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1.
Spatial sensitivity of seismic hazard results to different models with respect to background seismic activity and earthquake occurrence in time is investigated. For the contribution of background seismic activity to seismic hazard, background area source with uniform seismicity and spatially smoothed seismicity models are taken into consideration. For the contribution of faults, through characteristic earthquakes, both the memoryless Poisson and the time dependent renewal models are utilized. A case study, involving the assessment of seismic hazard for the Bursa province in Turkey, is conducted in order to examine quantitatively the influence of these models on seismic hazard results. The spatial variation of the difference in Peak Ground Acceleration (PGA) values obtained from these different models is presented in the form of difference maps for return periods of 475 and 2475 years. Best estimate seismic hazard maps for PGA and Spectral Accelerations (SA) at 0.2 and 1.0 s are obtained by using the logic tree method.  相似文献   

2.
Estimation of ground-motion amplitudes of different hazard levels is of paramount importance in planning of urban development of any metropolis. Such estimation can be computed through a probabilistic seismic hazard analysis (PSHA). This paper concentrates on the PSHA of an area located in Shiraz city, southern Iran. The area includes whole of Shiraz city (i.e., one of the largest and most populous cities of Iran) and its outskirts. Conventional and Monte Carlo simulation-based approaches are utilized to perform the PSHA of the studied area. Two areal seismic source models are delineated, and thence seismicity parameters of all zones associated with their corresponding uncertainties are computed. Uncertainties in ground-motion prediction are accounted for via three ground-motion prediction equations (GMPEs) within the logic tree framework. These GMPEs are applied to estimate bedrock ground shaking (Vs30?=?760 m/s) for several return periods (i.e., 75, 475, 975, and 2475 years). In general, the results of the two abovementioned PSHA approaches show relatively similar results. However, the Monte Carlo simulation-based approach overpredicts bedrock spectral accelerations at periods of 0.4–2.5 s compared to the conventional PSHA approach for return periods of 475, 975, and 2475 years.  相似文献   

3.
The earthquake risk on Romania is one of the highest in Europe, and seismic hazard for almost half of the territory of Romania is determined by the Vrancea seismic region, which is situated beneath the southern Carpathian Arc. The region is characterized by a high rate of occurrence of large earthquakes in a narrow focal volume at depth from 70 to 160 km. Besides the Vrancea area, several zones of shallow seismicity located within and outside the Romanian territory are considered as seismically dangerous. We present the results of probabilistic seismic hazard analysis, which implemented the “logic tree” approach, and which considered both the intermediate-depth and the shallow seismicity. Various available models of seismicity and ground-motion attenuation were used as the alternative variants. Seismic hazard in terms of macroseismic intensities, peak ground acceleration, and response spectra was evaluated for various return periods. Sensitivity study was performed to analyze the impact of variation of input parameters on the hazard results. The uncertainty on hazard estimates may be reduced by better understanding of parameters of the Vrancea source zone and the zones of crustal seismicity. Reduction of uncertainty associated with the ground-motion models is also very important issue for Romania.  相似文献   

4.
We examine the nature of the seismogenetic system along the San Andreas Fault (SAF), California, USA, by searching for evidence of complexity and non-extensivity in the earthquake record. We use accurate, complete and homogeneous earthquake catalogues in which aftershocks are included (raw catalogues), or have been removed by a stochastic declustering procedure (declustered catalogues). On the basis of Non-Extensive Statistical Physics (NESP), which generalizes the Boltzmann–Gibbs formalism to non-equilibrating (complex) systems, we investigate whether earthquakes are generated by an extensive self-excited Poisson process or by a non-extensive complex process. We examine bivariate cumulative frequency distributions of earthquake magnitudes and interevent times and determine the size and time dependence of the respective magnitude and temporal entropic indices, which indicate the level on non-equilibrium (correlation). It is shown that the magnitude entropic index is very stable and corresponds to proxy b-values that are remarkably consistent with the b-values computed by conventional means. The temporal entropic index computed from the raw catalogues indicate moderately to highly correlated states during the aftershock sequences of large earthquakes, progressing to quasi-uncorrelated states as these die out and before the next large event. Conversely, the analysis of the declustered catalogues shows that background seismicity exhibits moderate to high correlation that varies significantly albeit smoothly with time. This indicates a persistent sub-extensive seismogenetic system. The degree of correlation is generally higher in the southern SAF segment, which is consistent with the observation of shorter return periods for large earthquakes. A plausible explanation is that because aftershock sequences are localized in space and time, their efficient removal unveils long-range background interactions which are obscured by their presence! Our results indicate complexity in the expression of background seismicity along the San Andreas Fault, with criticality being a very likely mechanism as a consequence of the persistent non-equilibrium inferred from the temporal entropic index. However, definite conclusions cannot be drawn until the earthquake record is exhaustively studied in all its forms.  相似文献   

