Simulation of Seismicity in the Block-structure Model of Italy and its Surroundings     

A. Peresan  I. Vorobieva  A. Soloviev  G. F. Panza 《Pure and Applied Geophysics》2007,164(11):2193-2234

The numerical block-model of the lithosphere dynamics is used to simulate seismicity in Italy and its surroundings, based on the available structural and geodynamics information. The purpose of the study is to understand which are the tectonic processes that control the main features of the observed seismicity and the kinematics of the region. The influence of the rheology of the fault systems is studied as well. The model we use differs from other modeling approaches in that it simulates earthquakes and hence it possibly relates to seismicity and geodynamics. The model provides an effective capability to include the set of documented constraints supplied by widely available earthquake catalogs. This is done by means of the comparison of the GR relation, of the focal mechanisms and of the space distribution for observed and computed seismicity. The region is modeled as a system of perfectly rigid blocks, separated by infinitely thin fault planes, in viscoelastic interaction between themselves and with the underlying medium. The movement of the boundary blocks and of the underlying medium determines the motion of the blocks. The synthetic seismicity obtained with the defined block-model is similar to the observed one for the most seismically active areas. A linear frequency-magnitude (FM) relation (Gutenberg-Richter law) is obtained for synthetic earthquakes; the slope (b-value) of the FM plot appears larger for the synthetic seismicity than for the observed one. Nevertheless, the b-value is essentially larger in northern and central Italy than that in southern Italy, both in the model and in the observations. The analysis of the source mechanisms of the synthetic earthquakes shows a good agreement with the observations. In the model normal faulting is typical for the Apennines, the eastern edge of Sicily and the Calabrian arc, while reverse faulting takes place at the northwestern boundary of the Adriatic Sea, in the southern Alps and along the eastern edge of the Adria, along the Dinarides. The model correctly reproduces the extension zone along the Apennines and the contraction zone along the northwestern boundary of the Adriatic Sea; the counter-clockwise rotation of the Adria is mimed. The resulting movements of the blocks are in overall agreement with GPS (Global Positioning System) observations. The results of the modeling experiments suggest that the main features of dynamics and seismicity in the central Mediterranean region cannot be satisfactorily explained as a consequence of Africa and Eurasia convergence only; the passive subduction in the Calabrian arc and the different rheology of faults are essential as well.  相似文献   

The tsunami threat on the Mexican west coast: A historical analysis and recommendations for hazard mitigation     

Salvador F. Farreras  Antonio J. Sanchez 《Natural Hazards》1991,4(2-3):301-316

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Maximum Likelihood Estimation of Seismic Hazard for Sweden     

Andrzej Kijko  Efthimios Skordas  Rutger Wahlström  Päivi Mäntyniemi 《Natural Hazards》1993,7(1):41-57

The maximum magnitude, the activity rate, and the Gutenberg-Richterb parameter as earthquake hazard parameters, have been evaluated for Sweden. The maximum likelihood method permits the combination of historical and instrumental data. The catalog used consists of 1100 earthquakes in the time interval 1375–1989. The extreme part of the catalog contains only the strongest historical earthquakes, whereas the complete part is divided into several subcatalogs, each assumed complete above a specified threshold magnitude. The uncertainty in magnitude determination was taken into account. For southern Sweden, the calculations giveb-values of 1.04 (0.05) for the whole area south of 60° N and 0.98 (0.06) for a subregion of enhanced seismicity in the Lake Vänern area. For the whole area north of 60° N, theb-value is 1.35 (0.06) and for the seismicity zone along the Gulf of Bothnia 1.26 (0.06). The number of annually expected earthquakes with magnitude equal to or larger than 2.4 [M_L(UPP) or M_M(UPP)] is 1.8 for the whole southern Sweden, 1.3 for the Lake Vänern region, 3.7 for northern Sweden, and 2.4 for the region along the Gulf of Bothnia. The maximum expected regional magnitude is calculated to 4.9 (0.5) for a time span of 615 years for southern Sweden and the Lake Vänern subregion, and 4.3 (0.5) for a time span of 331 years for northern Sweden and the Gulf of Bothnia subregion. However, several historical earthquakes with magnitude above 5 in nearby areas of Norway indicate that the seismic potential may be higher.  相似文献   

