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Frontiers of Earth Science 2018年第1期12卷 215-236页

作者： S. OZTURK Gumushane University Department of Geophysics TR-29100 Gumushane Turkey

The Eastern Anatolian Region of Turkey is one of the most seismically and tectonically active regions due to the frequent occurrence of earthquakes. Thus, the main goal of this study is to analyze the regional and temporal characteristics of seismicity in the Eastern Anatolia in terms of the seismotectonic b-value, fractal dimension Dcvalue, precursory seismic quiescence Z-value, and their interrelationships. This study also seeks to obtain a reliable empirical relation between b and De-values and to evaluate the temporal changes of these parameters as they relate to the earthquake potential of the region. A more up-to-date relation of De = 2.55 -0.39＊b is found with a very strong negative correlation coefficient （r=- 0.95） by using the orthogonal regression method. The b-values less than 1.0 and the De-values greater than 2.2 are observed in the Northeast Anatolian Fault Zone, Askale, Erzurum, Igdlr and Caldlran Faults, Dogubeyazlt Fault Zone, around the Genc Fault, the western part of the bitlis-Zagros Thrust Zone, Pulumir and Karakogan Faults, and the SancakUzunpmar Fault Zone. In addition, the regions having small b-values and large Z-values are calculated around the Geng, Piulumur and Karakogan Faults as well as the Saneak-Uzunpmar Fault Zone. Remarkably, the combinations of these seismotectonic parameters could reveal the earthquake hazard potential in the Eastern Anatolian Region of Turkey, thus creating an increased interest in these anomaly regions.

关键词： Eastern Anatolia b-value fractal dimension,precursory seismic quiescence earthquake hazard

Correcting the Gutenberg–Richter b-value for effects of rounding and noise

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Earthquake Science 2015年第2期28卷 129-134页

作者： V.H.Márquez-Ramírez F.A.Nava F.R.Zúiga UNAM Campus Querétaro México Centro de GeocienciasBlvd.Juriquilla No 3001 76230 México Querétaro México Seismology Department CICESE Carretera Ensenada-Tijuana No 3918 Zona Playitas 22860 Ensenada BC México

The effects of magnitude rounding and of the presence of noise in the rounded magnitudes on the estimation of the Gutenberg-Richter b-value are explored, and the ways to correct for these effects are proposed. For typical values, b = 1 and rounding interval △M = 0.1, the rounding error is approximately -10^-3 and it can be corrected to a negligible approximately -10^-5. For the same typical values, the effect of noise can be larger, depending on the characteristics of the noise distribution; for normally distributed noise with standard deviation σ = 0.1, the correct b-value may be underestimated by a factor - 0.97.

关键词： b-value Noise Magnitude

The effect of the magnitude uncertainty on the b value

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Acta Seismologica Sinica(English Edition) 2000年第4期13卷 359-367页

作者：秦长源 Laboratory of Geophysics University of Thessaloniki Thessaloniki Greece

Since the magnitude is usually not the same from one catalog to another for the same earthquake, the calculated b value will change with different catalogs. big b error is usually introduced when the magnitudes of the events are not well measured. For this reason, based on the uncertainty of the observed magnitude, i.e., the 'apparent' magnitude, the frequency-magnitude relation (Gutenberg-Richter relation) was estimated by assuming the normal distribution of the apparent magnitude around the 'true' one. The number of the events with same 'true' magnitude was recalculated according to this distribution. The error of the b value obtained with the 'true' magnitude is largely reduced by taking into account the distribution of the 'apparent' one. In order to show the advantage of the present method, the b values in the three zones in China are calculated with both ordinary and present method. Furthermore, in consideration of the magnitude saturation of the large events, the data set was divided into two pats on M=7.0. Results obtained by the method presented in this paper are of higher precision than those with ordinary method.

