The scope of this study is to analyze some aspects of the Algerian earthquake catalogue between 1980 and 2009.Seismicity analysis is based on reliable compilation of earthquake catalogs obtained from different agencie...The scope of this study is to analyze some aspects of the Algerian earthquake catalogue between 1980 and 2009.Seismicity analysis is based on reliable compilation of earthquake catalogs obtained from different agencies.All intensities and magnitudes were converted to Ms magnitude using appropriate relationships.Dependent events were removed using adapted time and space windows.In addition,the completeness of the catalogue as a function of magnitude was determined from the standard deviation of occurrence rate plots,using the Stepp’s methodology.The remaining 2,016 independent earthquakes with Ms 2.2 were used to obtain various parameters(b-value,z-value)to characterize the temporal and spatial seismic activity for the entire northern part of Algeria.Finally,the obtained results are discussed to explain parameters variability.展开更多
Influenced by the layout of seismic network and the location of earthquakes,earthquake catalogs are often incomplete;such incompleteness of earthquake catalogue directly affects the analysis of sequence activity chara...Influenced by the layout of seismic network and the location of earthquakes,earthquake catalogs are often incomplete;such incompleteness of earthquake catalogue directly affects the analysis of sequence activity characteristics.In this paper,the GPU-acceleration-based g template matching method is used to scan the continuous waveforms of Chang Island earthquake swarm in Shandong Province from February 9 to August 20,2017.In total,15,286 earthquakes events were detected,which was more than 6 times compared with those in network catalogue and thus reduced the magnitude of completeness from 1.0 to 0.5.Based on the intergrated catalogue of earthquakes,the characteristics of Chang Island earthquake swarm were then analyzed using the Epidemic Type Aftershock Sequences(ETAS)model.The stochastic components in the ETAS model are used as a proxy for possible earthquake triggered by external forces(fluids).The results show that the proportion of earthquakes triggered by external forces of Chang Island swarm increases gradually(from 31.9%to 63.5%)and then decreases.The latter stage of swarm development is mainly affected by the self-excitation of earthquakes,suggesting that the fluids play an important role in the development of the Chang Island swarm.However,the triggering intensity of fluids to microseismicity is divergent in different periods,which may be related to the process of fluid permeation.展开更多
The history of Botswana’s major seismic events has been initiated by two earthquakes that occurred on the 11th of September and 11th of October 1952 with ML Richter magnitudes of 6.1 and 6.7, respectively, in the Oka...The history of Botswana’s major seismic events has been initiated by two earthquakes that occurred on the 11th of September and 11th of October 1952 with ML Richter magnitudes of 6.1 and 6.7, respectively, in the Okavango Delta Region (ODR). Not much is known and well documented about the seismicity of a larger coverage of Botswana primarily because over the years, local seismic stations were biased to the north-western part of Botswana, to monitor the more seismogenic ODR. The objective of this study is to use data from the International Seismological Centre (ISC) bulletin for the period 1966-2012 to estimate the relative size distribution of seismic events (b-value), the rate of seismic activity (a-value), and associated stress condition prevailing in Botswana to assist in the quest of hazard mitigation. This study shows that micro-seismic activities of magnitude ranging from 1.3 to 5.7 are distributed not only on the northern part of Botswana, but also in other parts of the country such as the Southern (including Kweneng East and West), Central and Eastern Botswana. Based on 327 events extracted from data compiled by the ISC, the frequency-magnitude distribution (FMD) of earthquakes in Botswana from 1966 to 2012 was estimated with b-value and a-value for the entire catalogue found to be 1.2 and 6.3, respectively, implying a region of low stress dominated by small to moderate events. The minimum completeness magnitude (MC), a value that indicates the lowest magnitude above which all seismic events are reliably recorded was found to be 3.8. From this analysis, annual probabilities of occurrence for M4 and M5 events were found to be 67.2% and 4.3%, respectively, while M6 or larger event has an annual probability of 0.3%.展开更多