中国大陆及周缘地震目录完整性统计分析   总被引：4，自引：1，他引：3       下载免费PDF全文

徐伟进  高孟潭 《地球物理学报》2014,57(9):2802-2812

地震目录资料是进行地震预测、地震危险性分析、地震活动性研究等地震学研究的基础资料.对地震目录资料的完整性可靠性分析是地震学研究的基础工作之一.近几十年来我国积累的大量的仪器地震记录,历史地震也在不断更新,为地震活动性研究提供了更为丰富的样本,因此有必要对新的地震目录进行完整性分析.本文采用了新的统计方法对我国仪器记录地震目录和历史破坏性地震目录进行了完整性分析.结果表明,对于仪器记录地震目录（M≥3.0）我国东部地区1975年后基本完整,西部地区1980年后基本完整.对于历史地震目录（M≥5.0）,东部地区1500年后基本完整,西部地区1950年后基本完整.考虑到华北地震区历史破坏性地震（M≥4³/₄）活动的时间非平稳性,我们采用突变点分析法研究了华北地震区历史破坏性地震目录的时间特征,得到了华北地震区地震活动周期性变化的突变点位置,并揭示了华北地震区历史破坏性地震目录完整起始时间约为公元1500年前后.  相似文献   

两种地震预警定位方法的比较     

李军 《中国地震研究》2014,(4):502-509

In this paper, according to the Fujian Seismic Network earthquake catalog records, the Tnow method and the Four Stations Continuous Location method （hereinafter called FSCL） put forward by Jin Xing are inspected by using P-wave arrival information of the first four stations of each seismic event. Results show that for earthquakes within the network, both methods can obtain similar location results and location deviations are small for the majority of the events. For earthquakes outside the network, the location deviation may be amplified as the epicentral distance increases, owing to the seismic station distribution which spread toward the side of the epicenter and the small opening angle between seismic stations used for locating and epicenter. For the FSCL method, the impacts of the wave velocity on the location results may be significant for earthquakes outside the network. Thus, selecting a velocity model which is similar to the actual structure of the wave velocity will contribute to improving location results of earthquakes. The FSCL method can locate more seismic events than the Tnow method. It concludes that the Tnow method makes use of mistake information from some non-triggering stations in earthquake catalog, and some P-wave arrivals are not included in the earthquake catalog due to discontinuous records or unclear records of the seismic phase, which induces incorrect location.  相似文献   

多源海量统计遥感数据集成管理技术研究   总被引：1，自引：0，他引：1  

方利  姚敏  岳建伟  余卓渊 《地理信息世界》2010,8(1):56-60

统计遥感业务是国家统计局基于统计业务对空间信息的发展和应用需求,将GIS、RS和GPS空间信息技术全面应用于统计数据的获取、管理与分析中,从而提高统计效率和统计科技含量,构建新型国家统计业务体系。统计遥感业务数据具有多源、海量的特点,实现统计遥感数据的集成与管理是新型统计遥感业务成功运转的基础。针对统计遥感业务及数据应用需求,通过对各类空间数据集成与管理技术进行研究,提出在建立统计遥感空间数据库基础上,将影像以县级为单位进行拼接、然后压缩存储到统计遥感空间数据库,同时结合影像编目技术实现海量遥感影像的管理;提出将元数据管理和数据转换、数据直接访问以及数据互操作方式,实现多源统计遥感数据的集成与管理。通过多种方式,从应用层面较好地解决了海量、多源统计遥感数据的集成与管理,提升了统计遥感数据的应用范围。  相似文献   

Comparing different models of aftershock rate decay: The role of catalog incompleteness in the first times after main shock   总被引：2，自引：0，他引：2  

Barbara Lolli  Paolo Gasperini   《Tectonophysics》2006,423(1-4):43

We evaluated the efficiency of various models in describing the time decay of aftershock rate of 47 simple sequences occurred in California (37) from 1933 to 2004 and in Italy (10) from 1976 to 2004. We compared the models by the corrected Akaike Information Criterion (AIC_c) and the Bayesian Information Criterion (BIC), both based on the log-likelihood function and also including a penalty term that takes into account the number of independent observations and of free parameters of each model. These criteria follow two different approaches (probabilistic and Bayesian respectively) well covering the wide spectra of current views on model comparison. To evaluate the role of catalog incompleteness in the first times after the main shock, we compared the performance of different models by varying the starting time T_s and the minimum magnitude threshold M_min for each sequence. We found that Omori-type models including parameter c are preferable to those not including it, only for short T_s and low M_min while the latters generally perform better than the formers for T_s longer than a few hours and M_min larger than the main shock magnitude M_m minus 3 units. For T_s > 1 day or M_min > M_m − 2.5, only about 15% of the sequences still give a preference to models including c. This clearly indicates that a value of parameter c different from zero does not represent a general property of aftershock sequences in California and Italy but it is very likely induced in most cases by catalog incompleteness in the first times after the main shock. We also considered other models of aftershock decay proposed in the literature: the Stretched Exponential Law in two forms (including and not including a time shift) and the band Limited Power Law (LPL). We found that such models perform worse than the Modified Omori Model (MOM) and other Omori-type models for the large majority of sequences, although for LPL, the relatively short duration of the analyzed sequences (one year) might also contribute to its poor performance. Our analysis demonstrates that the MOM with c kept fixed to 0 represent the better choice for the modeling (and the forecasting) of simple sequence behavior in California and Italy.  相似文献   

