard was evaluated using a combination of the EPRI and LLNL ( UREG/CR-.3250) databases. Wind hazards were analyzed by EQE, Inc., using NRC-based nicihodulogy. 

LLNL was contracted to use the results of the Seismic Hazard Characterization Project (SHCP). (NUREG/CR-5250) to calculate the seismic hazard at the SRS using methods similar to the Seismic Owners Group-Electric Power Research Institute (SOG/EPRI) and LLNL the (wo seismic hazard estimates for the SRS are different. The SHCP (Savy, 1988) seismic hazani results are typically within a factor of 5. Results of the seismic analysis are given in Table 11.3-6... 

Bernreuter, D. L. et al., Seismic Hazard Characterization of 69 Nuclear Plant Sites East of the Rocky Mountains, Methodology, Input Data, and Commparisons with Previous Results, Vol 1-8, January 1989,... 

Savy, J. B., 1980, Seismic Hazard Analysis of the Savannah River Site, UCID-21596, November. 

We conclude that a multiparameter approach including parameters related to different seismicity patterns is promising for the improvement of seismic hazard assessment. 

Kiyashchenko, D., Smirnova, N., Troyan, V., Saenger, E., Vallianatos, F. 2004, Seismic hazard precursory evolution fractal and multifractal aspects. Physics and Chemistry of the Earth 29(4-9) 367-378. 

The local site effects play an important role in the evaluation of seismic hazard. The proper evaluation of the local site effects will help in evaluating the amplification factors for different locations. This article deals with the evaluation of peak ground acceleration and response spectra based on the local site effects for the study area. The seismic hazard analysis was done based on a probabilistic logic tree approach and the peak horizontal acceleration (PHA) values at the bed rock level were evaluated. Different methods of site classification have been reviewed in the present work. The surface level peak ground acceleration (PGA) values were evaluatedfor the entire study area for four different site classes based on NEHRP site classification. The uniform hazard response spectrum (UHRS) has been developed for the city of Bangalore and the details are presented in this work. 

If the seismic source is spread over an area, then it may not be appropriate to model it as a linear source. To overcome this limitation areal sources, sources which are spread over an area, were also considered in this study. The smoothed historic seismicity approach suggested by Frankel (1995) was adopted for smoothing the areal seismic sources. For the evaluation of seismic hazard, spatially smoothed areal sources, identified based on earthquakes of magnitude 4 and above were used. 

SEISMIC HAZARD EVALUATION BASED ON PROBABILISTIC LOGIC TREE APPROACH... 

There are two different methods for quantifying the seismic hazard - based on deterministic approach and probabilistic approach. The deterministic seismic hazard analysis (DSHA) does not consider the uncertainties involved in the earthquake occm-rence process like the recurrence rate, magnitude uncertainty, attenuation characteristics of seismic waves etc. and gives the worst scenario of ground acceleration. Probabilistic seismic hazard analysis (PSHA) incorporates the uncertainties involved in the earthquake occurrence process. Since the uncertainty in earthquake occurrence is fully accounted in this method, this method is being widely followed for the evaluation of seismic hazard. The PSHA method adopted in this study... 

Bommer, J., Scherbaum, F., Bungum, H., Cotton, F., Sabetta, F., Abrahamson, N. A. (2005). On the use of logic trees for ground-motion prediction equations in seismic hazard analysis. Bulletin ofthe Seismological Society of America, 95, 377-389. doi 10.1785/0120040073... 

Frankel, A. (1995). Mapping seismic hazard in the Central Eastern United States. Seismological Research Letters, 66(4), 8-21. 

Raghu Kanth, S. T. G., Iyengar, R. N. (2006). Seismic hazard estimation for Mumbai city. Current Science, 97(11), 1486-1494. 

Seeber, L., Armbruster, J. G., Jacob, K. H. (1999). Probabilistic Assessment of Seismic Hazard for Maharashtra, Govt, of Maharashtra. Unpublished Report. 

Steidl, J. H. (2000). Site response in southern California for probabilistic seismic hazard analysis. 

Stepp, J. C., Wong, I., Whitney, J., Quittemeyer, R., Abrahamson, N., Toro, G. (2001). Yucca Mountain PSHA Project Members, Probabilistic seismic hazard analyses for ground motions and fault displacements at Yucca Mountain, Nevada. Earthquake Spectra, 17, 113-151. doi 10.1193/l.1586169... 

Seismic hazard analysis which involves collection of seismicity and seismotectonic of the region, selection of predictive relationship to arrive at controlling earthquake... 

In the past 20 to 30 years the use of probabilistic concepts has allowed uncertainties in the size, location and rate of recurrence of earthquakes and in the variation of ground motion characteristics with earthquake size and location to be explicitly considered in the evaluation of seismic hazards. Probabilistic seismic hazard analysis (PSHA) provides aframe-work in which these uncertainties can be identified, quantified, and combined in a rational mannerto provide amore complete picture of seismic hazard. The proper performance of a PSHA requires careful attention to the problems of source characterization and ground motion parameter prediction and to the mechanics of the probability computations. 

Deterministic Seismic Hazard Analysis (DSHA) analysis is simple and more prevalent methods of hazard analysis in geotechnical earthquake engineering. DSHA involves the development of a particular seismic scenario upon which a ground motion hazard evaluation is based. The scenario consists of the postulated occurrence of an earthquake of a specified size occurring at a specified location. DSHA is more logical, more transparent, and more appropriate for requirements in engineering design. DSHA... 

Deterministic seismic hazard analysis involves the following steps (Reiter, 1990) which are discussed in detail in the succeeding sections. 

A Site specific evaluation of design ground motion parameters for a seismically vulnerable site located 12 km from Ahmedabad (Gujarat) was carried out involving both seismic hazard analysis and ground response analysis. The seismic hazard... 

Boominathan, A., Dodagoudar, G. R., Suganthi, A., UmaMaheshwari, R. (2008). Seismic hazard assessment of Chennai city considering local site effects. JournalofEarthSystem Science, 117(S2), 853-863. doi 10.1007/S12040-008-0072-4... 

Cramer, C.H., Wheeler, R.L. (2001). The 2001 Gujarat, India earthquake and seismic hazard in central and Eastern North America. Abstract in Seismological Research Letters, 72, 396. 

Frankel, A., Mueller, C., Bamhard, T, Perkins, D., Leyendecker, E. V, Dickman, N. (1996). National seismic hazard maps documentation June 1996. U.S. Geological Survey Open-file Report, 96-532. 

Kijko, A., Graham, G. (1998). Parametric-historic procedure forprobabilistic seismic hazard analysis. Part I Estimation of maximum regional magnitude Mmax. Pure and Applied Geophysics, 152,413-442. doi 10.1007/s000240050161... 

Kramer, S. L, Stewart, J. P. (2004). Geotechnical aspects of seismic hazards In Earthquake Engineering from Engineering Seismology to Performance Based Engineering. CRC press. 

Sitharam, T.G., Anbazhagan, P. (2007). Seismic hazard analysis for Bangalore region. Journal of natural hazards, 40, 261-278. 

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