关键词： magnitude uncertainty b-value

Joint analysis of b-value and apparent stress before the 2011 M_(W)9.0 Tohoku-Oki, Japan earthquake

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Earthquake Science 2021年第4期34卷 323-333页

作者： Yane Li Xuezhong Chen Lijuan Chen Institute of Geophysics China Earthquake AdministrationBeijing 100081China Chongqing Earthquake Agency Chongqing 401147China

Detecting tempo-spatial changes of crust stress associated with major earthquakes has implications for understanding earthquake seismogenic processes.We conducted a joint analysis of b-value and apparent stress in the source region before the March 11,2011 MW9.0 TohokuOki,Japan earthquake.Earthquakes that occurred between January 1,2000 and March 8,2011 were used to estimate bvalues,while source parameters of events with magnitudes of Ms5.0–6.9 between January 1,1997 and March 8,2011 were used to calculate the apparent stresses.Our results show that the average b-value decreased steadily from 1.26 in 2003 to 0.99 before the Tohoku-Oki mainshock.This b-value decrease coincided with an increase in the apparent stress from 0.65 MPa to 1.64 MPa.Our results reveal a clear negative correlation between the decrease in b-value and increase in apparent stress,which lasted for approximately eight years prior to the 2011 mainshock.Additionally,spatial pattern results of the relative change in b-value show that the area associated with drastic b-value decreases(25%or greater)was concentrated near the 2011 mainshock epicenter.The joint analysis of b-value and apparent stress provides a promising method for detecting anomalies that could serve as potential indicators of large earthquakes.

关键词： 2011 Tohoku-Oki earthquake b-value apparent stress time variation.

Continuous-cyclic variations in the b-value of the earthquake frequency-magnitude distribution

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Earthquake Science 2013年第5期26卷 301-320页

作者： Z.H.El-Isa Geology Department University of Jordan

Seismicity of the Earth （M ≥ 4.5） was compiled from NEIC, IRIS and ISC catalogues and used to compute b-value based on various time windows. It is found that continuous cyclic b-variations occur on both long and short time scales, the latter being of much higher value and sometimes in excess of 0.7 of the absolute b-value. These variations occur not only yearly or monthly, but also daily. before the occurrence of large earthquakes, b-values start increasing with variable gradients that are affected by foreshocks. In some cases, the gradient is reduced to zero or to a negative value a few days before the earthquake occurrence. In general, calculated b-values attain maxima 1 day before large earthquakes and minima soon after their occurrence. both linear regression and maximum likelihood methods give correlatable, but variable results. It is found that an expanding time window technique from a fixed starting point is more effective in the study of b-variations. The calculated b-variations for the whole Earth, its hemispheres, quadrants and the epicentral regions of some large earthquakes are of both local and regional character, which may indicate that in such cases, the geodynamic processes acting within a certain region have a much regional effect within the Earth. The b-variations have long been known to vary with a number of local and regional factors including tectonic stresses. The results reported here indicate that geotectonic stress remains the most significant factor that controls b-variations. It is found that for earthquakes with Mw ≥ 7, an increase of about 0.20 in the b-value implies a stress increase that will result in an earthquake with a magnitude one unit higher.

关键词： Earthquake frequency-magnitude b-value Temporal b-variation Spatial b-variation

The spatiotemporal variation of the b-value and its tectonic implications in North China

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Earthquake Science 2014年第3期27卷 301-310页

作者： Yujie Zheng Shiyong Zhou School of Earth and Space Sciences Peking University

In this study, we adopt an improved bayesian approach based on free-knot b-spline bases to study the spatial and temporal distribution of the b-value. Synthetic tests show that the improved bayesian approach has a superior performance compared to the bayesian approach as well as the widely used maximum likelihood estimation （MLE） method in fitting the real variation of b-values. We then apply the improved bayesian approach to North China and find that the b-value has a clear relevance to seismicity. Temporal changes of b-values are also investigated in two specific areas of North China. We interpret sharp decreases in the b-values as useful messages in earthquake hazard analysis.

关键词： Improved bayesian approach b-splines b-value Frequency-magnitude distribution North China Earthquake hazard analysis

The b-value and fractal dimension of local seismicity around Koyna Dam(India)

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Earthquake Science 2013年第2期26卷 99-105页

作者： Arjun Kumar S.S.Rai Anand Joshi Himanshu Mittal Rajiv Sachdeva Rohtash Kumar Vandana Ghangas IIT Roorkee Roorkee247667UttarakhandIndia National Geophysical Research Institute

Earthquakes began to occur in Koyna region （India） soon after the filling of Koyna Dam in 1962. In the present study, three datasets 1964-1993, 1993-1995, and 1996-1997 are analyzed to study the b-value and fractal dimension. The b-value is calculated using the Gutenberg- Richter relationship and fractal dimension Dcorr. using correlation integral method. The estimated b-value and Dcorr. of this region before 1993 are found to be in good agreement with previously reported studies. In the sub- sequent years after 1995, the b-value shows an increase. The estimated b-values of this region are found within the limits of global average. Also, the pattern of spatial clustering of earthquakes show increase in clustering and migration along the three zones called North-East Zone, South-East Zone （SEZ）, and Warna Seismic Zone. The earthquake events having depth ≤5 km are largely confined to SEZ. After 1993, the Dcorr. shows decrease, implying that earth- quake activity gets clustered. This seismic clustering could be helpful for earthquake forecasting.

