The b-value as an earthquake precursor

Smith, Warwick D.

doi:10.1038/289136a0

Cited by 261 publications

(125 citation statements)

References 11 publications

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“…It is known that aftershock activity becomes significantly quiescent preceding large aftershocks (Mtasu'ura 1986). However, any signatures ever proposed do not seem to be universal, since accelerating seismicity (e.g., Bowman et al 1998) and an increase in the b value (Smith 1981) were occasionally reported.…”

Section: Introductionmentioning

confidence: 98%

Anomalous decrease in relatively large shocks and increase in the p and b values preceding the April 16, 2016, M7.3 earthquake in Kumamoto, Japan

Nanjo

Yoshïda

2017

Earth Planets Space

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The 2016 Kumamoto earthquakes in Kyushu, Japan, started with a magnitude (M) 6.5 quake on April 14 on the Hinagu fault zone (FZ), followed by active seismicity including an M6.4 quake. Eventually, an M7.3 quake occurred on April 16 on the Futagawa FZ. We investigated if any sign indicative of the M7.3 quake could be found in the space-time changes in seismicity after the M6.5 quake. As a quality control, we determined in advance the threshold magnitude, above which all earthquakes are completely recorded. We then showed that the occurrence rate of relatively large (M ≥ 3) earthquakes significantly decreased 1 day before the M7.3 quake. Significance of this decrease was evaluated by one standard deviation of sampled changes in the rate of occurrence. We next confirmed that seismicity with M ≥ 3 was well modeled by the Omori-Utsu law with p ~ 1.5 ± 0.3, which indicates that the temporal decay of seismicity was significantly faster than a typical decay with p = 1. The larger p value was obtained when we used data of the longer time period in the analysis. This significance was confirmed by a bootstrapping approach. Our detailed analysis shows that the large p value was caused by the rapid decay of the seismicity in the northern area around the Futagawa FZ. Application of the slope (the b value) of the Gutenberg-Richter frequency-magnitude distribution to the spatiotemporal change in the seismicity revealed that the b value in the northern area increased significantly, the increase being Δb = 0.3-0.5. Significance was verified by a statistical test of Δb and a test using bootstrapping errors. Based on our findings, combined with the results obtained by a stress inversion analysis performed by the National Research Institute for Earth Science and Disaster Resilience, we suggested that stress near the Futagawa FZ had reduced just prior to the occurrence of the M7.3 quake. We proposed, with some other observations, that a reduction in stress might have been induced by growth of the slow slips on the Futagawa FZ.

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Section: Introductionmentioning

confidence: 98%

Anomalous decrease in relatively large shocks and increase in the p and b values preceding the April 16, 2016, M7.3 earthquake in Kumamoto, Japan

Nanjo

Yoshïda

2017

Earth Planets Space

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“…Wyss and Lee (1973) reported a decrease in the b-value before four out of five California earthquakes with magnitudes of 3.9 to 5.0. Smith (1981Smith ( , 1999 found that an increase in the bvalue was present for several years before the occurrence of large earthquakes and that the b-value decreased to normal in the short interval before the large event itself. Ogata and Katsura (1988) also found low b-values before large aftershocks.…”

Section: Introductionmentioning

confidence: 99%

Decreased b-value prior to the M 6.2 Northern Miyagi, Japan, earthquake of 26 July 2003

Tsukakoshi

Shimazaki

2008

Earth Planet Sp

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We developed a method to map and investigate temporal changes in the b-value using the signed Akaike information criterion (AIC) value and seismicity rate before the 2003 September 26-27 Northern Miyagi earthquake sequence. We studied the seismicity within a radius of 30 km around the epicenter of the largest shock, which was M 6.4, by three approaches: an analysis of all the events listed in the catalog; an analysis of only background events, but on data extracted by two different methods. We found that the change in the b-value of the clustered activities and background activities are different. The b-value of all events decreased from 1.2 to 0.7 and that of background event decreased even more. We empirically modeled the precursory temporal variation of the b-value and searched similar patterns among 971 areas chosen sequentially from inland Japan. The precursory pattern was both rare and significant; the AIC value was the second most significant factor among the more than 3000 tests conducted on 971 areas, each with four time windows. If the catalog was not declustered, the AIC of the precursory pattern became lower.

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“…Several precursor phenomena were observed and studied before strong earthquakes: the decrease in b-values (Suyehiro et al,1964;Smith, 1981), the appearance of zones of seismic quiescence, where the seismicity level was weaker than in the surrounding area (Wyss and Haberman, 1988;Wyss and Haberman, 1997), and the power-law increase in the cumulative energy of earthquakes (Bowman et al, 1998;Brehm and Braile, 1998;Jaume and Sykes, 1999;Main, 1999;Robinson, 2000). In addition, the seismicity clustering was observed before strong earthquakes (Zavialov and Nikitin, 1999;Giombattista and Tyupkin, 1999).…”

Section: Introductionmentioning

confidence: 99%

The pecularities of shear crack pre-rupture evolution and distribution of seismicity before strong earthquakes

Kiyashchenko

Troyan

2001

Nat. Hazards Earth Syst. Sci.

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Abstract. Several methods are presently suggested for investigating pre-earthquake evolution of the regions of high tectonic activity based on analysis of the seismicity spatial distribution. Some precursor signatures are detected before strong earthquakes: decrease in fractal dimension of the continuum of earthquake epicenters, cluster formation, concentration of seismic events near one of the nodal planes of the future earthquake, and others. In the present paper, it is shown that such peculiarities are typical of the evolution of the shear crack network under external stresses in elastic bodies with inhomogeneous distribution of strength. The results of computer modeling of crack network evolution are presented. It is shown that variations of the fractal dimension of the earthquake epicenters' continuum and other precursor signatures contain information about the evolution of the destruction process towards the main rupture.

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The b-value as an earthquake precursor

Cited by 261 publications

References 11 publications

Anomalous decrease in relatively large shocks and increase in the p and b values preceding the April 16, 2016, M7.3 earthquake in Kumamoto, Japan

Anomalous decrease in relatively large shocks and increase in the p and b values preceding the April 16, 2016, M7.3 earthquake in Kumamoto, Japan

Decreased b-value prior to the M 6.2 Northern Miyagi, Japan, earthquake of 26 July 2003

The pecularities of shear crack pre-rupture evolution and distribution of seismicity before strong earthquakes

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