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1.
A reliable and homogenized earthquake catalogue is essential for seismic hazard assessment in any area. This article describes the compilation and processing of an updated earthquake catalogue for Pakistan. The earthquake catalogue compiled in this study for the region (quadrangle bounded by the geographical limits 40–83° N and 20–40° E) includes 36,563 earthquake events, which are reported as 4.0–8.3 moment magnitude (MW) and span from 25 AD to 2016. Relationships are developed between the moment magnitude and body, and surface wave magnitude scales to unify the catalogue in terms of magnitude MW. The catalogue includes earthquakes from Pakistan and neighbouring countries to minimize the effects of geopolitical boundaries in seismic hazard assessment studies. Earthquakes reported by local and international agencies as well as individual catalogues are included. The proposed catalogue is further used to obtain magnitude of completeness after removal of dependent events by using four different algorithms. Finally, seismicity parameters of the seismic sources are reported, and recommendations are made for seismic hazard assessment studies in Pakistan.  相似文献   

2.
Earthquakes trigger other earthquakes and build up clusters in space and time that in turn create a bias in seismic catalogues. Therefore, declustering is considered as a prerequisite in seismic studies, particularly for probabilistic seismic hazard analysis, not only to eliminate the bias but also to decouple mainshocks and triggered events. However, a declustering process is not a straightforward task due to the complex nature of earthquake phenomena. There exist several declustering methods that mostly employ subjective rules to distinguish between background seismicity and offsprings. Eventually, the final declustered catalogues usually deviate significantly according to the employed method. This issue is raising some concerns, such as how to select the most suitable declustering algorithm, or to assess how this selection affects seismic hazard assessment. In consequence, the main goal of this paper is to quantify the sensitivity of seismic hazard assessments to different declustering techniques. Accordingly, the recently compiled Turkish earthquake catalogue was declustered by making use of three declustering algorithms. A total of six declustered catalogues, two catalogues per method, one by implementing the default input parameters, and one by altering the free input parameters of the employed methods, were produced. The clusters of selected earthquakes were studied in terms of the spatial–temporal distribution of earthquake sequences. A sensitivity analysis was conducted through the major steps of seismic hazard assessment for Istanbul metropolitan city. The seismicity of Istanbul and surroundings was modeled on the basis of four areal source zones. Comparative studies showed that, while the selected declustering algorithm did not significantly affect the completeness periods of moderate to large size earthquakes, it considerably altered those of small magnitude events (e.g. Mw 4.3–5.2) and consequently the recurrence parameters of the source zones. Depending on the declustering algorithm and input parameters, the activity rate was observed to vary up to a factor of two. The differences in the declustered catalogues obtained from different declustering approaches resulted in considerable variations in seismic hazard estimations. The hazard maps at return periods of 475 and 2475 years indicated that peak ground acceleration values may vary up to 20% at some locations. Moreover, the differences in 5% damped elastic spectral accelerations at T = 0.2 for the return periods of 475 and 2475 years are about 18 and 12%, respectively, on the southern shores of Istanbul where the highest hazard levels are observed.  相似文献   

3.
《Journal of Geodynamics》2010,49(3-5):269-278
The project “Seismic Hazard Assessment for Almaty” has a main objective to improve existing seismic hazard maps for the region of northern Tien Shan and especially for the surroundings of Almaty and to generate a new geodynamic model of the region.In the first step a composite seismic catalogue for the northern Tien Shan region was created, which contains about 20,000 events and is representative for strong earthquakes for the period back to the year 500. For the period of instrumental observation 1911–2006 the catalogue contains data for earthquakes with a body wave magnitude larger than 4. For smaller events with magnitudes up to 2.2 the data are only available since 1980. The composite catalogue was created on the basis of several catalogues from the United States Geologic Survey (USGS), local catalogues from the Kazakh National Data Centre (KNDC) and the USSR earthquake catalogue. Due to the different magnitudes used in several catalogues a magnitude conversion was necessary.Event density maps were created to rate the seismicity in the region and to identify seismic sources. Subsurface fault geometries were constructed using tectonic model which uses fault parallel material flow and is constrained by GPS data. The fault geometry should improve the estimation of the expected seismic sources from seismic density maps.First analysis of the earthquake catalogue and the density maps has shown that nearly all large events are related to fault systems. Annual seismicity distribution maps suggest different processes as the cause for the seismic events. Apart from tectonics, also fluids play a major part in triggering of the earthquakes.Beneath the Issyk-Kul basin the absence of strong seismic activity suggests aseismic sliding at the flat ramp in a ductile crust part and low deformation within the stable Issyk-Kul micro-continent which underthrust the northern ranges of Tien Shan. First results suggest a new partition of the region in tectonic units, whose bounding faults are responsible for most of the seismic activity.  相似文献   

