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1.
The diurnal periodicity of seismic events of different energy from the Greece earthquake catalog was studied. Earthquake samplings of different energy with a known level of magnitude of completeness were compiled. Parameters of the diurnal periodicity of earthquakes in different time and magnitude intervals were analyzed. Significant diurnal periodicity of earthquakes with M ≤ 4.1 was revealed. The most important result of the paper is the discovery of the diurnal periodicity of the representative earthquakes with M = 3.2–4.1. The diurnal periodicity of representative earthquakes cannot be explained at the base of the prevailing hypothesis considering the diurnal periodicity of earthquakes as an apparent phenomenon resulting from diurnal changes in the real sensitivity of the seismic network due to diurnal variations of seismic noise. 相似文献
2.
L. L. Romachkova V. G. Kossobokov G. F. Panza G. Costa 《Pure and Applied Geophysics》1998,152(1):37-55
—Large earthquakes in Italy are preceded by a specific seismic activation which could be diagnosed by a reproducible intermediate-term earthquake prediction method—a modification for lower seismic rate areas of the algorithm, known as M8 (Keilis-Borok and Kossobokov, 1990). Use has been made of the PFG-ING catalog of earthquakes, compiled on a regular basis, to determine areas and times of increased probability for occurrences of M≥ 6 earthquakes. In retroactive simulation of forward prediction, for the period 1972–1995, both the 1976 Friuli, M = 6.1 and the 1980 Irpinia, M = 6.5 earthquakes are predicted. In the experiment where priority magnitude scale is used, the times of increased probability for a strong earthquake to occur (TIPs) occupy less than a quarter of the total magnitude-space-time domain, and are rather stable with respect to positioning of circles of investiga tion. Successful stability tests have been made considering a recently compiled catalog (CCI97) (Peresan et al., 1997). In combination with the CN algorithm results (Costa et al., 1996) the spatio-temporal uncertainty of the prediction could be reduced to 5%. The use of M8 for the forward prediction requires the computations to be repeated each half-year, using the updated catalog. 相似文献
3.
The paper presents the current state of magnitude estimation for Koyna earthquakes exceeding magnitude 3.0. We estimate coda duration magnitude from analogue seismograms recorded on the short period vertical (SPZ) seismometer at Hyderabad seismic observatory HYB and determine moment magnitude using very broad-band (VBB) data from the Geoscope station (HYB)and short period digital data from the local seismic network of NationalGeophysical Research Institute (NGRI) around the Koyna and Warna reservoirs.Firstly, the seismograms of 97 Koyna earthquakes exceeding magnitude 4.0 havebeen used to establish a new empirical coda duration magnitude scale which includes the higher order terms of log10, where is the coda length in seconds. Four background noise levels (1, 2, 6 and 10 mm) areconsidered to estimate the coda duration. We found that the duration magnitudes for 1 mm background level are more stable than those for 2, 6 and 10 mm. The new coda duration magnitude (Mdnew) scale, for 1 mmlevel, is:Mdnew = –0.594 + 2.04 log10 – 0.0435 (log10)2The estimated Mdnew are compatible with the reported MS values of the NGRI observatory and the mb values of the United States Geological Survey (USGS). These magnitudes can be obtained within the standard deviation of ± 0.26 units of MS (NGRI). A new relatively homogeneous catalog for Koyna earthquakes of Mdnew 4.0 is obtained. The momentmagnitudes for 34 Koyna-Warna events of Mdnew ranging from 3.0 to 5.4 have been estimated using two techniques. The first utilizes amplitudes of band-pass filtered (between 15 and 30 sec) velocity traces of moderate Koyna-Warna earthquakes of MW} 4.4 to 5.4, we abbreviate the magnitude using MA. The second is based on the S-wave spectrum of short period seismograms of local earthquakes (MW < 3.8). Moment magnitudes estimated by spectral analysis mainly depend on the estimation of event's long-period spectral level and appears to saturate for moderate Koyna-Warnaearthquakes (MW > 3.8). We recommend the use of both techniques whenever possible. The estimated moment magnitudes and Mdnew show an almost linear relationship with a standard deviation of ± 0.05. 相似文献
4.