5.
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   

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.
Seismic hazard analysis requires knowledge of the recurrence rates of large magnitude earthquakes that drive the hazard at low probabilities of interest for seismic design. Earthquake recurrence is usually determined through studies of the historic earthquake catalogue for a given region. Reliable historic catalogues generally span time periods of 100–200 years in North America, while large magnitude events (M?≥?7) have recurrence rates on the order of hundreds or thousands of years in many areas, resulting in large uncertainty in recurrence rates for large events. Using Monte Carlo techniques and assuming typical recurrence parameters, we simulate earthquake catalogues that span long periods of time. We then split these catalogues into smaller catalogues spanning 100–200 years that mimic the length of historic catalogues. For each of these simulated “historic” catalogues, a recurrence rate for large magnitude events is determined. By comparing recurrence rates from one historic-length catalogue to another, we quantify the uncertainty associated with determining recurrence rates from short historic catalogues. The use of simulations to explore the uncertainty (rather than analytical solutions) allows us flexibility to consider issues such as the relative contributions of aleatory versus epistemic uncertainty, and the influence of fitting method, as well as lending insight into extreme-event statistics. The uncertainty in recurrence rates of large (M?>?7) events is about a factor of two in regions of high seismicity, due to the shortness of historic catalogues. This uncertainty increases greatly with decreasing seismic activity. Uncertainty is dependent on the length of the catalogue as well as the fitting method used (least squares vs. maximum likelihood). Examination of 90th percentile recurrence rates reveals that epistemic uncertainty in the true parameters may cause recurrence rates determined from historic catalogues to be uncertain by a factor greater than 50.  相似文献   

8.
任梦依  刘哲 《地震学报》2022,44(6):1035-1048
基于广义帕累托分布构建地震活动性模型,因其输入参数取值难以避免不确定性,导致依据该模型所得的地震危险性估计结果具有不确定性。鉴于此,本文选取青藏高原东北缘为研究区,提出了基于全域敏感性分析的地震危险性估计的不确定性分析流程和方法。首先,利用地震活动性广义帕累托模型,进行研究区地震危险性估计;然后,选取地震记录的起始时间和震级阈值作为地震活动性模型的输入参数,采用具有全域敏感性分析功能的E-FAST方法,对上述两个参数的不确定性以及两参数之间的相互作用对地震危险性估计不确定性的影响进行定量分析。结果表明：地震危险性估计结果（不同重现期的震级重现水平、震级上限及相应的置信区间）对两个输入参数中的震级阈值更为敏感;不同重现期的地震危险性估计结果对震级阈值的敏感程度不同;对不同的重现期而言,在影响地震危险性估计结果的不确定性上,两个输入参数之间存在非线性效应,且非线性效应程度不同。本文提出的不确定性分析流程和方法,可以推广应用于基于其它类型地震活动性模型的地震危险性估计不确定性分析。  相似文献   