4.
Artificial earthquake catalogue simulation is one of the ways to effectively improve the incompleteness of the existing earthquake catalogue,the scarcity of large earthquake records and the improvement of seismological research.Based on the Poisson distribution model of seismic activity and the Gutenberg-Richter magnitude-frequency relationship, the Monte Carlo method which can describe the characteristics of the stochastic nature and the physical experiment process is used.This paper simulates the future seismic catalogues of the Fenhe-Weihe seismic belt of different durations and conducts statistical tests on them. The analysis shows that the simulation catalogue meets the set seismic activity parameters and meets the Poisson distribution hypothesis,which can obtain a better simulated earthquake catalogues that meets the seismic activity characteristics.According to the simulated earthquake catalogues,future earthquake trends in this region are analyzed to provide reference for seismic hazard analysis.  相似文献   

5.
This work focuses on the evaluation of the seismic hazard for Romania using earthquake catalogues generated by a Monte Carlo approach. The seismicity of Romania can be attributed to the Vrancea intermediate-depth seismic source and to 13 other crustal seismic sources. The recurrence times of large magnitude seismic events (both crustal and subcrustal), as well as the moment release rates are computed using simulated earthquake catalogues. The results show that the largest contribution to the overall moment release for the crustal seismic sources is from the seismic regions in Bulgaria, while the seismic regions in Romania contribute less than 5% of the overall moment release. In addition, the computations show that the moment release rate for the Vrancea subcrustal seismic source is about ten times larger than that of all the crustal seismic sources. Finally, the Monte Carlo approach is used to evaluate the seismic hazard for 20 cities in Romania with populations larger than 100,000 inhabitants. The results show some differences between the seismic hazard values obtained through Monte-Carlo simulation and those in the Romanian seismic design code P100-1/2013, notably for cities situated in the western part of Romania that are influenced by local crustal seismic sources.  相似文献   

6.
Located on the Alpine-Himalayan earthquake belt, Iran is one of the seismically active regions of the world. Northern Iran, south of Caspian Basin, a hazardous subduction zone, is a densely populated and developing area of the country. Historical and instrumental documented seismicity indicates the occurrence of severe earthquakes leading to many deaths and large losses in the region. With growth of seismological and tectonic data, updated seismic hazard assessment is a worthwhile issue in emergency management programs and long-term developing plans in urban and rural areas of this region. In the present study, being armed with up-to-date information required for seismic hazard assessment including geological data and active tectonic setting for thorough investigation of the active and potential seismogenic sources, and historical and instrumental events for compiling the earthquake catalogue, probabilistic seismic hazard assessment is carried out for the region using three recent ground motion prediction equations. The logic tree method is utilized to capture epistemic uncertainty of the seismic hazard assessment in delineation of the seismic sources and selection of attenuation relations. The results are compared to a recent practice in code-prescribed seismic hazard of the region and are discussed in detail to explore their variation in each branch of logic tree approach. Also, seismic hazard maps of peak ground acceleration in rock site for 475- and 2,475-year return periods are provided for the region.  相似文献   

7.
For faster and more robust ray tracing in 1-D velocity models and also due to the lack of reliable 3-D models, most seismological centers use 1-D models for routine earthquake locations. In this study, as solution to the coupled hypocenter-velocity problem, we compute a regional P-wave velocity model for southern Iran that can be used for routine earthquake location and also a reference initial model for 3-D seismic tomography. The inversion process was based on travel time data from local earthquakes paired reports obtained by merging the catalogues of Iranian Seismic Center (IRSC, 6422 events) and by the Broadband Iranian National Seismic Network (BIN, 4333 events) for southern Iran in the period 2006 through July 2017. After cleaning the data set from large individual reading errors and by identifying event reports from both networks belonging to same earthquake (a process called event pairing), we obtained a data set of 1115 well-locatable events with a total number of 24,606 P-wave observations. This data set was used to calculate a regional minimum 1-D model for southern Iran as result of an extensive model search by trial-and-error process including several dozens of inversions. Significantly different from previous models, we find a smoothly increasing P-velocity by depth with velocities of 5.8 km/s at shallow and velocities of 6.4 km/s at deepest crustal levels. For well-locatable events, location uncertainties are estimated in the order of ±?3 km for epicenter and double this uncertainty for hypocentral depth. The use of the minimum 1-D model with appropriate station delays in routine hypocenter location processing will yield a high-quality seismic catalogue with consistent uncertainty estimates across the region and it will also allow detection of outlier observations. Based on the two catalogues by IRSC and BIN and using the minimum 1-D model and station delays for all stations in the region, we established a new combined earthquake catalogue for southern Iran. While the general distribution of the seismicity corresponds well with that of the two individual catalogues by IRSC and BIN, the new catalogue significantly enhances the correlation of seismicity with the regional fault systems within and between the major crustal blocks that as an assembly build this continental region. Furthermore, the unified seismic catalogue and the minimum 1-D model resulting from this study provide important ingredients for seismic hazard studies.  相似文献   

