The depth variations in the b-value of frequency-magnitude distribution of the earthquakes in the Garm region of Tajikistan

2014 ◽  
Vol 50 (2) ◽  
pp. 273-288 ◽  
Author(s):  
G. A. Popandopoulos ◽  
A. A. Lukk
Keyword(s):  
B Value ◽  
Magnitude Distribution ◽  
Frequency Magnitude Distribution ◽  
Frequency Magnitude

Mapping b-Value Anomalies Along the Indonesian Island Chain: Implications for Upcoming Earthquakes

2014 ◽  
Vol 08 (04) ◽  
pp. 1450010 ◽  
Author(s):  
Santi Pailoplee
Keyword(s):  
Spatial Relationship ◽  
B Value ◽  
Fixed Number ◽  
Earthquake Catalogue ◽  
Suitable Assumption ◽  
B Values ◽  
Magnitude Distribution ◽  
Risk Areas ◽  
Frequency Magnitude Distribution ◽  
Frequency Magnitude

In this study, the geospatial frequency–magnitude distribution (FMD) b-value images of the prospect sources of upcoming earthquakes were investigated along the Indonesian Sunda Margin (ISM) that strikes parallel to and near the Indonesian Island chain. After enhancing the completeness and stability of the earthquake catalogue, the seismicity data were separated according to their seismotectonic setting into shallow crustal and Intraslab earthquakes. In order to verify the spatial relationship between the b-values and the occurrence of subsequent major earthquakes, the complete shallow crustal seismicity dataset (1980–2005) was truncated into the 1980–2000 sub-dataset. Utilizing the suitable assumption of fixed-number of earthquakes, retrospective tests of both the complete and truncated datasets supported that areas of comparatively low b-values could reasonably be expected to predict likely hypocenters of future earthquakes. As a result, the present-day distributions of b-values derived from the complete (1980–2005) shallow crustal and Intraslab seismicity datasets revealed eight and six earthquake-prone areas, respectively, along the ISM. Since most of these high risk areas proposed here are quite close to the major cities of Indonesia, attention should be paid and mitigation plans should be developed for both seismic and tsunami hazards.

A grid-based b-value approximation through Southern and Northern Norway: preliminary results 

2021 ◽  
Author(s):  
Rodrigo Estay ◽  
Claudia Pavez
Keyword(s):  
B Value ◽  
Seismic Events ◽  
Online Database ◽  
Magnitude Of Completeness ◽  
Stress Regime ◽  
Magnitude Distribution ◽  
The Mean ◽  
Frequency Magnitude Distribution ◽  
Frequency Magnitude ◽  
Grid Based

<p>The Gutenberg – Richter’s b-value is commonly used to analyze the frequency-magnitude distribution of earthquakes, describing the proportion of small and large seismic events as the first estimation of seismic hazard. Additionally, the b-value has been used as a stress meter, giving some insights into the stress regime in different regions around the world. In this research, a grid-based spatial distribution for the b – value was estimated in three different areas of Norway: northern (74°-81° N/ 12°-26° E), southern (57°-64°N/3°-12° E), and the ridge zones of Mohns and Knipovich. For this, we used a complete catalog from the years 2000 to 2019, which was obtained from the Norwegian National Seismic Network online database. The magnitude of completeness was estimated separately for each zone both in time and space, covering a total area of ~425,000 km<sup>2</sup>. Our results show a regional variation of the mean b-value for northern (b<sub>north</sub> = 0.79) and southern (b<sub>south</sub> = 1.03) Norway, and the Ridge (b<sub>ridge</sub> = 0.73), which can be interpreted in terms of the predominant stress regime in the different zones. So far, a few calculations regarding the b-value were previously done in Norway to analyze local intraplate sequences. Then, according to our knowledge, this research corresponds to the first estimation of a regional spatial variation of the b – value in the country.</p>

scholarly journals The Effect of Declustering on the Size Distribution of Mainshocks

2021 ◽  
Author(s):  
Leila Mizrahi ◽  
Shyam Nandan ◽  
Stefan Wiemer
Keyword(s):  
Seismic Hazard Assessment ◽  
B Value ◽  
Aftershock Sequence ◽  
Earthquake Catalogs ◽  
Magnitude Distribution ◽  
Independent Events ◽  
Potential Source ◽  
Epidemic Type Aftershock Sequence ◽  
Frequency Magnitude Distribution ◽  
Frequency Magnitude

Abstract Declustering aims to divide earthquake catalogs into independent events (mainshocks), and dependent (clustered) events, and is an integral component of many seismicity studies, including seismic hazard assessment. We assess the effect of declustering on the frequency–magnitude distribution of mainshocks. In particular, we examine the dependence of the b-value of declustered catalogs on the choice of declustering approach and algorithm-specific parameters. Using the catalog of earthquakes in California since 1980, we show that the b-value decreases by up to 30% due to declustering with respect to the undeclustered catalog. The extent of the reduction is highly dependent on the declustering method and parameters applied. We then reproduce a similar effect by declustering synthetic earthquake catalogs with known b-value, which have been generated using an epidemic-type aftershock sequence model. Our analysis suggests that the observed decrease in b-value must, at least partially, arise from the application of the declustering algorithm on the catalog, rather than from differences in the nature of mainshocks versus fore- or aftershocks. We conclude that declustering should be considered as a potential source of bias in seismicity and hazard studies.

