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

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.

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 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

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.

Short-term retrospective forecasting of earthquakes based on temporal variations of the b-value of the magnitude-frequency distribution

2020 ◽  
Author(s):  
Paolo Gasperini ◽  
Emanuele Biondini ◽  
Antonio Petruccelli ◽  
Barbara Lolli ◽  
Gianfranco Vannucci
Keyword(s):  
Frequency Distribution ◽  
High Probability ◽  
High Stress ◽  
B Value ◽  
Temporal Variations ◽  
Short Term ◽  
Differential Stress ◽  
B Values ◽  
Probability Of Occurrence ◽  
Seismic Catalog

<p>In some recent works it has been hypothesized that the slope (b-value) of the magnitude-frequency distribution of earthquakes may be related to the differential stress inside the crust.  In particular, it has been observed that low b-values are associated with high stress values and therefore with high probability of occurrence of strong seismic shocks. In this paper we formulate a predictive hypothesis based on temporal variations of the b-value. We tested and optimized such hypothesis retrospectively based on the homogenized Italian instrumental seismic catalog (HORUS) from 1995 to 2018. A comparison is also made with a similar predictive hypothesis based on the occurrence of strong foreshocks.</p><p> </p>

scholarly journals Fractal Characterization of Earthquake occurrences in Nigeria

2019 ◽  
Vol 1 ◽  
pp. 281-287
Author(s):  
N N Abdulsalam ◽  
O Ologe
Keyword(s):  
Fractal Dimension ◽  
Active Zone ◽  
Hazard Analysis ◽  
B Value ◽  
Google Earth ◽  
Counting Method ◽  
Microsoft Word ◽  
Box Counting ◽  
Box Counting Method

Fractal characterization of Earthquake occurrences in Nigeria was carried out in order to know the b-value of tremor occurrences in the country. This will help in hazard analysis and research in the geological and geophysical structures of Nigeria. The method used in determining the b-value is the box counting method, but for simplicity, we used circle. The areas that are tremor prone were posted on a digitized Nigeria map using Google earth and Surfer 7.0 software. The computation with the box counting method was performed with picked radius of the circle from 50km - 350km and the average number of points that falls within each circle were recorded. The graph of log r (the logarithms of radius of circle or scale) against log <N> (logarithms of average number of points) was plotted using grapher and excels Microsoft word and the slope of the graph was determined. The determined slope gave the fractal dimension and the b-value was thus calculated. In this work, a b-value of 0.6 was obtained indicating that Nigeria falls within seismically less active zone.

scholarly journals Spatial Variations in Seismicity Characteristics in and Around the Source Region of the 2019 Yamagata-Oki Earthquake, Japan

2020 ◽  
Author(s):  
Taku Ueda ◽  
Aitaro Kato ◽  
Yoshihiko Ogata ◽  
Lina Yamaya
Keyword(s):  
Source Region ◽  
B Value ◽  
Spatial Variations ◽  
Japan Meteorological Agency ◽  
Earthquake Catalog ◽  
Shear Strain Rate ◽  
Study Region ◽  
Etas Model ◽  
Seismicity Rate ◽  
Background Seismicity

Abstract The 2019 {\text{M}}_{\text{j}} 6.7 Yamagata-Oki Earthquake occurred adjacent to the northeastern edge of the source region of the 1964 {\text{M}}_{\text{j}} 7.5 Niigata Earthquake, offshore of Yamagata Prefecture, Japan. Few aftershocks occurred in the source region of the Yamagata-Oki earthquake immediately following the Niigata earthquake, and the recent seismicity rate in this region is extremely low compared with that of the surrounding region. This spatial variation in seismicity may allow us to elucidate plausible physical processes that shape the spatiotemporal evolution of these shallow-crustal environments. Here, we investigate the spatial variations in seismicity characteristics by applying the HIerarchical Space–Time Epidemic Type Aftershock Sequence (HIST-ETAS) model to an earthquake catalog compiled by the Japan Meteorological Agency for events in and around the Yamagata-Oki earthquake rupture region. We compare spatial variations in the background seismicity rate and aftershock productivity estimated from the HIST-ETAS model with the geophysical features in the study region. The background seismicity rate is high along the eastern margin of the Sea of Japan and correlates well with a previously identified zone that possesses a high geodetic shear strain rate. The two major earthquakes occurred in and around an active shear zone, suggesting that the background seismicity rate may serve as a key parameter for evaluating seismic hazard across the Japanese Archipelago. Furthermore, the source region of the Yamagata-Oki earthquake has a higher aftershock productivity, lower b-value, and lower seismic-wave velocity than that of the Niigata earthquake. We interpret this low-velocity zone to be a well-developed damaged rock that resulted in both a reduction in the b-value and an increase in aftershock productivity based on previous laboratory experiments and numerical results; this damage makes the rock more ductile at the macroscopic scale. The higher ductility in the source region of the Yamagata-Oki earthquake may have worked as a soft barrier against the propagation of dynamic rupture that occurred during the Niigata earthquake.

