Changes in Seismicity Pattern Due to the 2016 Kumamoto Earthquakes Identify a Highly Stressed Area on the Hinagu Fault Zone

Nanjo, Kazuyoshi; Izutsu, Jun; Orihara, Yoshiaki; Kamogawa, Masashi; Nagao, Toshiyasu

doi:10.1029/2019gl083463

Cited by 26 publications

(33 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…b-value estimation. Spatial temporal changes in b are known to reflect a state of stress in the Earth's crust 13,15,42 and to be influenced by asperities and frictional properties 24,43 and by an interface locking along subduction zones 26,44,45 . The results of laboratory experiments indicate a systematic decrease in the b-value approaching the time of the entire fracture 11,12,14 .…”

Section: Methodsmentioning

confidence: 99%

Were changes in stress state responsible for the 2019 Ridgecrest, California, earthquakes?

Nanjo

2020

Nat Commun

Self Cite

View full text Add to dashboard Cite

Monitoring the Earth's stress state plays a role in our understanding of an earthquake's mechanism and in the distribution of hazards. Crustal deformation due to the July 2019 earthquake sequence in Ridgecrest (California) that culminated in a preceding quake of magnitude (M) 6.4 and a subsequent M7.1 quake caused stress perturbation in a nearby region, but implications of future seismicity are still uncertain. Here, the occurrence of small earthquakes is compared to larger ones, using b-values, showing that the rupture initiation from an area of low b-values, indicative of high stress, was common to both M6.4 and M7.1 quakes. The post-M7.1-quake sequence reveals that another low-b-value zone, which avoided its ruptured area, fell into an area near the Garlock fault that hosted past large earthquakes. If this area were more stressed, there would be a high-likelihood of further activation of seismicity that might influence the Garlock fault.

show abstract

Section: Methodsmentioning

confidence: 99%

Were changes in stress state responsible for the 2019 Ridgecrest, California, earthquakes?

Nanjo

2020

Nat Commun

Self Cite

View full text Add to dashboard Cite

show abstract

“…The mainshock magnitudes were also similar (M7.1 vs. M7.3) and had the strike‐slip mechanisms. It is difficult to pin point the common stress conditions and state of faults that lead to the occurrence of both sequences but some clues may be inferred from the seismicity patterns that preceded and followed both events and can be related to the changes in the stress field (Nanjo, 2020; Nanjo et al., 2019).…”

Section: Discussionmentioning

confidence: 99%

Statistics and Forecasting of Aftershocks During the 2019 Ridgecrest, California, Earthquake Sequence

Shcherbakov

2021

JGR Solid Earth

View full text Add to dashboard Cite

The 2019 Ridgecrest, California, earthquake sequence represents a complex pattern of seismicity that is characterized by the occurrence of a well‐defined foreshock sequence followed by a mainshock and subsequent aftershocks. In this study, a detailed statistical analysis of the sequence is performed. Particularly, the parametric modeling of the frequency‐magnitude statistics and the earthquake occurrence rate is carried out. It is shown that the clustering of earthquakes plays an important role during the evolution of this sequence. In addition, the problem of constraining the magnitude of the largest expected aftershocks to occur during the evolution of the sequence is addressed. In order to do this, two approaches are considered. The first one is based on the extreme value theory, whereas the second one uses the Bayesian predictive framework. The latter approach has allowed to incorporate the complex earthquake clustering through the Epidemic Type Aftershock Sequence (ETAS) process and the uncertainties associated with the model parameters into the computation of the corresponding probabilities. The results indicate that the inclusion of the foreshock sequence into the analysis produces higher probabilities for the occurrence of the largest expected aftershocks after the M7.1 mainshock compared to the approach based on the extreme value distribution combined with the Omori‐Utsu formula for the earthquake rate. Several statistical tests are applied to verify the forecast.

show abstract

“…These findings suggest that more accumulated stress was released at shallower depths. an afterslip-dominated region and viscoelastic deformation-dominated region (Nanjo et al 2019). They suggested that there was a local increase in the stresses at the boundary between regimes dominated by different postseismic deformation processes based on the aftershock decay law of Utsu (1961) and a seismicity rate model inferred from the stressing history (Dieterich 1994).…”

Section: Discussionmentioning

confidence: 99%

“…The 6 differential stress generally increases as the b-value decreases, and vice versa. Many studies have examined the stress states in various tectonic settings using spatiotemporal b-value distributions (e.g., Chiba 2019Chiba , 2020Ghosh et al 2008;Nanjo and Yoshida 2018;Nanjo et al 2016Nanjo et al , 2019Schorlemmer et al 2004;Schorlemmer and Wiemer 2005;Tormann et al 2015). The highly stressed areas in any tectonic setting, such as regions with a large coseismic slip and large slip deficit rate, are usually characterized by low b-values.…”

Section: B-valuesmentioning

confidence: 99%

Stress State Inferred from b Value and Focal Mechanism Distributions in the Aftershock Area of the 2005 West Off Fukuoka Prefecture Earthquake

Chiba

2021

Pure Appl. Geophys.

View full text Add to dashboard Cite

The spatiotemporal stress states in the aftershock region of the 2005 west off Fukuoka prefecture earthquake are examined via an analysis of the b-values and focal mechanism solutions. The aftershocks are aligned roughly NW-SE, with the southeastern part of the aftershock region believed to correspond to Kego Fault, which extends beneath the Fukuoka metropolitan area. This study reveals depth-dependent b-values in the focal region, where the b-values (b = 0.7-1.4) are generally higher above the mainshock depth (9.5 km) and lower (b = 0.5-1.0) at greater depths. The shallower region possesses a significant temporal increase in b-values, whereas a lateral b-value heterogeneity is observed in the deeper region. The b-values (b ~ 1.0) near the mainshock are relatively high, whereas the northwestern and southeastern edges of the deep region have lower b-values (b = 0.5-0.7). On the other hand, many of the focal mechanisms for the ≥ 3.5 events are located in the low b-value area of the deep region. The stress-tensor inversion results reveal a change in stress state from strike-slip to strike-slip/normal faulting.These findings imply that the stress state remains high and/or slightly decreased in the northwestern and southeastern parts of the deep region. These results and the findings of previous research on this earthquake sequence suggest that the likelihood of future large earthquakes along the southeastern part of the aftershock region should be considered relatively high.

show abstract

Changes in Seismicity Pattern Due to the 2016 Kumamoto Earthquakes Identify a Highly Stressed Area on the Hinagu Fault Zone

Cited by 26 publications

References 33 publications

Were changes in stress state responsible for the 2019 Ridgecrest, California, earthquakes?

Were changes in stress state responsible for the 2019 Ridgecrest, California, earthquakes?

Statistics and Forecasting of Aftershocks During the 2019 Ridgecrest, California, Earthquake Sequence

Stress State Inferred from b Value and Focal Mechanism Distributions in the Aftershock Area of the 2005 West Off Fukuoka Prefecture Earthquake

Contact Info

Product

Resources

About