9.
Over the years, several local and regional seismic hazard studies have been conducted for the estimation of the seismic hazard in Turkey using different statistical processing tools for instrumental and historical earthquake data and modeling the geologic and tectonic characteristics of the region. Recently developed techniques, increased knowledge and improved databases brought the necessity to review the national active fault database and the compiled earthquake catalogue for the development of a national earthquake hazard map. A national earthquake strategy and action plan were conceived and accordingly with the collaboration of the several institutions and expert researchers, the Revision of Turkish Seismic Hazard Map Project (UDAP-Ç-13-06) was initiated, and finalized at the end of 2014. The scope of the project was confined to the revision of current national seismic hazard map, using the state of the art technologies and knowledge of the active fault, earthquake database, and ground motion prediction equations. The following two seismic source zonation models are developed for the probabilistic earthquake hazard analysis: (1) Area source model, (2) Fault and spatial smoothing seismic source model (FSBCK). In this study, we focus on the development and the characterization of the Fault Source model, the background spatially smoothed seismicity model and intrinsic uncertainty on the earthquake occurrence-rates-estimation. Finally, PSHA results obtained from the fault and spatial smoothed seismic source model are presented for 43, 72, 475 and 2475 years return periods (corresponding to 69, 50, 10, and 2% probability of exceedance in 50 years) for PGA and 5% damped spectral accelerations at 0.2 and 1.0 s.  相似文献   

10.
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   

11.
Research on the principle and methodology of seismic zonation   总被引：1，自引：0，他引：1  
Based on the cognizance of the temporal-spatial inhomogeneity of seismicity in North China, adopting the results of earthquake prediction in the past two decades and the currently used methods of seismic hazard analysis, and after some zonation trials in North China, some improvements on the zonation principle and methodology were made:
  1. Seismic zones were taken as statistic units where seismicity parameters were obtained. Tendency analysis was introduced. Earthquake annual average occurrence rates were estimated corresponding to the seismicity level in the future period;
  2. Average annual earthquake occurrence rates for a given magnitude interval of a specific seismic zone were assigned to potential sources considering the relative risk level among these sources. Thus, the risk of great earthquakes can be estimated.
  3. The probabilistic spatial distribution function under the condition of magnitude interval was suggested to reflect the temporal and spatial inhomogeneity of seismicity.
  4. An orientation function in the seismic hazard analysis model was adopted, which reflects the real condition of earthquake foci in China.
  相似文献   

12.
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   

13.
Neo-deterministic seismic hazard assessment in North Africa   总被引：2，自引：2，他引：0  
North Africa is one of the most earthquake-prone areas of the Mediterranean. Many devastating earthquakes, some of them tsunami-triggering, inflicted heavy loss of life and considerable economic damage to the region. In order to mitigate the destructive impact of the earthquakes, the regional seismic hazard in North Africa is assessed using the neo-deterministic, multi-scenario methodology (NDSHA) based on the computation of synthetic seismograms, using the modal summation technique, at a regular grid of 0.2?×?0.2°. This is the first study aimed at producing NDSHA maps of North Africa including five countries: Morocco, Algeria, Tunisia, Libya, and Egypt. The key input data for the NDSHA algorithm are earthquake sources, seismotectonic zonation, and structural models. In the preparation of the input data, it has been really important to go beyond the national borders and to adopt a coherent strategy all over the area. Thanks to the collaborative efforts of the teams involved, it has been possible to properly merge the earthquake catalogues available for each country to define with homogeneous criteria the seismogenic zones, the characteristic focal mechanism associated with each of them, and the structural models used to model wave propagation from the sources to the sites. As a result, reliable seismic hazard maps are produced in terms of maximum displacement (D max), maximum velocity (V max), and design ground acceleration.  相似文献   

14.
This article presents site-specific probable seismic hazard of the Himachal Pradesh province, situated in a seismically active region of northwest Himalaya, using the ground motion relations presented in a companion article. Seismic recurrence parameters for all the documented probable sources are established from an updated earthquake catalogue. The contour maps of probable spectral acceleration at 0, 0.2, and 1 s (5% damping) are presented for 475 and 2475 years return periods. Also, the hazard curves and uniform hazard response spectrums are presented for all the important cities in this province. Results indicate that the present codal provision underestimates the seismic hazard at cities of Bilaspur, Shimla, Hamirpur, Chamba, Mandi, and Solan. In addition, regions near Bilaspur and Chamba exhibit higher hazard levels than what is reported in literature.  相似文献   

