Measuring seismicity diversity and anomalies using point process models: case studies before and after the 2016 Kumamoto earthquakes in Kyushu, Japan

Kumazawa, Teruo; Ogata, Yosihiko; Tsuruoka, Hiroshi

doi:10.1186/s40623-017-0756-6

Cited by 12 publications

(7 citation statements)

References 41 publications

(40 reference statements)

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“…The standard stationary ETAS model can be temporally extended to the non-stationary ETAS model 22,[50][51][52] in the way that µ and K0 are assigned as a function of t. The function µ(t) and K0(t) are represented by a broken line connecting the respective sequences (ti, Data Fig. 2b,c), and a graph of timeseries of b-values again calculated by EMR, as shown in the top panel of Fig.…”

Section: Time-dependent µ and K0mentioning

confidence: 99%

Activated volcanism of Mount Fuji by the 2011 Japanese large earthquakes

Nanjo

Yukutake

Kumazawa

2022

Preprint

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The relation between earthquakes and volcanic eruptions, each of which is manifested by large-scale tectonic plate and mantle motions1, has been widely discussed2-7. Mount Fuji in Japan last erupted in 1707, paired with a magnitude (M)-9-class earthquake that took place 49 days prior8-10. Motivated by this pairing, previous studies examined the effect of both the 2011 M9 Tohoku megaquake and a triggered M6-class earthquake 4 days later at the foot of the volcano on Mount Fuji, although no volcanic eruption was reported11,12. More than 300 years already have passed since the last 1707 eruption, and although consequences to humans and society caused by the next eruption are already being considered, the implication for future volcanism remains uncertain. Here we show how volcanic low-frequency earthquakes (LFEs)14-18 in the deep part of the volcano revealed hitherto-unrecognized activation immediately after the foot earthquake. Our analyses19-27 showed that despite an increase in the rate of occurrence of LFEs, these did not return to pre-earthquake levels, indicating a change in the magma system. Our results demonstrate that the volcanism of Mount Fuji was reactivated by the foot earthquake, implying that this volcano is sufficiently sensitive to external events that are enough to trigger eruptions.

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Section: Time-dependent µ and K0mentioning

confidence: 99%

Activated volcanism of Mount Fuji by the 2011 Japanese large earthquakes

Nanjo

Yukutake

Kumazawa

2022

Preprint

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“…where the φ θ is the 2D B-spline function, and θ is the coefficient of function φ θ [35]. In this way, β is represented by a flexible function of location [34,35,[50][51][52]66].…”

Section: B Value Estimationmentioning

confidence: 99%

“…Ogata proposed the hierarchical space-time point-process models (HIST-PPM), cubic B-spline expansions and the Bayesian method for estimation and interpolation of b values in space [33][34][35][50][51][52][53]. As it does not require allocation of an earthquake sample, it may have advantages in computing spatial b values, particularly in highly fractured regions with complex fault systems, such as Yunnan Province, China.…”

Section: Introductionmentioning

confidence: 99%

Assessing Earthquake Forecast Performance Based on b Value in Yunnan Province, China

Wang

Chang

Miao

et al. 2021

Entropy

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Many studies have shown that b values tend to decrease prior to large earthquakes. To evaluate the forecast information in b value variations, we conduct a systematic assessment in Yunnan Province, China, where the seismicity is intense and moderate–large earthquakes occur frequently. The catalog in the past two decades is divided into four time periods (January 2000–December 2004, January 2005–December 2009, January 2010–December 2014, and January 2015–December 2019). The spatial b values are calculated for each 5-year span and then are used to forecast moderate-large earthquakes (M ≥ 5.0) in the subsequent period. As the fault systems in Yunnan Province are complex, to avoid possible biases in b value computation caused by different faulting regimes when using the grid search, the hierarchical space–time point-process models (HIST-PPM) proposed by Ogata are utilized to estimate spatial b values in this study. The forecast performance is tested by Molchan error diagram (MED) and the efficiency is quantified by probability gain (PG) and probability difference (PD). It is found that moderate–large earthquakes are more likely to occur in low b regions. The MED analysis shows that there is considerable precursory information in spatial b values and the forecast efficiency increases with magnitude in the Yunnan Province. These results suggest that the b value might be useful in middle- and long-term earthquake forecasts in the study area.

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“…Another way of extracting variations in the characteristics of seismic activity is to use a sophisticated model, such as the ETAS model (Ogata 1988). The use of such models requires assumptions about the spatiotemporal variations of model parameters to estimate which variations are most likely to explain the observed data (e.g., Ogata and Zhuang 2006;Kumazawa et al 2017). In the present study, however, we tried to make as few assumptions as possible and directly examine changes in the index values estimated from the observed data.…”

Section: Introductionmentioning

confidence: 99%

Statistical study on the regional characteristics of seismic activity in and around Japan: frequency-magnitude distribution and tidal correlation

Nagata¹,

Tamaribuchi²,

Hirose³

et al. 2022

Earth Planets Space

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We propose a statistical analysis method to identify common features of seismic activity that are indistinguishable from most other seismicity, and to find anomalous activity that differs from these common features. Using the hypocenter catalog of earthquakes which occurs in and around Japan during the past 20 years, we apply this method for the parameters of the frequency-magnitude distribution and a parameter that expresses the correlation of seismicity with tides as indices, with a focus on objectively understanding the regional characteristics of seismicity. As a result, we extracted a "typical" probability density distribution of each index value common to the most analysis regions and "anomalous" regions with index-value distributions that differ significantly from the typical distributions. In terms of the frequency-magnitude distribution, most estimated values of indices in the anomalous activity areas can be explained as variations corresponding to the effects of fluids, interplate coupling, and stress fields that control faulting styles that have been pointed out in previous studies. By extracting typical index values for the frequency-magnitude distribution, common features of the frequency-magnitude distribution that depend on the earthquake occurrence interval were identified. Although seismicity showed no clear correlation with tides, the index value for tidal correlation changes to reflect the proportion of earthquakes occurring in a series of periods shorter than the tidal period; it is therefore useful as an index to capture the characteristics of such earthquake occurrence intervals. We also show that the typical probability density distribution of these index values can be represented by existing models or their extensions. By using the proposed models as a reference, it is possible to quantify the degree of anomaly using the same concept as that of the method presented here; hence, such a method should be applicable to monitor seismic activity. Graphical Abstract

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Measuring seismicity diversity and anomalies using point process models: case studies before and after the 2016 Kumamoto earthquakes in Kyushu, Japan

Cited by 12 publications

References 41 publications

Activated volcanism of Mount Fuji by the 2011 Japanese large earthquakes

Activated volcanism of Mount Fuji by the 2011 Japanese large earthquakes

Assessing Earthquake Forecast Performance Based on b Value in Yunnan Province, China

Statistical study on the regional characteristics of seismic activity in and around Japan: frequency-magnitude distribution and tidal correlation

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