B-Value Analysis of AE Signal Subjected to Stepwise Loading

2011 ◽  
Vol 403-408 ◽  
pp. 4126-4131 ◽  
Author(s):  
Noorsuhada Md Nor ◽  
Norazura Muhamad Bunnori ◽  
Ibrahim Azmi ◽  
Shahidan Shahiron ◽  
Siti Ramziah Basri ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
B Value ◽  
Assessment Method ◽  
Value Analysis ◽  
Magnitude Distribution ◽  
Ae Signal ◽  
Linear Slope ◽  
Log Linear ◽  
Frequency Magnitude Distribution ◽  
Frequency Magnitude

Acoustic emission is an effective damage assessment method in a structure subjected to mechanical loading. Calculation of log-linear slope of the frequency-magnitude distribution of acoustic emission (known as b-value) has been carried out. It is found that the b-valuefor the log frequency-magnitude graph has a good correlation for beam imposed of stepwise loading.It also can be seen that the b-value is decreased as the load increased.

b-VALUE ANOMALIES ALONG THE NORTHERN SEGMENT OF THE SUMATRA–ANDAMAN SUBDUCTION ZONE: IMPLICATIONS FOR UPCOMING EARTHQUAKES

2013 ◽  
Vol 07 (04) ◽  
pp. 1350030 ◽  
Author(s):  
SANTI PAILOPLEE ◽  
PEERASIT SURAKIATCHAI ◽  
PUNYA CHARUSIRI
Keyword(s):  
Subduction Zone ◽  
B Value ◽  
Earthquake Catalogue ◽  
B Values ◽  
Magnitude Distribution ◽  
Nicobar Islands ◽  
Spatial Investigation ◽  
Frequency Magnitude Distribution ◽  
Northern Segment ◽  
Frequency Magnitude

The potential areas of upcoming earthquakes were investigated along the Northern segment of the Sumatra–Andaman Subduction Zone according to the b-value of the frequency-magnitude distribution. After enhancing the completeness of the earthquake catalogue, two datasets, those recorded during (i) 1980–1994 and (ii) 1980–2003, were tested in order to verify the effective correlation between precursory b-values and the location of subsequent earthquakes. The results confirmed that areas with low b-values agreed well with the locations of the subsequent earthquakes in that region. Accordingly, the present-day dataset from 1980–2010 was carefully evaluated to determine the b-values across the region. Within this spatial investigation, three areas of low b-values and so potential hazards were found. These consisted of the (i) West coast of Myanmar, and (ii) North and (iii) South of the Nicobar Islands. From 2010–2012, a major earthquake with magnitude 7.5 mb was recorded as being generated in the region South of the Nicobar Islands. Thus, attention should be paid to the remaining two until now quiescent areas, and mitigation plans should be raised for both seismic and tsunami hazards.

The relationship between ML and Mw for small earthquakes (ML < 2-4) in Italy

2020 ◽  
Author(s):  
Barbara Lolli ◽  
Gasperini Paolo ◽  
Emanuele Biondini ◽  
Gianfranco Vannucci
Keyword(s):  
Wave Attenuation ◽  
General Characteristic ◽  
B Value ◽  
Corner Frequency ◽  
Magnitude Distribution ◽  
Linear Behavior ◽  
Frequency Magnitude Distribution ◽  
The Relationship ◽  
Theoretical Considerations ◽  
Frequency Magnitude

&lt;p&gt;Several authors empirically observed that the scaling between local magnitude ML and moment magnitude Mw computed by spectral methods is not 1:1 for ML&lt;2-4. In particular ML is found to be about proportional to 1.5 Mw but the exact threshold below which this occurs is argued. Such behavior was explained as due to attenuation and scattering along the path or to a minimum limit in the pulse duration or equivalently a maximum limit to the corner frequency of the observed spectra imposed by surface attenuation. The frequency-magnitude distribution of ML estimates provided by the Italian Seismic Instrumental Database (ISIDe) of INGV show a strictly linear behavior with b-value&amp;#187;1.0 down to about ML 1.4 at least. This implies that for Mw the b-value would be about 1.5 below magnitude 2-4 and 1 above. As the frequency magnitude relationship with b-value&amp;#187;1 in terms of Mw is recognized as a general characteristic of seismicity all over the world, based on both empirical and theoretical considerations, the question arises on the reasons of the observed discrepancy for small shocks. One explanation might be the assumption of incorrect seismic wave attenuation properties for the computation of ML, of spectral Mw or both.&lt;/p&gt;

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