The paper addresses the collection and analysis of new data on aftershocks that occurred within 20 days of the main shock of the December 7, 1988, Spitak earthquake, Mw = 6.8. The data were used to improve the location of aftershock hypocenters and magnitudes. Available data concerning this 20-day period were the least reliable in terms of completeness, representativeness, and the accuracy of hypocenter location and, in particular, estimation of energy classes and magnitudes. New data were retrieved from the records and bulletins of the seismic stations of the regional and global networks. Hypocenter parameters were determined by means of the minimization of wave travel-time residuals and subsequent double-difference hypocenter relocation. Digital records of the Obninsk and Arti seismic stations (Δ = 15°–18°) and five more distant stations (Δ = 34°–53°) were used to more accurately estimate the surface-wave magnitude of the main shock and strongest aftershock. The aftershock catalog of the Spitak earthquake was substantially revised. First, the previous hypocenter locations (Aref’ev et al., 1991) were improved using the double-difference method; second, new data were retrieved from the bulletins of Caucasian seismic stations. The minimum magnitude of completeness (M c = 1.9) of the new catalog for the first 20 days after the main shock (when there were no epicentral observations) is the same as that for the period from December 7, 1988, to December 31, 1989. The new catalog contains information on 2090 aftershocks with magnitude M = 1.9 and more for the period from December 7, 1988, to December 31, 1989. The double-difference method allowed the location of the epicenters of clustered earthquakes to be reliably estimated with a longitude error of no more than 4.6 km, a latitude error of 4 km, and a depth error of 5 km. The new spatial distribution of the aftershock hypocenters is better correlated with the tectonic setting than the old data. The new catalog can be used to assess seismic hazard after strong earthquakes in the region. 相似文献
5.
Universality of the Seismic Moment-frequency Relation 总被引：1，自引：0，他引：1
Y. Y. Kagan 《Pure and Applied Geophysics》1999,155(2-4):537-573
—We analyze the seismic moment-frequency relation in various depth ranges and for different seismic regions, using Flinn-Engdahl's regionalization of global seismicity. Three earthquake lists of centroid-moment tensor data have been used the Harvard catalog, the USGS catalog, and the Huang et al. (1997) catalog of deep earthquakes. The results confirm the universality of the β-values and the maximum moment for shallow earthquakes in continental regions, as well as at and near continental boundaries. Moreover, we show that although fluctuations in earthquake size distribution increase with depth, the β-values for earthquakes in the depth range of 0–500 km exhibit no statistically significant regional variations. The regional variations are significant only for deep events near the 660 km boundary. For declustered shallow earthquake catalogs and deeper events, we show that the worldwide β-values have the same value of 0.60 ± 0.02. This finding suggests that the β-value is a universal constant. We investigate the statistical correlations between the numbers of seismic events in different depth ranges and the correlation of the tectonic deformation rate and seismic activity (the number of earthquakes above a certain threshold level per year). The high level of these correlations suggests that seismic activity indicates tectonic deformation rate in subduction zones. Combined with the universality of the β-value, this finding implies little if any variation in maximum earthquake seismic moment among various subduction zones. If we assume that earthquakes of maximum size are similar in different depth ranges and the seismic efficiency coefficient, χ, is close to 100% for shallow seismicity, then we can estimate χ for deeper earthquakes for intermediate earthquakes χ≈ 5%, and χ≈ 1% for deep events. These results may lead to new theoretical understanding of the earthquake process and better estimates of seismic hazard. 相似文献
6.
中强地震序列的主震发生后,短时间内受台站距震中较远、尾波干扰和波形重叠等因素的影响,往往会遗漏大量的地震,而地震目录的完整性会直接影响到震后趋势判定和余震序列特征分析的科学性和可靠性。本文利用基于GPU加速的模板匹配方法对2017年8月1～12日的连续波形进行扫描计算,检测九寨沟MS7.0地震前后遗漏的地震事件,选取台网目录中信噪比较高的1033个地震事件作为模板,在主震前7天至震后5天期间识别出4854个检测地震事件,为台网可定位目录的3.3倍,除去对台网单台地震事件的修正外,还检测到1797个遗漏地震事件,将完备震级从1.6级降低到1.4级。基于补充了遗漏地震的完整地震目录,对2017年8月8日九寨沟MS7.0地震序列活动特征进行分析。结果表明,前震序列在主震前短时间内出现了地震活动的密集增强,b值也显示为低值状态,可能是深部断层发生破裂之前的加速蠕动的结果。随着时间的推移,余震序列的完备震级逐渐下降并趋于稳定,b值存在缓慢升高的趋势,未来较长时期内余震序列仍将处于持续衰减的状态。 相似文献
7.
