scholarly journals Spatiotemporal heterogeneity of <i>b</i> values revealed by a data-driven approach for the 17 June 2019 <i>M</i><sub>S</sub> 6.0 Changning earthquake sequence, Sichuan, China

2021 ◽  
Vol 21 (7) ◽  
pp. 2233-2244
Author(s):  
Changsheng Jiang ◽  
Libo Han ◽  
Feng Long ◽  
Guijuan Lai ◽  
Fengling Yin ◽  
...  
Keyword(s):  
Source Region ◽  
Parametric Method ◽  
Information Criterion ◽  
B Value ◽  
Aftershock Sequence ◽  
Data Driven ◽  
Earthquake Hazards ◽  
Absolute Deviation ◽  
B Values ◽  
Spatiotemporal Heterogeneity

Abstract. The spatiotemporal heterogeneity of b values has great potential for helping in understanding the seismogenic process and assessing seismic hazard. However, there is still much controversy about whether it exists or not, and an important reason is that the choice of subjective parameters has eroded the foundations of much research. To overcome this problem, we used a recently developed non-parametric method based on a data-driven concept to calculate b values. The major steps of this method include (1) performing a large number of Voronoi tessellations and Bayesian information criterion (BIC) value calculation, selecting the optimal models for the study area, and (2) using the ensemble median (Q2) and median absolute deviation (MAD) value to represent the final b value and its uncertainty. We investigated spatiotemporal variations in b values before and after the 2019 Changning MS=6.0 earthquake in the Sichuan Basin, China. The results reveal a spatial volume with low pre-mainshock b values near the mainshock source region, and its size corresponds roughly with the rupture area of the mainshock. The anomalously high pre-mainshock b values distributed in the NW direction of the epicenter were interpreted to be related to fluid invasion. The decreases in b values during the aftershock sequence along with the occurrences of several strong aftershocks imply that b values could be an indicator of the stress state. In addition, we found that although the distribution characteristics of b values obtained from different methods of investigation are qualitatively consistent, they differ significantly in terms of their specific values, suggesting that the best way to study the heterogeneous pattern of b values is in the joint dimension of space-time rather than separately in time and space. Overall, our study emphasizes the importance of b-value studies in assessing earthquake hazards.

scholarly journals Spatiotemporal Heterogeneity of <i>b</i> Values Revealed by a Data-Driven Approach for June 17, 2019 <i>M</i><sub>S</sub> 6.0, Changning Sichuan, China earthquake Sequence

2021 ◽  
Author(s):  
Changsheng Jiang ◽  
Libo Han ◽  
Feng Long ◽  
Guijuan Lai ◽  
Fengling Yin ◽  
...  
Keyword(s):  
Voronoi Tessellation ◽  
Source Region ◽  
Parametric Method ◽  
B Value ◽  
Aftershock Sequence ◽  
Data Driven ◽  
Earthquake Hazards ◽  
Absolute Deviation ◽  
B Values ◽  
Spatiotemporal Heterogeneity

Abstract. The spatiotemporal heterogeneity of b values has great potential for understanding the seismogenic process and assessing the seismic hazard. However, there is still much controversy about whether it exists or not, and an important reason is that the choice of subjective parameters has eroded the foundations of many researches. To overcome this problem, we used a recent developed non-parametric method based on the data-driven concept to calculate b values. The major steps of this method include: 1) perform a large number of Voronoi tessellation, Bayesian information criterion (BIC) value calculation and selection of the optimal models for the study area, and 2) use the ensemble median (Q2) and median absolute deviation (MAD) value to represent the final b value and its uncertainty. We investigated spatiotemporal variations of b values before and after the 2019 Changning MS 6.0 earthquake in Sichuan Basin, China. The results reveal a spatial volume with low pre-mainshock b values near the mainshock source region, and its size corresponds roughly with the rupture area of the mainshock. The anomalously high pre-mainshock b values distributed in the NE direction of the epicenter was interpreted to be related with fluid invasion or increased pore pressure. The decreases of b values during the aftershock sequence along with the occurrences of several strong aftershocks imply that b values could be an indicator of stress state. In addition, we found that although the distribution characteristics of b values obtained from different way of investigating are qualitatively consistent, they differ significantly in terms of their specific values, suggesting that the best way to study the heterogeneous pattern of b values is in the joint dimension of space-time rather than alone in time and space. Overall, our study emphasizes the importance of b value studies on assessing the earthquake hazards.