scholarly journals Homogenized earthquake catalog and b-value mapping for Ethiopia and its adjoining regions

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Geremew Lamessa ◽  
Tilahun Mammo ◽  
Tarun K.Raghuvanshi
Keyword(s):  
Red Sea ◽  
B Value ◽  
Moment Magnitude ◽  
Ethiopian Rift ◽  
Rift System ◽  
Earthquake Catalog ◽  
Gulf Of Aden ◽  
East African Rift System ◽  
Main Ethiopian Rift ◽  
B Values

AbstractThe Ethiopian rift which is part of East African Rift system passes through the middle of the country making it one of the most seismically active regions in the world. Thus, significant and damaging earthquakes have been reported and recorded in the past in this region. A homogeneous earthquake catalog is of basic importance for studying the earthquake occurrence pattern in space and time and for many engineering applications including assessment of seismic hazard, estimation of peak ground accelerations and determination of long-term seismic strain rates.The first earthquake catalogue for Ethiopia was prepared by Pierre Gouin and later, different authors attempted to compile a catalogue using different time period intervals and different earthquake magnitude scales. The b-value mapping and its implication never done for Ethiopia and its environs. The main purpose of the study is therefore first compile and homogenize earthquake catalog of Ethiopia including Read Sea and Gulf of Aden regions into Moment magnitude Mw scale through completeness analysis in time and magnitudes. Secondly, mapping b-values for different Seismgenic regions and understand its implications for magma induced Seismicity in the regions.During the present study, a new homogenized earthquake catalog in moment magnitude scale (Mw), covering about 3814 events is prepared for Ethiopia including Red sea and Gulf of Aden regions. The present study area is bounded within Latitude (40N − 200)N and Longitude (340N − 480)N E and have a magnitude range of Mw (3.0–7.1) with a total coverage period of 56 years (1960 to 2016). The catalog has been analyzed for magnitude completeness (Mc) using Gutenberg’s Frequency Magnitude Distribution law and it is found to be complete respectively for Mc ≥ 4.6 ± 0.03, Mc ≥ 4.6 ± 0.03, Mc ≥ 3.2, Mc ≥ 3.1 and Mc ≥ 5.1 for Afar including red sea and Gulf of Aden, Afar rift and Dabbahu Volcano, Northern, Central, and Southern Main Ethiopian Rifts. Further, the corresponding average b-value of the regions Afar including Red Sea and Gulf of Aden, Afar and Dabbahu Volcano separately, Northern Main Ethiopian Rift, Central Main Ethiopian Rift and Southern Main Ethiopian Rift respectively are estimated to be 1.17 ± 0.05, 1.15 ± 0.05, 0.843, 0.826 and 1.03 with respective period of completeness from 2003 to 2014, 2005 to 2014, 2001 to 2003, 2001 to 2003 and 1960 to 2016 for the regions. Later, mapping of the b-values in the Gutenberg-Richter relation from the newly developed catalog was performed by binning the regions into minimum of 0.050x0.050 for Afar and Dabbahu region, 0.10x0.10 for Main Ethiopian rifts and 0.20x0.20 for the other regions. Thus, the b-value characteristics of various seismogenic zones within the area have been discussed. Hence, in this study, we clearly observed that magma chamber movement including mapping of volcanic centers and magmatic segments are mapped using b-values.

Correlation between earthquake b value and VP/VS ratio in Japan

2021 ◽  
Author(s):  
Pei-Ying Wu ◽  
Sean Kuanhsiang Chen ◽  
Yih-Min Wu
Keyword(s):  
Pore Pressure ◽  
Earth Science ◽  
B Value ◽  
The Other ◽  
Japan Meteorological Agency ◽  
Likelihood Method ◽  
Earthquake Catalog ◽  
Injection Wells ◽  
B Values ◽  
Value Determination