To determine the studying region of China Testing Center of the Collaboratory for the Study of Earthquake Predictability （CSEP）, we adopted the Entire-Magnitude-Range （EMR） method to study the spatial distribution...To determine the studying region of China Testing Center of the Collaboratory for the Study of Earthquake Predictability （CSEP）, we adopted the Entire-Magnitude-Range （EMR） method to study the spatial distribution of minimum magnitude of completeness （Mc） in the North-South Trending Seismic Belt （NSTSB） during the period from October 1, 2008 to May 31, 2011. Also bootstrap testing was performed to estimate the uncertainty of Mc, i. e. 8Mc. The results show that Mc （EMR） = 1.6 ± 0. 03 for the whole region. From the spatial distributions of Mc we find that Mc is in the range of Mu 1.3 ±2.0 for most regions. Specifically, the spatial distribution of Mc is consistent with the distribution of stations indicating high monitoring level in the southern part and low monitoring level in the northern part. Events located with less than three stations have great influence on Me. Moreover, the uncertainty of minimum magnitude of completeness 6Mc ranges from 0. 07 to 0.22. The spatial distribution of 6Mc agrees with the seismic rate. The shorter time span may cause larger 6Mc展开更多
Taking the northeast seismic zone as an example and based on the magnitude-frequency distribution principles of the G-R relationship and the study on the temporal and spatial distribution characteristics of the minimu...Taking the northeast seismic zone as an example and based on the magnitude-frequency distribution principles of the G-R relationship and the study on the temporal and spatial distribution characteristics of the minimum magnitude of completeness M C in each time interval,this paper makes a statistical analysis on the seismicity parameters of the research area and explores the influence of the completeness of small earthquake data on the seismicity parameters and seismic hazard analysis.It shows that the completeness analysis of the regional small earthquakes data provides a possible means for obtaining more accurate seismicity parameters that can better represent the actual regional seismicity level for areas of low seismicity.The research methods of this article and its conclusion can be used as a reference for the completeness analysis of earthquake data and seismic activity research.展开更多
本文将5种估计完备震级(magnitude of completeness,简记为Mc)的方法运用在三个不同模型产生的理论地震目录上,进而对比它们的优缺点.我们发现分段斜率中值分析法MBASS(The Median-based analysis of the segment slope)适用于不完备部...本文将5种估计完备震级(magnitude of completeness,简记为Mc)的方法运用在三个不同模型产生的理论地震目录上,进而对比它们的优缺点.我们发现分段斜率中值分析法MBASS(The Median-based analysis of the segment slope)适用于不完备部分台网探测地震能力随震级变化快及监测能力在时间上存在不均匀性(heterogeneity)的目录中,但是要求目录包含大量的地震事件,而b值稳定法MBS(The Mcby b-value stability approach)则适合用于台网探测地震能力随震级减小衰减慢地震目录,但是比较费时.最大曲率法MAXC(The Maximum Curvature technique)和拟合优度测试法GFT(The Goodness-of-Fit Test)在使用时都低估Mc,需要加调整量.完整性震级范围法EMR(Mcfrom Entire Magnitude Range)则一般给出比较稳定、适中的Mc估计值.这种方法适用在地震数目少,且对地震丢失容忍度比较高的情况.在实践中针对不同性质的地震目录,我们希望这项研究能帮助研究者选择最合适估计完备震级Mc的方法,并指出了一些估计完备震级中应当避免的问题.展开更多
文摘The scope of this study is to analyze some aspects of the Algerian earthquake catalogue between 1980 and 2009.Seismicity analysis is based on reliable compilation of earthquake catalogs obtained from different agencies.All intensities and magnitudes were converted to Ms magnitude using appropriate relationships.Dependent events were removed using adapted time and space windows.In addition,the completeness of the catalogue as a function of magnitude was determined from the standard deviation of occurrence rate plots,using the Stepp’s methodology.The remaining 2,016 independent earthquakes with Ms 2.2 were used to obtain various parameters(b-value,z-value)to characterize the temporal and spatial seismic activity for the entire northern part of Algeria.Finally,the obtained results are discussed to explain parameters variability.