Two Foreshock Sequences Post Gulia and Wiemer (2019)

2020 ◽  
Vol 91 (5) ◽  
pp. 2843-2850 ◽  
Author(s):  
Kelian Dascher-Cousineau ◽  
Thorne Lay ◽  
Emily E. Brodsky
Keyword(s):  
Puerto Rico ◽  
Real Time ◽  
Exact Result ◽  
Monte Carlo Sampling ◽  
B Value ◽  
Aftershock Sequence ◽  
Traffic Light ◽  
B Values ◽  
Aftershock Sequences ◽  
Abrupt Changes

Abstract Recognizing earthquakes as foreshocks in real time would provide a valuable forecasting capability. In a recent study, Gulia and Wiemer (2019) proposed a traffic-light system that relies on abrupt changes in b-values relative to background values. The approach utilizes high-resolution earthquake catalogs to monitor localized regions around the largest events and distinguish foreshock sequences (reduced b-values) from aftershock sequences (increased b-values). The recent well-recorded earthquake foreshock sequences in Ridgecrest, California, and Maria Antonia, Puerto Rico, provide an opportunity to test the procedure. For Ridgecrest, our b-value time series indicates an elevated risk of a larger impending earthquake during the Mw 6.4 foreshock sequence and provides an ambiguous identification of the onset of the Mw 7.1 aftershock sequence. However, the exact result depends strongly on expert judgment. Monte Carlo sampling across a range of reasonable decisions most often results in ambiguous warning levels. In the case of the Puerto Rico sequence, we record significant drops in b-value prior to and following the largest event (Mw 6.4) in the sequence. The b-value has still not returned to background levels (12 February 2020). The Ridgecrest sequence roughly conforms to expectations; the Puerto Rico sequence will only do so if a larger event occurs in the future with an ensuing b-value increase. Any real-time implementation of this approach will require dense instrumentation, consistent (versioned) low completeness catalogs, well-calibrated maps of regionalized background b-values, systematic real-time catalog production, and robust decision making about the event source volumes to analyze.

The foreshock-aftershock sequence of the March 20 1966 earthquake in the Republic of Congo

1970 ◽  
Vol 60 (4) ◽  
pp. 1245-1258 ◽  
Author(s):  
John Lahr ◽  
Paul W. Pomeroy
Keyword(s):  
Dynamic Range ◽  
B Value ◽  
High Gain ◽  
Aftershock Sequence ◽  
Confidence Limits ◽  
B Values ◽  
Aftershock Sequences ◽  
Successful Prediction ◽  
Seismograph Station ◽  
The Republic

abstract The activity associated with the Congo earthquake of March 20 1966 (mb = 6.5 to 7) was studied with emphasis on the time and magnitude distributions. The data were recorded at the Abéché, Chad, seismograph station operated by Lamont-Doherty Geological Observatory. Over a period of about 70 days, 815 earthquakes with magnitude (mb) greater than or equal to 3.3 were recorded, and they form the basis for this study. The aftershocks are distributed with magnitude (mb) according to the formula long n = a - bm with b = 1.05 ± 0.07 at the 95 per cent confidence limits. The foreshocks have b = 1.06 ± 0.35 at the 95 per cent confidence limits. These b values are in general agreement with b values derived from other aftershock sequences throughout the world. Some authors have suggested that foreshocks may have a lower b value than background activity and that this difference might be used in earthquake prediction. In this paper, an evaluation is made of the limitations of this method of prediction. Assuming that such a difference in b values does exist, it is found that a closely spaced network of high-gain seismographs with wide dynamic range would be required to assure successful prediction.

scholarly journals Statistical analysis of aftershock sequences related with two major Nepal earthquakes: April 25, 2015, MW 7.8, and May 12, 2015, MW 7.2

2016 ◽  
Vol 59 (5) ◽  
Author(s):  
Prasanta Chingtham ◽  
Babita Sharma ◽  
Sumer Chopra ◽  
Pareshnath SinghaRoy
Keyword(s):  
Scaling Laws ◽  
Main Shock ◽  
B Value ◽  
Temporal Variations ◽  
Aftershock Sequence ◽  
Earthquake Catalog ◽  
Study Region ◽  
Nepal Himalaya ◽  
B Values ◽  
Aftershock Sequences