&lt;p&gt;Earthquake b value is primarily controlled by differential stress in the crust. Pore pressure has also been reported influencing b value locally. In nature, the influence can only be observed in the subsurface crust by injection wells. It remains unclear whether the influence of pore pressure on b value can be observed in the scale of the entire crust. To this end, we assume that pore pressure increases proportionally with V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S&lt;/sub&gt; ratio, which is derived from seismic tomography studies, to examine correlation between V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S&lt;/sub&gt; ratio and b value. We investigated this correlation in Japan because it is one of the most earthquake-prone countries with dense seismic networks and high-quality earthquake catalogs. We used an earthquake catalog from the Japan Meteorological Agency from 1998 to 2011 Feb to calculate the b values in the inland region of Japan above the 30 km depth. The selected period is based on a stable completeness of magnitude (M&lt;sub&gt;c&lt;/sub&gt;) since 1998 and the strong clustering effects by the both 2011 Tohoku and 2016 Kumamoto earthquakes. We then calculated M&lt;sub&gt;c&lt;/sub&gt; and b value by maximum curvature method and maximum likelihood method, respectively, in the grids of 0.1 &amp;#160;0.1 &amp;#160;10 km with a radius of 30 km from the center of the grids. The b value determination requires the number of earthquakes with magnitudes greater than the M&lt;sub&gt;c &lt;/sub&gt;over 150 within the radius. For the V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S&lt;/sub&gt; ratios, we used the latest data derived from the National Research Institute for Earth Science and Disaster Resilience, Japan, to resample them to the same grids as b values. We simply resampled the V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S&lt;/sub&gt; ratios by either averaging them into the grids of b values, or weighting them through a triangular function to the grids center of b values in depths. We analyzed b value as a function of V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S&lt;/sub&gt; ratio and binned the b values within every 0.01 V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S&lt;/sub&gt; interval to calculate the means and medians for liner regressions. Our preliminarily results show that there is little correlation between entire b values and V&lt;sub&gt;P&lt;/sub&gt;/V&lt;sub&gt;S &lt;/sub&gt;ratios among different depth ranges (0-10 km, 10-20 km, 20-30 km). We observed a linear negative relation in the binned data at the 10-20 km depth, however, this relation is not likely observed in the other depths. It may imply that the influence of pore pressure on b value could vary with depths. We&amp;#8217;ll calculate the b values using entire magnitude range method and compare the results to the other localized geophysical observations.&lt;/p&gt;

scholarly journals Spatial Variation of b-Values and Their Relationship with the Fault Blocks in the Western Part of the Tibetan Plateau and Its Surrounding Areas

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 1016
Author(s):  
Hamid Hussain ◽  
Zhang Shuangxi ◽  
Muhammad Usman ◽  
Muhammad Abid
Keyword(s):  
Tibetan Plateau ◽  
B Value ◽  
Strike Slip ◽  
The Tibetan Plateau ◽  
Gorkha Earthquake ◽  
Study Region ◽  
B Values ◽  
Fractured Medium ◽  
Surrounding Areas ◽  
Near Future

The Tibetan Plateau is considered to be one of the best natural laboratories for seismological research. This study sought to determine the spatial variations of b-values in the western part of the Tibetan Plateau, along with its surrounding areas, and the relation with the region’s fault blocks. The study region lies within 27–36.5° N, 78–89° E, and its fracture structure consists of strike-slip faults, as well as normal and thrust faults. A catalog record from 2009–2019 provided 4431 well-centered earthquakes that varied in magnitude from 0.1 to 8.2 M. The record was obtained from China’s seismological network, which is capable of recording low magnitudes to analyze b-values in the study area. The key findings of this study are as follows: (1) the range of earthquake depth in the region was 0–256 km, with the depth histogram showing a high frequency occurrence of shallow earthquakes in the area; (2) a time histogram showed that the major earthquakes occurred between 2014–2015, including the notable 2015 Gorkha earthquake (M = 8.2); (3) the b-value computed in the study area was 0.5 to 1.6, but in most of the study area, the b-value ranged from 0.6 to 0.9, which was a low to intermediate value, due to the presence of strike-slip faults in the central part of the study area and underthrusting in the region (south of the study area); and (4) a high b-value was found in the northwestern and eastern regions of the area, which proved that the area is prone to small earthquakes in the near future. The study also showed that the central and southern areas of the study region had low to intermediate b-values, meaning that it is prone to destructive and massive earthquakes with high magnitudes, such as the Gorkha earthquake (southern part of the study area). Low b-values revealed the degree of variation in rock properties, including large stress and strain, a fractured medium, a high deformation rate, and large faults. Small b-values were observed when the stress level was high in the investigated region, which might be used to predict a massive high-magnitude earthquake in the near future.

scholarly journals Evaluation of global seismicity along Northern and Southern hemispheres