基金sponsored by the National Key R&D Program of China(2016YFE0109300)the Seismological Science and Technology Spark Program(XH18026Y)+1 种基金Natural Science Foundation of Shandong Province(ZR2017QD014)Key R&D Program of Shandong Province(2016GSF120011)
文摘Influenced by the layout of seismic network and the location of earthquakes,earthquake catalogs are often incomplete;such incompleteness of earthquake catalogue directly affects the analysis of sequence activity characteristics.In this paper,the GPU-acceleration-based g template matching method is used to scan the continuous waveforms of Chang Island earthquake swarm in Shandong Province from February 9 to August 20,2017.In total,15,286 earthquakes events were detected,which was more than 6 times compared with those in network catalogue and thus reduced the magnitude of completeness from 1.0 to 0.5.Based on the intergrated catalogue of earthquakes,the characteristics of Chang Island earthquake swarm were then analyzed using the Epidemic Type Aftershock Sequences(ETAS)model.The stochastic components in the ETAS model are used as a proxy for possible earthquake triggered by external forces(fluids).The results show that the proportion of earthquakes triggered by external forces of Chang Island swarm increases gradually(from 31.9%to 63.5%)and then decreases.The latter stage of swarm development is mainly affected by the self-excitation of earthquakes,suggesting that the fluids play an important role in the development of the Chang Island swarm.However,the triggering intensity of fluids to microseismicity is divergent in different periods,which may be related to the process of fluid permeation.
文摘The history of Botswana’s major seismic events has been initiated by two earthquakes that occurred on the 11th of September and 11th of October 1952 with ML Richter magnitudes of 6.1 and 6.7, respectively, in the Okavango Delta Region (ODR). Not much is known and well documented about the seismicity of a larger coverage of Botswana primarily because over the years, local seismic stations were biased to the north-western part of Botswana, to monitor the more seismogenic ODR. The objective of this study is to use data from the International Seismological Centre (ISC) bulletin for the period 1966-2012 to estimate the relative size distribution of seismic events (b-value), the rate of seismic activity (a-value), and associated stress condition prevailing in Botswana to assist in the quest of hazard mitigation. This study shows that micro-seismic activities of magnitude ranging from 1.3 to 5.7 are distributed not only on the northern part of Botswana, but also in other parts of the country such as the Southern (including Kweneng East and West), Central and Eastern Botswana. Based on 327 events extracted from data compiled by the ISC, the frequency-magnitude distribution (FMD) of earthquakes in Botswana from 1966 to 2012 was estimated with b-value and a-value for the entire catalogue found to be 1.2 and 6.3, respectively, implying a region of low stress dominated by small to moderate events. The minimum completeness magnitude (MC), a value that indicates the lowest magnitude above which all seismic events are reliably recorded was found to be 3.8. From this analysis, annual probabilities of occurrence for M4 and M5 events were found to be 67.2% and 4.3%, respectively, while M6 or larger event has an annual probability of 0.3%.
基金jointly sponsored by the Youth Fund Progamm of the National Natural Science Foundation of China ( 40804010 )the Central-level Basic Science Programm of Institute of Geophysics,CEA (DQJB10B23)
文摘To determine the studying region of China Testing Center of the Collaboratory for the Study of Earthquake Predictability （CSEP）, we adopted the Entire-Magnitude-Range （EMR） method to study the spatial distribution of minimum magnitude of completeness （Mc） in the North-South Trending Seismic Belt （NSTSB） during the period from October 1, 2008 to May 31, 2011. Also bootstrap testing was performed to estimate the uncertainty of Mc, i. e. 8Mc. The results show that Mc （EMR） = 1.6 ± 0. 03 for the whole region. From the spatial distributions of Mc we find that Mc is in the range of Mu 1.3 ±2.0 for most regions. Specifically, the spatial distribution of Mc is consistent with the distribution of stations indicating high monitoring level in the southern part and low monitoring level in the northern part. Events located with less than three stations have great influence on Me. Moreover, the uncertainty of minimum magnitude of completeness 6Mc ranges from 0. 07 to 0.22. The spatial distribution of 6Mc agrees with the seismic rate. The shorter time span may cause larger 6Mc
基金Fund for the research was granted from Institute of Crustal Dynamics,China Earthquake Administration(No.ZDJ2013-05)and(No.ZDJ2010-20)
文摘Taking the northeast seismic zone as an example and based on the magnitude-frequency distribution principles of the G-R relationship and the study on the temporal and spatial distribution characteristics of the minimum magnitude of completeness M C in each time interval,this paper makes a statistical analysis on the seismicity parameters of the research area and explores the influence of the completeness of small earthquake data on the seismicity parameters and seismic hazard analysis.It shows that the completeness analysis of the regional small earthquakes data provides a possible means for obtaining more accurate seismicity parameters that can better represent the actual regional seismicity level for areas of low seismicity.The research methods of this article and its conclusion can be used as a reference for the completeness analysis of earthquake data and seismic activity research.