Present study describes the statistical properties of aftershock sequences related with two major Nepal earthquakes (April 25, 2015, MW 7.8, and May 12, 2015, MW 7.2) and their correlations with the tectonics of Nepal Himalaya. The established empirical scaling laws such as the Gutenberg–Richter (GR) relation, the modified Omori law, and the fractal dimension for both the aftershock sequences of Nepal earthquakes have been investigated to assess the spatio-temporal characteristics of these sequences. For this purpose, the homogenized earthquake catalog in moment magnitude, MW is compiled from International Seismological Center (ISC) and Global Centroid Moment Tensor (GCMT) databases during the period from April 25 to October 31, 2015. The magnitude of completeness, MC, a and b-values of Gutenberg–Richter relationship for the first aftershock sequence are found to be 3.0, 4.74, 0.75 (±0.03) respectively whereas the MC, a and b-values of the same relationship for the second aftershock sequence are calculated to be 3.3, 5.46, 0.90 (±0.04) respectively. The observed low b-values for both the sequences, as compared to the global mean of 1.0 indicate the presence of high differential stress accumulations within the fractured rock mass of Nepal Himalaya. The calculated p-values of 1.01 ± 0.05 and 0.95 ± 0.04 respectively for both the aftershock sequences also imply that the aftershock sequence of first main-shock exhibits relatively faster temporal decay pattern than the aftershock sequence of second main-shock. The fractal dimensions, DC values of 1.84 ± 0.05 and 1.91 ± 0.05 respectively for both the aftershock sequences of Nepal earthquakes also reveal the clustering pattern of earthquakes and signifies that the aftershocks are scattered all around the two dimensional space of fractured fault systems of the Nepal region. The low b-value and low DC observed in the temporal variations of b-value and DC before the investigated earthquake (MW 7.2) suggest the presence of high-stress concentrations in the thrusting regimes of the Nepal region before the failure of faults. Moreover, the decrease of b-value with the corresponding decrease of DC observed in their temporal variations can primarily act as an indicator for possible prediction of major earthquakes in the study region.

scholarly journals Spatial and Temporal Variations of Gutenberg-Richter b-Values Using Classic Method of Moment (CMM) and Seismicity in and Around Van Lake

2019 ◽  
Vol 2 (2) ◽  
pp. 192-199
Author(s):  
Tuğba Türker ◽  
Yusuf Bayrak
Keyword(s):  
Source Region ◽  
Earthquake Hazard ◽  
Seismic Source ◽  
B Value ◽  
Temporal Variations ◽  
Lake Van ◽  
Method Of Moment ◽  
B Values ◽  
Classic Method ◽  
Gis System

The aim of this study determined spatial-temporal variations of Gutenberg-Richter b-values using the Classic Method of Moment (CMM) and seismicity in and around Lake Van. We wrote a Matlab program for this method in the Matlab system. The faults for the Van region used as updated in the GIS system given the reference from the different sources by Bayrak and Türker (will be used in the doctoral thesis). Around Lake Van divided into 4 different seismic source regions. For each seismic source region, probabilities ranging from 0 to 1, the annual probability of exceedances and return periods were calculated for the next 25, 50 and 100 years. Van region determined the seismicity b value changes, β-values. We mapped spatial variations of the b-values using the GIS system. As a result, Lake Van region (region 2) occurred 7.1 magnitude an earthquake in the next 100 years with 31 % probability levels. If it occurred in the 50 years with 15 % probability levels, in the 25 years with 7.8 % probability levels. We estimated the low b-values in the Lake Van so, it has been the high seismicity and can be occurred an earthquake as the high magnitude in the next years. This study will be lead to earthquake hazard analysis and seismic hazard studies in and around Lake Van.

Earthquake migration in the Fairbanks, Alaska seismic zone

1980 ◽  
Vol 70 (1) ◽  
pp. 223-241
Author(s):  
Larry Gedney ◽  
Steve Estes ◽  
Nirendra Biswas
Keyword(s):  
B Value ◽  
Aftershock Sequence ◽  
Stress Axis ◽  
Seismic Zone ◽  
Epicentral Area ◽  
Focal Mechanism Solutions ◽  
Relative Stress ◽  
Earthquake Migration ◽  
Dislocation Process ◽  
High Level

abstract Since a series of moderate earthquakes near Fairbanks, Alaska in 1967, the “Fairbanks seismic zone” has maintained a consistently high level of seismicity interspersed with sporadic earthquake swarms. Five swarms occurring since 1970 demonstrate that tightly compacted centers of activity have tended to migrate away from the epicentral area of the 1967 earthquakes. Comparative b-coefficients of the first four swarms indicate that they occurred under different relative stress conditions than the last episode, which exhibited a higher b-value and was, in fact, a main shock of magnitude 4.6 with a rapidly decaying aftershock sequence. This last recorded sequence in February 1979 was an extension to greater depths along a lineal seismic zone whose first recorded activation occurred during a swarm two years earlier. Focal mechanism solutions indicate a north-south orientation of the greatest principal stress axis, σ1, in the area. A dislocation process related to crustal spreading between strands of a right-lateral fault, similar to that which has been inferred for southern California, is suggested.