8.
A new seismic hazard model for Cairo, the capital city of Egypt is developed herein based on comprehensive consideration of uncertainties in various components of the probabilistic seismic hazard analysis. The proposed seismic hazard model is developed from an updated catalogue of historical and instrumental seismicity, geodetic strain rates derived from GPS-based velocity-field of the crust, and the geologic slip rates of active faults. The seismic source model consists of area sources and active faults characterised to forecast the seismic productivity in the region. Ground motion prediction models are selected to describe the expected ground motion at the sites of interest. The model accounts for inherent epistemic uncertainties of statistical earthquake recurrence; maximum magnitude; ground motion prediction models, and their propagation toward the obtained results. The proposed model is applied to a site-specific hazard analysis for Kottamiya, Rehab City and Zahraa-Madinat-Nasr (hereinafter referred to as Zahraa) to the East of Cairo (Egypt). The site-specific analysis accounts for the site response, through the parameterization of the sites in terms of average 30-m shear-wave velocity (Vs30). The present seismic hazard model can be considered as a reference model for earthquake risk mitigation and proper resilience planning.  相似文献   

9.
山西地区不同时段地震目录最小完整性震级研究   总被引：2，自引：0，他引：2  
王霞  宋美琴  李丽  罗勇 《地震》2014,34(2):82-88
对地震目录的最小完整性震级MC的科学评估, 是进行地震活动性和地震危险性分析的重要基础, 而最小完整性震级MC又是表征台网监测能力的关键参数。 本文据山西地震观测台网建设时间的阶段性差异, 将其分为4个时段, 以1970—2012年山西地区地震目录为基础资料, 利用震级-序号法、 最大曲率法(MAXC)、 90%和95%的拟合度GFT法, 研究了不同时段山西地区地震目录最小完整性震级MC的时序变化特征。 1970年以来随着山西测震台网的改造, MC逐步降低, 尤其是“十五”数字化台网改造后, 山西ML≥0.9地震基本完整, 表明山西地震监测能力逐步提升。  相似文献   

10.
—A new methodology for probabilistic seismic hazard analysis is described. The approach combines the best features of the "deductive" (Cornell, 1968) and "historic" (Veneziano et al., 1984) procedures. It can be called a "parametric-historic" procedure. The maximum regional magnitude mmax is of paramount importance in this approach and Part I of the authors’ work (Kijko and Graham, 1998) was dedicated to developing efficient statistical procedures that can be used for the evaluation of this parameter. In Part II the approach of a probabilistic seismic hazard assessment at a given site is described. The approach permits the utilization of incomplete earthquake catalogues. It is assumed that a typical catalogue contains two types of information historical macroseismic events that occurred over a period of a few hundred years and recent, instrumental data. The historical part of the catalogue contains only the strongest events, whereas the complete part can be divided into several subcatalogues, each assumed complete above a specified threshold of magnitude. The author’s approach also takes into account uncertainty in the determination of the earthquake magnitude. The technique has been developed specifically for the estimation of seismic hazard at individual sites, without the subjective judgment involved in the definition of seismic source zones, in which specific active faults have not been mapped and identified, and where the causes of seismicity are not well understood. As an example of the application of the new technique, the results of a typical hazard analysis for a hypothetical engineering structure located in the territory of South Africa are presented. It was assumed that the only reliable information in the assessment of the seismic hazard parameters in the vicinity of the selected site comes from a knowledge of past seismicity. The procedure was applied to seismic data that were divided into an incomplete part, containing only the largest events, and two complete parts, containing information obtained from instruments. The simulation experiments described in Part I of our study have shown that the Bayesian estimator K-S-B tends to perform very well, especially in the presence of inevitable deviations from the simple Gutenberg–Richter model. In the light of this fact value &gif1; = 6.66 - 0.44, which was obtained from the K-S-B technique, was regarded as the best choice. At an exceedance probability of 10х per annum, the median value of peak ground acceleration on rock at the site is 0.31g, and at an exceedance probability of 10ц per annum, the median peak ground acceleration at the site is 0.39g. The median value of the maximum possible acceleration at the site is 0.40g, which was calculated from attenuation formulae by assuming the occurrence of the strongest possible earthquake, e.g., with magnitude &gif1; = 6.66 at distance 10 km.  相似文献   