A catalog of aftershock sequences in Greece (1971–1997): Their spatial and temporal characteristics     

George Drakatos  John Latoussakis 《Journal of Seismology》2001,5(2):137-145

A complete catalog of aftershock sequences is provided for main earthquakes with M_L 5.0, which occurred in the area of Greece and surrounding regions the last twenty-seven years. The Monthly Bulletins of the Institute of Geodynamics (National Observatory of Athens) have been used as data source. In order to get a homogeneous catalog, several selection criteria have been applied and hence a catalog of 44 aftershock sequences is compiled. The relations between the duration of the sequence, the number of aftershocks, the magnitude of the largest aftershock and its delay time from the main shock as well as the subsurface rupture length versus the magnitude of the main shock are calculated. The results show that linearity exists between the subsurface rupture length and the magnitude of the main shock independent of the slip type, as well as between the magnitude of the main shock (M) and its largest aftershock (Ma). The mean difference M–Ma is almost one unit. In the 40% of the analyzed sequences, the largest aftershock occurred within one day after the main shock.The fact that the aftershock sequences show the same behavior for earthquakes that occur in the same region supports the theory that the spatial and temporal characteristics are strongly related to the stress distribution of the fault area.  相似文献   

多源海量统计遥感数据集成管理技术研究     

方利  姚敏  岳建伟  余卓渊 《测绘软科学研究》2010,(1):56-60

统计遥感业务是国家统计局基于统计业务对空间信息的发展和应用需求,将GIS、Rs和GPS空间信息技术全面应用于统计数据的获取、管理与分析中,从而提高统计效率和统计科技含量,构建新型国家统计业务体系。统计遥感业务数据具有多源、海量的特点,实现统计遥感数据的集成与管理是新型统计遥感业务成功运转的基础。针对统计遥感业务及数据应用需求,通过对各类空间数据集成与管理技术进行研究,提出在建立统计遥感空间数据库基础上,将影像以县级为单位进行拼接、然后压缩存储到统计遥感空间数据库,同时结合影像编目技术实现海量遥感影像的管理;提出将元数据管理和数据转换、数据直接访问以及数据互操作方式,实现多源统计遥感数据的集成与管理。通过多种方式,从应用层面较好地解决了海量、多源统计遥感数据的集成与管理,提升了统计遥感数据的应用范围。  相似文献   

地震巨灾模型中的随机地震事件集模拟          下载免费PDF全文

徐伟进  高孟潭  左惠强 《地震工程学报》2020,42(4):1024-1034

地震巨灾保险是降低地震灾害风险的有效手段之一,而地震危险性分析是地震巨灾模型的主要分析模块之一。传统的概率地震危险性分析主要是基于潜在震源模型、地震活动性模型和地震动衰减模型等并采用概率方法得到场点的地震危险性值,该危险性表示的是未来所有地震对场点的综合影响。然而,在使用地震巨灾模型进行地震风险分析时需要用到单个地震事件对场点的影响,这就需要根据潜在震源区生成一系列单个地震事件,并计算每个事件对场点的影响。本研究采用蒙特卡洛方法,基于第五代中国地震动参数区划图中所采用的地震活动性模型(潜在震源区及其地震活动性参数),模拟符合我国地震活动时间、空间和强度分布特征的地震事件集。模拟时遵从的基本理论为:地震发生在时间上符合泊松分布,震级分布可用古登堡-里克特定律来描述,空间分布特征则用潜在震源区及其地震发生率来描述。模拟得到的地震事件包含以下参数:时间(年、月、日)、地点(经度、纬度)、深度、震级、断层走向以及衰减特征等。该模拟地震事件集可满足地震巨灾模型中地震风险分析的需求,已应用于我国地震巨灾模型中。  相似文献