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

Observations of the Coyote Lake, California earthquake sequence of August 6, 1979

1980 ◽  
Vol 70 (2) ◽  
pp. 559-570 ◽  
Author(s):  
R. A. Uhrhammer
Keyword(s):  
San Francisco ◽  
Fault Zone ◽  
Strong Earthquake ◽  
Main Shock ◽  
B Value ◽  
Aftershock Sequence ◽  
The South ◽  
The North ◽  
Temporal And Spatial Characteristics ◽  
Largest Aftershock

abstract At 1705 UTC on August 6, 1979, a strong earthquake (ML = 5.9) occurred along the Calaveras fault zone south of Coyote Lake about 110 km southeast of San Francisco. This strong earthquake had an aftershock sequence of 31 events (2.4 ≦ ML ≦ 4.4) during August 1979. No foreshocks (ML ≧ 1.5) were observed in the 3 months prior to the main shock. The local magnitude (ML = 5.9) and the seismic moment (Mo = 6 × 1024 dyne-cm from the SH pulse) for the main shock were determined from the 100 × torsion and 3-component ultra-long period seismographs located at Berkeley. Local magnitudes are determined for the aftershocks from the maximum trace amplitudes on the Wood-Anderson torsion seismograms recorded at Berkeley (Δ ≊ 110 km). Temporal and spatial characteristics of the aftershock sequence are presented and discussed. Some key observations are: (1) the first six aftershocks (ML ≧ 2.4) proceed along the fault zone progressively to the south of the main shock; (2) all of the aftershocks (ML ≧ 2.4) to the south of the largest aftershock (ML = 4.4) have a different focal mechanism than the aftershocks to the north; (3) no aftershocks (ML ≧ 2.4) were observed significantly to the north of the main shock for the first 5 days of the sequence; and (4) the b-value (0.70 ± 0.17) for the aftershock sequence is not significantly different from the average b-value (0.88 ± 0.08) calculated for the Calaveras fault zone from 16 yr of data.

Earthquake sequences and b values in the southeast United States

1974 ◽  
Vol 64 (1) ◽  
pp. 267-273
Author(s):  
Leland Timothy Long
Keyword(s):  
United States ◽  
South Carolina ◽  
B Value ◽  
Earthquake Activity ◽  
Southeast United States ◽  
B Values ◽  
History Of ◽  
Earthquake Sequences ◽  
Foreshock Activity ◽  
Epicentral Region

abstract Aftershock and foreshock activity within 12 hr of the July 13, 1971 earthquake near Seneca, South Carolina, indicates a b value of 0.9 at ML = 3.0. Approximately 40 events recorded in a 5-day aftershock survey near Seneca indicate a b value of 1.7 at ML = 0.5. A sequence of over 40 events occurring west of McCormick, South Carolina, indicates a b value of 1.3 at ML = 2.4. The McCormick sequence was active for 4 months. Unlike the Seneca region, the McCormick region has a history of earthquake activity. Examinations of other published southeastern b values suggest that southeastern United States earthquakes originate from conditions of ambient stress which vary with epicentral region or magnitude.

scholarly journals Method to generate growth and degrowth models obtained from differential equations applied to agrarian sciences

2018 ◽  
Vol 39 (6) ◽  
pp. 2659 ◽  
Author(s):  
André Luiz Pinto dos Santos ◽  
Guilherme Rocha Moreira ◽  
Cicero Carlos Ramos de Brito ◽  
Frank Gomes-Silva ◽  
Maria Lindomárcia Leonardo da Costa ◽  
...  
Keyword(s):  
Differential Equations ◽  
Goodness Of Fit ◽  
Least Squares Method ◽  
Growth Curves ◽  
Information Criterion ◽  
Coefficient Of Determination ◽  
Absolute Deviation ◽  
Marquardt Algorithm ◽  
Maturation Rate ◽  
Biological Interpretation

This study aims to propose a method to generate growth and degrowth models using differential equations as well as to present a model based on the method proposed, compare it with the classic linear mathematical models Logistic, Von Bertalanffy, Brody, Gompertz, and Richards, and identify the one that best represents the mean growth curve. To that end, data on Undefined Breed (UB) goats and Santa Inês sheep from the works of Cavalcante et al. (2013) and Sarmento et al. (2006a), respectively, were used. Goodness-of-fit was measured using residual mean squares (RMS), Akaike information criterion (AIC), Bayesian information criterion (BIC), mean absolute deviation (MAD), and adjusted coefficient of determination . The models’ parameters (?, weight at adulthood; ?, an integration constant; ?, shape parameter with no biological interpretation; k, maturation rate; and m, inflection point) were estimated by the least squares method using Levenberg-Marquardt algorithm on the software IBM SPSS Statistics 1.0. It was observed that the proposed model was superior to the others to study the growth curves of goats and sheep according to the methodology and conditions under which the present study was carried out.

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