11.
Many catalogues, agency reports and research articles have been published on seismicity of Turkey and its surrounding since 1950s. Given existing magnitude heterogeneity, erroneous information on epicentral location, event date and time, this past published data however is far from fulfilling the required standards. Paucity of a standardized format in the available catalogues have reinforced the need for a refined and updated catalogue for earthquake related hazard and risk studies. During this study, ~37,000 earthquakes and related parametric data were evaluated by utilizing more than 41 published studies and, an integrated database was prepared in order to analyse all parameters acquired from the catalogues and references for each event. Within the scope of this study, the epicentral locations of M ≥ 5.0 events were firstly reappraised based on the updated Active Fault Map of Turkey. An improved catalogue of 12.674 events for the period 1900–2012 was as a result recompiled for the region between 32–45N° and 23–48E° by analyzing in detail accuracy of all seismological parameters available for each event. The events consist of M ≥ 4.0 are reported in several magnitude scales (e.g. moment magnitude, Mw; surface wave magnitude, MS; body-wave magnitude mb; local magnitude ML and duration magnitude Md) whereas the maximum focal depth reaches up to 225-km. In order to provide homogenous data, the improved catalogue is unified in terms of Mw. Fore-and aftershocks were also removed from the catalogue and completeness analyses were performed both separately for various tectonic sources and as a whole for the study region of interest. Thus, the prepared homogenous and declustered catalogue consisting of 6573 events provides the basis for a reliable input to the seismic hazard assessment studies for Turkey and its surrounding areas.  相似文献   

12.
A novel generalized probabilistic formulation is proposed to assess seismicity using earthquake catalogues with uncertain and incomplete data. The seismicity, described by the complete exceedance rate of magnitudes, is estimated starting from a consistent incomplete exceedance rate which is rationally linked to the catalogue data. Complete and incomplete exceedance rates are represented by similar functional forms and they are related by a completeness function, which expresses the probability that an event is included in a data set. Completeness is considered uncertain and it is defined by a suitable, continuous, analytical, magnitude dependent function. The importance of this work lies on its applicability because it can be useful in seismic zones where information about seismic activity is scarce or simply when the catalogue is incomplete in a range of magnitudes that can have a significant influence on the seismic hazard analysis and on the resulting seismic risk assessment. Moreover, it can also be applied in the common case when the catalogue is considered complete above a given magnitude threshold. Numerical examples are presented to illustrate the influence of catalogue incompleteness on the complete exceedance rate estimations. In companion papers, attention is focused on the estimation of completeness probabilities of available catalogues and on parameter estimation of the exceedance rate functions.  相似文献   

13.
The accurate evaluation and appropriate treatment of uncertainties is of primary importance in modern probabilistic seismic hazard assessment (PSHA). One of the objectives of the SIGMA project was to establish a framework to improve knowledge and data on two target regions characterized by low-to-moderate seismic activity. In this paper, for South-Eastern France, we present the final PSHA performed within the SIGMA project. A new earthquake catalogue for France covering instrumental and historical periods was used for the calculation of the magnitude-frequency distributions. The hazard model incorporates area sources, smoothed seismicity and a 3D faults model. A set of recently developed ground motion prediction equations (GMPEs) from global and regional data, evaluated as adequately representing the ground motion characteristics in the region, was used to calculate the hazard. The magnitude-frequency distributions, maximum magnitude, faults slip rate and style-of-faulting are considered as additional source of epistemic uncertainties. The hazard results for generic rock condition (Vs30 = 800 m/s) are displayed for 20 sites in terms of uniform hazard spectra at two return periods (475 years and 10,000 years). The contributions of the epistemic uncertainties in the ground motion characterizations and in the seismic source characterization to the total hazard uncertainties are analyzed. Finally, we compare the results with existing models developed at national scale in the framework of the first generation of models supporting the Eurocode 8 enforcement, (MEDD 2002 and AFPS06) and at the European scale (within the SHARE project), highlighting significant discrepancies at short return periods.  相似文献   