利用新疆地震台网及其毗邻地区的国外地震台站提供的地震Ｐ波到时数据，重建了新疆及其毗邻地区地壳上地幔的三维速度图像．主要结果是：１．研究区地壳上地幔的地震波速度存在明显的横向不均匀性．这种不均匀性出现在不同构造单元之间，也出现在各构造单元之内．２．一般来说，研究区域内盆地是上地幔的隆起区，褶皱系是上地幔的坳陷区．３．岩石层厚度和软流层的深度与全球的平均结果有较大不同．４．海洋岩石层或大陆岩石层板块在兴都库什和克什米尔与中国交界地区的消减明显存在．５．地壳上地幔物质运动比较剧烈，有部分熔融物质上涌到地壳中部或更浅的深度． 相似文献
8.
不同标度震级关系和台基影响问题探讨 总被引：2，自引：1，他引：2
利用近年中国数字地震台网观测报告中的中国及邻区地震目录资料,取能够同时计算面波震级MS和近震震级ML的地震,拟合出2种震级之间的关系,发现与过去使用30余年的换算公式存在系统差别。考虑现代化地震数字观测系统有动态范围大、频带宽、台站多、覆盖区域广、测定精度高的特点,由此拟合的关系应当更可靠。考虑不同误差因素统计面波震级MS和近震震级ML的关系表明,2种震级之间换算和不换算的差别并不大,因此建议MS和ML震级之间不换算为宜。分析地震台站的场地响应发现:一些基岩台的放大因子在1附近,场地响应不随频率变化;处于沉积土层的台站,放大因子在低频段大于1,高频段小于1;还有一些台站在某个频段范围大于1,或者小于1。另外,沉积土层台站的单台震级和台网平均震级差也随周期增大,呈现由负到正的增长趋势。看来并不存在固定的台站校正系数,因此不能把台站校正作为提高震级测定精度的方法。 相似文献
9.
A. B. Baba E. E. Papadimitriou B. C. Papazachos C. A. Papaioannou B. G. Karakostas 《Pure and Applied Geophysics》2000,157(5):765-783
10.
Study on the Moment Magnitude of Small and Moderate Earthquakes Located in the Inner Mongolia Region
Based on digital seismic waveform data from Inner Mongolia Digital Seismic Network, the source spectrum parameters of 182 small and moderate earthquakes from January, 2009 to September, 2016 are derived, and the seismic moment M0 and moment magnitude MW of the earthquakes are calculated. The ML-MW relationship and the relationship between stress drop and magnitude are obtained using the linear regression method. It is clear that incorporating the moment magnitude into the seismic quick report catalog and the official earthquake catalog can enrich earthquake observation report content, thus providing better service for earthquake emergency and earthquake scientific research. 相似文献
11.
The first step in any seismic hazard study is the definition of seismogenic sources and the estimation of magnitude-frequency relationships for each source. There is as yet no standard methodology for source modeling and many researchers have worked on this topic. This study is an effort to define linear and area seismic sources for Northern Iran. The linear or fault sources are developed based on tectonic features and characteristic earthquakes while the area sources are developed based on spatial distribution of small to moderate earthquakes. Time-dependent recurrence relationships are developed for fault sources using renewal approach while time-independent frequency-magnitude relationships are proposed for area sources based on Poisson process. GIS functionalities are used in this study to introduce and incorporate spatial-temporal and geostatistical indices in delineating area seismic sources. The proposed methodology is used to model seismic sources for an area of about 500 by 400 square kilometers around Tehran. Previous researches and reports are studied to compile an earthquake/fault catalog that is as complete as possible. All events are transformed to uniform magnitude scale; duplicate events and dependent shocks are removed. Completeness and time distribution of the compiled catalog is taken into account. The proposed area and linear seismic sources in conjunction with defined recurrence relationships can be used to develop time-dependent probabilistic seismic hazard analysis of Northern Iran. 相似文献
12.