关键词： Koyna Fractals b-value Correlationdimension Algorithm

Some Statistical Aspects for Algerian Earthquake Catalogue

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Journal of Civil Engineering and Architecture 2024年第5期18卷 236-243页

作者： Fouzi bellalem Department of Seismological Survey CRAAG(Center of Research in AstronomyAstrophysicsand Geophysics)Bouzareah 16340Algeria

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.

关键词： Seismic activity b-value z-value change magnitude of completeness Algeria

b-value and fractal dimension variations in Iran

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Earthquake Science 2019年第2期32卷 57-63页

作者： Alireza Firoozfar bahman Ansari Department of Civil Engineering University of ZanjanZanjan38791-45371Iran

Iran sits on a region with a high intrinsic level of seismic activity due to its tectonic setting.Through statistical examination of the earthquakes listed in the catalogue from International Institute of Earthquake Engineering and Seismology(IIEES),this research attempted to calculate some seismicity factors and find correlation between them.A preliminary analysis indicated changes in theb-value of the Gutenberg-Richter relationship over the study region.Thus,the study area was divided into five zones(Alborz,Zagros,Azerbaijan,Central and East)andb-value was computed for each zone.Considering faulting mechanism styles and theb-values in the region,it was found that the lowestb-values belong to the thrust events and strike-slip faulting earthquakes have intermediate values.These findings support previous studies.Furthermore,results ofb-value calculation were used for the estimation of accumulated differential stresses(σ1–σ2)over each zone.Overall,theb-value for Iran is averagely low which signifies the high stress tectonic regime in this region.Also,by having calculated fractal dimension(D)in each zone,a correlation obtained showing that in Iran region,theb-value correlates to fractal dimension byD=4.2b–2 relation which does not support Aki's(1981)speculation ofD=3b/c.

关键词： stress faulting style Iran plateau b-value fractal di-mension

Self-Organized Fractal Seismicity and b-value of Aftershocks of the 2015 Gorkha Earthquake, Nepal

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International Journal of Geosciences 2020年第8期11卷 562-579页

作者： Sanchit Minocha Imtiyaz A. Parvez Indian Institute of Technology Roorkee (IITR) Roorkee India CSIR Fourth Paradigm Institute (Formerly CSIR C-MMACS) Bangalore India

The Gorkha Earthquake that occurred on 25th April 2015 was a long anticipated, low angle thrust-faulting shallow event in Central Nepal that devastated the mountainous southern rim of the High Himalayan range. The earthquake was felt throughout central and eastern Nepal, much of the Ganges River plain in northern India, and northwestern bangladesh, as well as in the southern parts of the Plateau of Tibet and western bhutan. Two large aftershocks, with magnitudes 6.6 and 6.7, occurred in the region within one day of the main event, and several dozen smaller aftershocks occurred in the region during the succeeding days. In this study, we have analyzed the 350 aftershocks of the 2015 Gorkha Earthquake of Mb>wb> 7.8 to understand the spatial and temporal distribution of b-value and the fractal correlation dimension. The b-value is found to be 0.833 ± 0.035 from the Gutenberg-Richter relation by the least squares method and 0.95 ± 0.05 by the maximum likelihood method, indicating high stress bearing source zone. The spatial and temporal correlation dimension is estimated to be 1.07 ± 0.028 and 0.395 ± 0.0027 respectively. Spatial correlation dimension suggests a heterogeneous distribution of earthquake epicenters over a linear structure in space, while the temporal correlation dimension suggests clustering of aftershock activity in the time domain. The spatial variation of the b-value reveals that the b-value is high in the vicinity of the mainshock which is due to the sudden release of stress energy in the form of seismic waves. The spatial distribution of correlation dimension further confirms a linear source in the source zone as it varies from 0.8-1.0 in most of the region. We have also studied the temporal variation of b-value and correlation dimension that shows positive correlation for about first 15 days, then a negative correlation for next 45 days and after that, a positive correlation. The positive correlation suggests that the probability of large magnitude earthquakes decreases in respon

关键词： Nepal Earthquake Gorkha Earthquake b-value Fractal Dimension