14.
—?Earthquake hazard parameters are estimated by the application of the maximum likelihood method. The technique is based on a procedure which utilizes data of different quality, e.g., those in which the uncertainty in the assessment of the magnitudes is great and those in which the magnitudes are computed with great precision. In other words the data were extracted from both historical (incomplete) and recorded (complete) files. The historical part of the catalogue contains only the strongest events, whereas the complete part can be divided into several sub-catalogues; each one assumed to be complete above a specified magnitude threshold. Uncertainty in the determination of magnitudes has also been taken into account. The method allows us to estimate the earthquake hazard parameters which are the maximum regional magnitude, M max, the activity rate, λ, of the seismic events and the well known value β (b=β?log?e), which is the slope of the magnitude-frequency relationship. All these parameters are of physical significance. The mean return periods, RP, of earthquakes with a certain lower magnitude M?≥?m are also determined. The method is applied in the Island of Crete and the adjacent area, where catastrophic earthquakes are known from the historical era. The earthquake hazard of the whole area is divided in a cellular manner which allow the analysis of the localized hazard parameters and the representation of their regional variation. The seismic hazard analysis, which is expressed by: (a) The annual probability of exceedance of a specified value of magnitude and (b) the return periods (in years) that are expected for given magnitudes, for shallow events is finally performed for shallow events. This hazard analysis is useful for both theoretical and practical reasons and provides a tool for earthquake resistant design in both areas of low and high seismicity.  相似文献   

15.
青海省及邻近区域历史地震目录完整性分析探讨   总被引：3，自引：0，他引：3  
以b值研究为基础,运用多种手段对青海及邻近区域的地震目录的完整性进行了分析研究,大致确定了不同震级下限的完整目录的起始时间,得出如下结果:认为4.7级以上地震的完整起始年为1960年左右,5.0级地震的完整起始年为1950年左右;5.5级以上地震的完整起始年为1925年左右;6级以上地震的完整时段为1917年左右。  相似文献   

16.
The parametric catalogues of historical earthquakes in East Siberia contain large data gaps. Among these is a 15-year period in the late nineteenth century (1886–1901). This period was not covered by any of macroseismic catalogues known; neither acquisition nor systematization of macroseismic data was ever performed for that purpose. However, 15 years is a rather long period in which large seismic events may have occurred. The present paper deals with the previously unknown earthquake that occurred on November 13, 1898. The primary macroseismic data were taken from regional periodicals. On the strength of all the evidence obtained, the earthquake epicenter is localized in Western Transbaikalia, near the western end of the Malkhansky Range; the magnitude is estimated at M?=?5.9. The information about the large earthquake of November 13, 1898 provides filling significant gaps in knowledge for seismicity in Western Transbaikalia and a better understanding of seismic potential of faults therein. The obtained results show that the periods of seismic quiescence in catalogues may be related to insufficient information on seismicity of Eastern Siberia in the historical past rather than to the absence of large earthquakes.  相似文献   

17.
Historical earthquakes noted in the written records of the South China region, including Hong Kong, are not well delineated along identified prominent fault sources. Despite the lack of any definitive, localised trend in the spatial distribution of seismic activity in the region, there does appear to be some major disparity in the seismic activity rates (especially for large magnitude earthquakes) between the near-field and the far-field regions of Hong Kong. Despite this observation, previous studies of the regional seismic activity and seismic ground motion hazard (the latter using a probabilistic seismic hazard assessment, PSHA) have considered very broad source zone regions, in which uniform levels of seismic activity have been assumed. The present paper further scrutinises this broad source zone (BSZ) approach by adopting a novel expanding circular disc (ECD) method to determine the rates of earthquake recurrence. Such a method is intended to counter-check previously developed models by determining earthquake scenario events in terms of magnitude–distance (M–R) pairs or combinations, having defined values of average return period. Unlike the BSZ approach, the ECD method specifically accounts for the supposed variations in the seismic activity rates between events in the near-field and the far-field of Hong Kong.The form of the developed method is particularly suited to the determination of design-level earthquake ground motions for bedrock sites, since it assumes a directionally-independent attenuation model as described in the companion paper. It is found that, whilst the BSZ approach may indicate the overall average levels of hazard that are representative of the South China region as a whole, it does not capture the large disparity in seismic activity rates between near-field and far-field events. This important feature is expected to have a significant impact upon engineering assessments of the seismic safety of structures in Hong Kong and elsewhere in the South China region. For example, it is found that for events with M≥6, the seismic activity rate (normalised by time and area) in the very far-field is around 3.5 times larger than in the near-field and medium-field of Hong Kong. The resulting design M-R combinations, covering a range of return periods from 70 to 2500 years, are limited, for very long return periods and for distant events, by the maximum credible earthquake (MCE) magnitude. Intensive research to determine this seismic hazard parameter is recommended, in order to refine further the results of the ECD analysis, which presently conservatively assumes the MCE to range between M=6 in the near-field of Hong Kong to M=8 in the very far-field, at distances greater than 280 km from Hong Kong.  相似文献   