为了由过去的地震活动性推测将来的地震活动性,引入了地震（震级≥m）的期望年发生率v（≥m）来描述一个地区的地震活动性．根据全球地震目录（1964-1994年）以及南加州（1932-1995年）和华北（1970-1994年）两个区域地震目录资料,以统计样本量作为目录记录时间长短的相对量度,对由不同的统计样本量计算得出的地震实际年发生率v（≥m,T,t）进行了统计分析,得到三点结沦：①在统计样本量n足够大的情况下,地震实际年发生率表现出准平稳时间过程的特征,可近似地看作地震期望年发生率,本文给出了这种近似的误差（离差系数）与统计样本量之间的定量关系;②离差系数与统计样本量之间的关系与震级无关,表现出不同震级层次的相似性;③统计样本量相同时,不同震级的地震期望年发生率之间满足logv（≥）=a－bm的关系,形式上与G－R关系相似,但它给出了由小地震的统计特征估计大地震的期望年发生率及其统计误差的方法．基于上述结论,进一步讨论了地震活动性的统计特征在地震危险性分析中的潜在应用。 相似文献
13.
V. A. Saltykov Yu. A. Kugaenko N. M. Kravchenko A. A. Konovalova 《Journal of Volcanology and Seismology》2013,7(1):58-75
This paper presents a set of seismicity parameters that are estimated at the Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences based on the regional catalog data with the purpose of routine monitoring of the current seismic situation in the region. The focus is on the identification of changes in the seismic regime (seismic quiescences and seismicity increases) in earth volumes adjacent to the maturing rupture zone of a large earthquake. The techniques we use include estimation of the seismicity level for the region using the SOUS’09 scale; calculation of the variations in the slope of the recurrence relation, identification of statistically significant anomalies in the slope using the Z test, and calculation of the seismic activity A 10; monitoring the RTL parameter and variations in the area of seismogenic ruptures; using the Z test to detect areas of statistically significant decreases in the rate of seismicity; and identification of earthquake clusters. We furnish examples of such anomalies in these seismicity parameters prior to large earthquakes in Kamchatka. 相似文献
14.
Based on the earthquake catalog reported by the Chinese digital seismic network in recent years, we select the earthquakes with both surface wave magnitude and local magnitude and fit them into a relationship between the two magnitudes. The systematic difference is found from the formula which has been used for 30 years. Because of a large dynamic range and wide frequency range of the current digital observation system, in addition to a larger number of stations and earthquakes being used compared to before, the relation obtained in this paper seems more reliable. Our calculation shows that there is no significant difference before and after magnitude conversion so we suggest the abandonment of magnitude conversion. The site response of a station consists of amplification at different frequencies. The amplification is equal to about 1 and changes little with frequency at stations located on basement rock, and it is greater than 1 at low frequency ranges and less than 1 at high frequency ranges at stations located on sediment layers. The difference between magnitudes from single station located on sediment layer and the average magnitude from the whole network increases from negative to positive with period. It seems that there is no fixed station correction factor and the station correction method does not work to improve the accuracy and magnitude estimates. 相似文献
15.
G. A. Popandopoulos I. Baskoutas E. Chatziioannou 《Izvestiya Physics of the Solid Earth》2016,52(2):195-209
Spatiotemporal mapping the minimum magnitude of completeness Mc and b-value of the Gutenberg–Richter law is conducted for the earthquake catalog data of Greece. The data were recorded by the seismic network of the Institute of Geodynamics of the National Observatory of Athens (GINOA) in 1970–2010 and by the Hellenic Unified Seismic Network (HUSN) in 2011–2014. It is shown that with the beginning of the measurements at HUSN, the number of the recorded events more than quintupled. The magnitude of completeness Mc of the earthquake catalog for 1970–2010 varies within 2.7 to 3.5, whereas starting from April 2011 it decreases to 1.5–1.8 in the central part of the region and fluctuates around the average of 2.0 in the study region overall. The magnitude of completeness Mc and b-value for the catalogs of the earthquakes recorded by the old (GINOA) and new (HUSN) seismic networks are compared. It is hypothesized that the magnitude of completeness Mc may affect the b-value estimates. The spatial distribution of the b-value determined from the HUSN catalog data generally agrees with the main geotectonic features of the studied territory. It is shown that the b-value is below 1 in the zones of compression and is larger than or equal to 1 in the zones dominated by extension. The established depth dependence of the b-value is pretty much consistent with the hypothesis of a brittle–ductile transition zone existing in the Earth’s crust. It is assumed that the source depth of a strong earthquake can probably be estimated from the depth distribution of the b-value, which can be used for seismic hazard assessment. 相似文献
16.