15.
In this paper, we propose to compare different declustering methods on the basis of the time-correlation and the space-clustering of the residual earthquake catalog after the declustering techniques have been applied. To this aim, we applied two point process clustering measures, the Allan Factor and the Morisita Index, for the identification and quantification of temporal correlation and spatial clustering in point processes, respectively. We used our joint space–time approach to study the earthquake space–time point processes of southern California and Switzerland with surrounding area, declustered by using the method of Gardner and Knopoff (with Grünthal and Uhmhammer window) and that of Reasenberg (with different setting parameters). Our results show that the residual declustered catalog is still characterized by time-correlated structures at long timescales; however, the cutoff timescale that is the lowest timescale above which the time-correlation is visible is higher with the Reasenberg method while is smaller with the Gardner and Knopoff method with Grünthal window. The space-clustering analysis performed by means of the Morisita Index suggests that the declustering technique effectively reduces the spatial clustering of the seismicity of Switzerland, but does not change the spatial properties of the residual seismic catalogue of the southern California.  相似文献   

16.
川滇地区是我国地震危险性较高的地区之一.本文基于对特大强震的风险性考虑,使用全球地震模型OpenQuake软件,建立了川滇地区地震危险性预测新模型.首先根据构造特征划分多个震源分区,并整理出这些震源分区内断层活动特征与滑动速率;基于震源分区和断层模型,使用GPS应变率转换成的锥形古登堡-里克特关系作为整个区域的地震积累率,并允许超过历史最大震级的特大地震的出现,结合活动断层滑动速率所积累的地震发生率,给出震源分区内断层地震源和背景地震源的地震发生率的比率分配关系;在活动断层分段上,保留了大型断裂或其主要部分,没有根据小的阶区来对断层进行详细分段,以便分配特大地震发生率;并使用地震率平滑方法分配背景地震发生率.最后在OpenQuake中加入地震动预测方程,计算出了川滇地区的PGA分布图,为区域地震危险性提供科学依据.  相似文献   

17.
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   

18.
To investigate the characteristics of earthquake hazard parameters as a means of identifying different zones of seismicity, we have compiled a catalogue of about 1850 moderate to large-sized earthquakes with magnitudes m4.0 or greater in southern Turkey for the time period from 1900 to 1990. Several methods have been applied to the earthquake catalogue to assess seismic hazard. The study area is divided into 77 overlapping cells of 2° size. Theoretical calculations were made for the prediction of maximum magnitude, intensity, b-values, strain energy release and corresponding m3 and peak ground acceleration levels for a given period of time. The resultant seismic hazard for each parameter is depicted as a contour map to indicate lateral variations in areas of seismic source. A combination and evaluation of various hazard parameters resulted in more reasonable estimates of hazard. It is found that the most hazardous seismic zones are the Rhodes and Burdur zones where the level of peak ground acceleration reaches up to 280 cm s-2 for an average return period of 100 years.  相似文献   

19.
苏门答腊岛8.7级地震对我国南北地震带地震形势的影响   总被引：3，自引：0，他引：3  
分析了苏门答腊8．7级地震对我国南北地震带尤其是川滇地震活动和前兆观测的巨大影响，以及历史上从印度安达曼到印度尼西亚苏门答腊区域的巨大地震与中国大陆西部尤其是南北地震带强震的关系。结果表明：这次苏门答腊8．7级地震对南北地震带地震活动和前兆观测的影响巨大；历史上安达曼—苏门答腊区域的巨大地震与中国大陆西部尤其是南北地震带强震存在较短时间尺度的呼应相关。  相似文献   

20.
Based on existing historical data and observations from the Dalian seismic station,this paper rechecks the parameters of the three historical earthquakes of 1916,1917 and 1944 in the North Yellow Sea,near the Yalu River region.The results show that their relocated epicenters are located at contemporarily intense seismic active zones,consistent with the results derived from the data of the Dalian seismic station.The results are valuable in both revising earthquake catalogues and understanding the local background seismicity.  相似文献   

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