18.
田建伟  刘哲  任鲁川 《地震》2017,37(1):158-165
选取马尼拉海沟俯冲带作为潜源区, 基于广义帕累托分布, 通过对一定时段内超过某一阈值的震级数据进行拟合, 建立该潜源区地震危险性估计模型, 估计强震重现水平和震级上限, 并对估计结果的不确定性进行了分析, 得到马尼拉海沟俯冲带震级上限为9.0级, 10 a、 50 a、 100 a、 200 a马尼拉海沟俯冲带的震级重现水平期望值分别为7.1级、 7.6级、 7.7级、 7.9级。  相似文献   

19.
This article is devoted to application of a simulation algorithm based on geostatistical methods to compile and update seismotectonic provinces in which Iran has been chosen as a case study. Traditionally, tectonic maps together with seismological data and information (e.g., earthquake catalogues, earthquake mechanism, and microseismic data) have been used to update seismotectonic provinces. In many cases, incomplete earthquake catalogues are one of the important challenges in this procedure. To overcome this problem, a geostatistical simulation algorithm, turning band simulation, TBSIM, was applied to make a synthetic data to improve incomplete earthquake catalogues. Then, the synthetic data was added to the traditional information to study the seismicity homogeneity and classify the areas according to tectonic and seismic properties to update seismotectonic provinces. In this paper, (i) different magnitude types in the studied catalogues have been homogenized to moment magnitude (Mw), and earthquake declustering was then carried out to remove aftershocks and foreshocks; (ii) time normalization method was introduced to decrease the uncertainty in a temporal domain prior to start the simulation procedure; (iii) variography has been carried out in each subregion to study spatial regressions (e.g., west-southwestern area showed a spatial regression from 0.4 to 1.4 decimal degrees; the maximum range identified in the azimuth of 135?±?10); (iv) TBSIM algorithm was then applied to make simulated events which gave rise to make 68,800 synthetic events according to the spatial regression found in several directions; (v) simulated events (i.e., magnitudes) were classified based on their intensity in ArcGIS packages and homogenous seismic zones have been determined. Finally, according to the synthetic data, tectonic features, and actual earthquake catalogues, 17 seismotectonic provinces were introduced in four major classes introduced as very high, high, moderate, and low seismic potential provinces. Seismotectonic properties of very high seismic potential provinces have been also presented.  相似文献   

20.
A project has been implemented in recent years for assessing seismic hazard in the Italian territory on probabilistic bases, to be used as scientific background for the revision of the current seismic zonation. A consolidated approach was considered for the purpose; seismic hazard was estimated in terms of peak ground acceleration and macroseismic intensity. As the computer code employed allows the user to make specific choices on some input data, some rather unorthodox decisions were taken regarding earthquake catalogue completeness, seismicity rates, boundaries of the seismogenic zones, definition of the maximum magnitude, attenuation relation, etc. The overwhelming amount of geological and seismological data for Italy (just consider, for example, that the earthquake catalogue collects events which occurred over the last ten centuries) permits the operator to make different choices, more or less cautiously. It is quite interesting, then, to evaluate the influence of the specific choices on the final hazard results as a comparison to traditional possibilities. The tests performed clearly indicate the critical choices and quantify their contribution. In particular, we consider thorough comprehension of the space geometry of the earthquake source boundaries and the adequacy of the attenuation relation in modelling the radiation pattern very important.  相似文献   

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