2020 ◽  
Author(s):  
Olaide Sakiru Hammed ◽  
Theophilus Aanuoluwa Adagunodo ◽  
Musa Oluwafemi Awoyemi ◽  
Joel Olayide Amosun ◽  
Tokunbo Sanmi Fagbemigun ◽  
...  
Keyword(s):  
Focal Depth ◽  
B Value ◽  
Tectonic Stress ◽  
Study Region ◽  
Earthquake Parameters ◽  
B Values ◽  
Earthquake Energy ◽  
Global Seismicity ◽  
Northern And Southern Hemispheres ◽  
Earthquake Data

Abstract. An earthquake has been identified as one of the major natural disasters that cause loss of lives and property. To mitigate this disaster, knowledge of global seismicity is essential. This research is aimed at evaluating the Gutenberg Richter b-value parameter and focal depth distribution of earthquake parameters to identify the prominent earthquake-prone zones in the Northern and Southern hemispheres. The study area covers 20° to the Northern and Southern hemispheres, with the equator in the middle. The data were obtained from the earthquake catalogue of the Advanced National Seismic System (ANSS) hosted by the Northern California Earthquake Data Centre USA from 1963–2018. Fifty-four-year earthquake data of M ≥ 6.0 were processed and analyzed using Gutenberg-Richter (GR). The b-value parameters obtained from the GR model were plotted against the hemispheres using bar chart graphs to determine the tectonic stress level of the study region. The earthquake energy released was evaluated along the Northern and Southern hemispheres for a proper understanding of seismic events in the study region. It was observed that the rate of earthquake occurrence at the Southern hemisphere is higher than the Northern hemisphere. The b-values obtained in all the zones vary from 0.82–1.16. At the same time, the maximum earthquake energy of 4.6 × 1025 J was estimated. Low b-values indicate high tectonic stress within the plates. The large tectonic stress accumulation around the equator suggests that unstable lithospheres characterize this zone.

Temporal b-value variation before and after ML ≥ 6.0 Taiwan earthquakes from 2012 to 2019

2021 ◽  
Author(s):  
Po-Yuan Chen ◽  
Sean Kuanhsiang Chen ◽  
Yih-Min Wu
Keyword(s):  
Physical Process ◽  
Large Earthquake ◽  
B Value ◽  
Likelihood Method ◽  
Earthquake Catalog ◽  
B Values ◽  
Stress Changes ◽  
Before And After ◽  
Window Approach ◽  
Central Weather Bureau

&lt;p&gt;Recent studies show that earthquake b values gradually decrease before large earthquakes at the epicenters and then immediately increase after the earthquakes. Temporal b-value variations may result from crustal stress changes associated with a large earthquake. However, the physical process is rarely observed and remains unclear. Taiwan island is a young orogeny leading to frequent earthquakes with magnitudes greater than M&lt;sub&gt;L&lt;/sub&gt; 6.0, which provides an excellent laboratory to examine the physical process. We calculated b-value variation before and after M&lt;sub&gt;L&lt;/sub&gt; &amp;#8805; 6.0 Taiwan earthquakes at the epicenters from 2012 to 2019. The time period is based on an enhancement of earthquake detection capability from the Central Weather Bureau Seismic Network in Taiwan, which allows the magnitude of completeness (M&lt;sub&gt;c&lt;/sub&gt;) down to 1.5 in the inland region. We used a relocated earthquake catalog to precisely estimate b value and M&lt;sub&gt;c &lt;/sub&gt;by the maximum likelihood method and maximum curvature method, respectively. We designed three steps in our research. First, we calculated the b value and M&lt;sub&gt;c&lt;/sub&gt; at the epicenters of the M&lt;sub&gt;L&lt;/sub&gt; &amp;#8805; 6.0 earthquakes in overall 8 years to know the background seismic activity. Based on this, second, we calculated b values and M&lt;sub&gt;c&lt;/sub&gt; per half year to test the sensitivity between the radius from epicenters (r) and the number of earthquakes with magnitudes greater than M&lt;sub&gt;c&lt;/sub&gt;&amp;#160;(n). Finally, we will apply moving window approach with specific criteria to continuously calculate temporal b-value variations. Our results showed that spatial b values in Taiwan in overall 8 years have an average of 1.0. The b values are systematically lower in the epicenters of M&lt;sub&gt;L&lt;/sub&gt; &amp;#8805; 6.0 earthquakes from 2012 to 2019. We have determined suitable r and n values for each earthquake at the epicenters and some epicenters share similar r and n values. We preliminarily observed temporal b-value decreases before the 2018 M&lt;sub&gt;w&lt;/sub&gt; 6.4 Hualien earthquake. Considering temporal b-value variation by moving windows, we aim to realize whether temporal b-value variation by a large earthquake can be frequently observed in Taiwan.&lt;/p&gt;

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