Iranian earthquakes, a uniform catalog with moment magnitudes 总被引：3，自引：1，他引：2
Sepideh Karimiparidari Mehdi Zaré Hossein Memarian Andrzej Kijko 《Journal of Seismology》2013,17(3):897-911
A uniform earthquake catalog is an essential tool in any seismic hazard analysis. In this study, an earthquake catalog of Iran and adjacent areas was compiled, using international and national databanks. The following priorities were applied in selecting magnitude and earthquake location: (a) local catalogs were given higher priority for establishing the location of an earthquake and (b) global catalogs were preferred for determining earthquake magnitudes. Earthquakes that have occurred within the bounds between 23–42° N and 42–65° E, with a magnitude range of M W 3.5–7.9, from the third millennium BC until April 2010 were included. In an effort to avoid the “boundary effect,” since the newly compiled catalog will be mainly used for seismic hazard assessment, the study area includes the areas adjacent to Iran. The standardization of the catalog in terms of magnitude was achieved by the conversion of all types of magnitude into moment magnitude, M W, by using the orthogonal regression technique. In the newly compiled catalog, all aftershocks were detected, based on the procedure described by Gardner and Knopoff (Bull Seismol Soc Am 64:1363–1367, 1974). The seismicity parameters were calculated for the six main tectonic seismic zones of Iran, i.e., the Zagros Mountain Range, the Alborz Mountain Range, Central Iran, Kope Dagh, Azerbaijan, and Makran. 相似文献
17.
地震丛集的分形新方法—物理分形 总被引：3，自引：0，他引：3
地震时间丛集的传统分形分析方法把地震事件看作是时间轴上无质量的数学点。这些方法得到的结果主要反映了大量小地震的活动特征。本文发展了一个新的物理分形分析的筛子方法，采用一系列震级筛子来研究不同震级地震的分布特征。对华北和南加洲的研究结果表明，同一地区地震目录中不同震级范围的子集合具有近似相等的分维数，华北Ｄ＝０．３，南加洲Ｄ＝０．４。 相似文献
18.
杨智娴 《地震学报(英文版)》1999,12(6):659-666
IntroductionTaiwanlocatedinthecollisionboundalbetweentheEurasianandthePhilippineSeaplatesisoneofhighseismicityregionsintheworld.HundredsofearthquakeswithM25occurredperyearandmorethan40withM27since1900.Amongtheseevents,shalloweventswithdepthofseveraltensofkilometersandintermediate-deepeventswithdepthof100-200kinexistwhichrepresentsacharacterofthesubductionzone.ThemagnitudesofTaiwaneventslistedinthecatalogofChineseearthquakesaretakenfromsomehistoricaldocumentsandGutenbergandRichter'sworks(19… 相似文献
19.
F. Ramón Zúñiga Gerardo Suárez Ángel Figueroa-Soto Avith Mendoza 《Journal of Seismology》2017,21(6):1295-1322
The purpose of this work is to define a seismic regionalization of Mexico for seismic hazard and risk analyses. This seismic regionalization is based on seismic, geologic, and tectonic characteristics. To this end, a seismic catalog was compiled using the more reliable sources available. The catalog was made homogeneous in magnitude in order to avoid the differences in the way this parameter is reported by various agencies. Instead of using a linear regression to converts from m b and M d to M s or M w , using only events for which estimates of both magnitudes are available (i.e., paired data), we used the frequency-magnitude relations relying on the a and b values of the Gutenberg-Richter relation. The seismic regions are divided into three main categories: seismicity associated with the subduction process along the Pacific coast of Mexico, in-slab events within the down-going COC and RIV plates, and crustal seismicity associated to various geologic and tectonic regions. In total, 18 seismic regions were identified and delimited. For each, the a and b values of the Gutenberg-Richter relation were determined using a maximum likelihood estimation. The a and b parameters were repeatedly estimated as a function of time for each region, in order to confirm their reliability and stability. The recurrence times predicted by the resulting Gutenberg-Richter relations obtained are compared with the observed recurrence times of the larger events in each region of both historical and instrumental earthquakes. 相似文献
20.
A. Ya. Sidorin 《Seismic Instruments》2010,46(3):237-249
The catalog of earthquakes that happened in Greece over the period of 1964 to 2008 was used for the analysis of their diurnal periodicity in this region. The quality of the catalog was examined with the defining of the representativeness levels of earthquakes in different selections. The earthquakes, including relatively strong events with the magnitude M ≥ 4.0, demonstrate diurnal periodicity with seasonal differences in their course reflected in their higher summer seismicity as compared with the winter one. 相似文献