SOURCE PARAMETER AND B-VALUE ESTIMATION OF LOCAL EARTHQUAKES IN KUMAUN REGION, CENTRAL HIMALAYA, INDIA.

SUMMARY An unbiased estimation of the b-value and of its variability is essential to verify empirically its physical contribution to the earthquake generation process, and the capability to improve earthquake forecasting and seismic hazard. Notwithstanding the vast literature on the b-value estimation, we note that some potential sources of bias that may lead to non-physical b-value variations are too often ignored in seismological common practice. The aim of this paper is to discuss some of them in detail, when the b-value is estimated through the popular Aki’s formula. Specifically, we describe how a finite data set can lead to biased evaluations of the b-value and its uncertainty, which are caused by the correlation between the b-value and the maximum magnitude of the data set; we quantify analytically the bias on the b-value caused by the magnitude binning; we show how departures from the exponential distribution of the magnitude, caused by a truncated Gutenberg–Richter law and by catalogue incompleteness, can affect the b-value estimation and the search for statistically significant variations; we derive explicitly the statistical distribution of the magnitude affected by random symmetrical error, showing that the magnitude error does not induce any further significant bias, at least for reasonable amplitude of the measurement error. Finally, we provide some recipes to minimize the impact of these potential sources of bias.

Download Full-text

Proper b-value Estimation Method in Rock Acoustic Emission Testing

10.1002/essoar.10502459.1 ◽

2020 ◽

Author(s):

Xiling Liu ◽

MengSi Han ◽

Wei He ◽

Xibing Li ◽

Daolong Chen

Keyword(s):

Acoustic Emission ◽

Estimation Method ◽

B Value ◽

Emission Testing ◽

Value Estimation ◽

Acoustic Emission Testing

Download Full-text

Box Counting Fractal Dimension and Frequency Size Distributon of Earthquakes in the Central Himalaya Region

Journal of Institute of Science and Technology ◽

10.3126/jist.v26i2.41664 ◽

2021 ◽

Vol 26 (2) ◽

pp. 127-136

Author(s):

Ram Krishna Tiwari ◽

Harihar Paudyal

Keyword(s):

Fractal Dimension ◽

High Stress ◽

High Strength ◽

B Value ◽

Earthquake Catalog ◽

Central Himalaya ◽

Study Region ◽

B Values ◽

Box Counting ◽

Earthquake Distribution

To establish the relations between b-value and fractal dimension (D0) for the earthquake distribution, we study the regional variations of those parameters in the central Himalaya region. The earthquake catalog of 989 events (Mc = 4.0) from 1994.01.31 to 2020.10.28 was analyzed in the study. The study region is divided into two sub-regions (I) Region A: 27.3°N -30.3°N and 80°E -84.8°E (western Nepal and vicinity) and (II) Region B: 26.4°N -28.6°N and 84.8°E -88.4°E (eastern Nepal and vicinity). The b-value observed is within the range between 0.92 to 1.02 for region A and 0.64 to 0.74 for region B showing the homogeneous nature of the variation. The seismic a-value for those regions ranges respectively between 5.385 to 6.007 and 4.565 to 5.218. The low b-values and low seismicity noted for region B may be related with less heterogeneity and high strength in the crust. The high seismicity with average b-values obtained for region A may be related with high heterogeneity and low strength in the crust. The fractal dimension ≥1.74 for region A and ≥ 1.82 for region B indicate that the earthquakes were distributed over two-dimensional embedding space. The observed correlation between D0 and b is negative for western Nepal and positive for eastern Nepal while the correlation between D0 and a/b value is just opposite for the respective regions. The findings identify both regions as high-stress regions. The results coming from the study agree with the results of the preceding works and reveal information about the local disparity of stress and change in tectonic complexity in the central Himalaya region.

Download Full-text

Uncertainty Of B-Value Estimation In Connection With Magnitude Distribution Properties Of Small Data Sets

Seventh EAGE Workshop on Passive Seismic 2018 ◽

10.3997/2214-4609.201800052 ◽

2017 ◽

Author(s):

K. Leptokaropoulos ◽

A. Adamaki

Keyword(s):

B Value ◽

Small Data ◽

Data Sets ◽

Magnitude Distribution ◽

Value Estimation ◽

Small Data Sets

Download Full-text

Changes in local B-value prior to moderate local earthquakes: Gulf of Aqabah, northern red sea

International Journal of the Physical Sciences ◽

10.5897/ijps11.979 ◽

2011 ◽

Vol 6 (36) ◽

Author(s):

Nassir S. Al-Arifi

Keyword(s):

Red Sea ◽

B Value ◽

Local Earthquakes ◽

Northern Red Sea

Download Full-text

Statistics of the earthquakes in the central Himalaya and its vicinity in last 56 years, with an emphasis in the 25 April 2015 Gorkha, Nepal earthquake

Contributions to Geophysics and Geodesy ◽

10.31577/congeo.2021.51.4.2 ◽

2021 ◽

Vol 51 (4) ◽

pp. 321-343

Author(s):

Ram Krishna TIWARI ◽

Harihar PAUDYAL

Keyword(s):

Fractal Dimension ◽

Statistical Analysis ◽

High Stress ◽

Large Earthquake ◽

B Value ◽

Earthquake Activity ◽

Central Himalaya ◽

Magnitude Distribution ◽

Average Value ◽

Central Nepal

To understand the variation of stress levels in the region 80°E – 89°E and 26°N – 31°N, the statistical analysis of earthquake frequency-magnitude distribution and spatio-temporal variation of fractal correlation dimension of earthquake epicenter distribution are estimated. The analysis is carried out on declusterised catalogue containing 1185 events of 56 years from February 1964 to November 2020. The study area is divided into three regions the western Nepal and vicinity (Region A), central Nepal and vicinity (Region B) and eastern Nepal and vicinity (Region C), respectively. The magnitude of completeness (Mc) varies from 3.6 to 4.0 for the study period. The spatial fractal dimension (Dc) and b-value are calculated as 1.89 ± 0.02 and 0.68 ± 0.03 for the western Nepal, 1.76 ± 0.01 and 0.60 ± 0.05 for the central Nepal, whereas they are estimated as 1.85 ± 0.02 and 0.63 ± 0.03 for the eastern part of the Nepal. The b-values obtained for all three regions are very low comparing to global average value of 1. The time clustering of the events in the respective regions are 0.26 ± 0.003, 0.31 ± 0.004 and 0.26 ± 0.02 as indicated by temporal fractal dimension (Dt). The higher Dc, lower b and Dt values associated with the regions indicate high stress concentration and stronger epicenter clustering in these regions. The strongly increasing trend of fractal dimension and strongly decreasing trend of b-value show the high probabilities of occurring the large earthquake in both central Nepal (82.5°E – 85.5°E and 27.5°N – 30°N) and eastern Nepal (85.5°E – 88.2°E and 26.45°N – 28.6°N) as compared to western Nepal (80°E – 82.5°E and 28°N – 30.5°N). This statistical analysis of spatial and temporal characteristics of the earthquake activity may give significant signs of the future seismic hazard along central Himalaya region.

Download Full-text