Global survey of aftershock area expansion patterns

Tajima, Fumiko; Kanamori, Hiroo

doi:10.1016/0031-9201(85)90066-4

Cited by 155 publications

(99 citation statements)

References 52 publications

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“…Less than 20 events are used for each case study. While the case for the diffusion of aftershocks is relatively strong [Kagan andKnopoff, 1976, 1978;von Seggern et al, 1981;Tajima and Kanamori, 1985] but still controversial, the migration of foreshocks towards the mainshock area, suggested using a stacking method [e.g., Kagan andKnopoff, 1976, 1978;von Seggern et al, 1981;Reasenberg, 1985] is even less clearly observed.…”

Section: Migration Of Foreshocksmentioning

confidence: 99%

Mainshocks are aftershocks of conditional foreshocks: How do foreshock statistical properties emerge from aftershock laws

2003

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The inverse Omori law for foreshocks discovered in the 1970s states that the rate of earthquakes prior to a mainshock increases on average as a power law ∝ 1/(t c − t) p ′ of the time to the mainshock occurring at t c . Here, we show that this law results from the direct Omori law for aftershocks describing the power law decay ∼ 1/(t − t c ) p of seismicity after an earthquake, provided that any earthquake can trigger its suit of aftershocks. In this picture, the seismic activity at any time is the sum of the spontaneous tectonic loading and of the activity triggered by all preceding events weighted by their corresponding Omori law. The inverse Omori law then emerges as the expected (in a statistical sense) trajectory of seismicity, conditioned on the fact that it leads to the burst of seismic activity accompanying the mainshock. In particular, we predict and verify by numerical simulations on the Epidemic-Type-Aftershock Sequence (ETAS) model that p ′ is always smaller than or equal to p and a function of p, of the b-value of the Gutenberg-Richter law (GR) and of a parameter quantifying the number of direct aftershocks as a function of the magnitude of the mainshock. The often documented apparent decrease of the b-value of the GR law at the approach to the main shock results straightforwardly from the conditioning of the path of seismic activity culminating at the mainshock. However, we predict that the GR law is not modified simply by a change of b-value but that a more accurate statement is that the GR law gets an additive (or deviatoric) power law contribution with exponent smaller than b and with an amplitude growing as a power law of the time to the mainshock. In the space domain, we predict that the phenomenon of aftershock diffusion must have its mirror process reflected into an inward migration of foreshocks towards the mainshock. In this model, foreshock sequences are special aftershock sequences which are modified by the condition to end up in a burst of seismicity associated with the mainshock. Foreshocks are not 2 just statistical creatures, they are genuine forerunners of large shocks as shown by the large prediction gains obtained using several of their qualifiers.

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Section: Migration Of Foreshocksmentioning

confidence: 99%

Mainshocks are aftershocks of conditional foreshocks: How do foreshock statistical properties emerge from aftershock laws

2003

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“…For example, the 1-year aftershock area of the 1971 earthquakes in source 17 covered the adjacent source 16, while the 1-day aftershock area was confined in the source 17 (Tajima and Kanamori, 1985). On the other hand, the earthquake catalogue used concerns present century data only.…”

Section: Discussionmentioning

confidence: 99%

“…McCann et al (1979) and Nishenko and McCann (1981) developed a set of three major temporal categories to reflect their assessment of the relative seismic potential, the completeness of the seismic history and the understanding of the tectonic regime for major plate boundaries in and around the margins of the Pacific Ocean and the the maximum magnitude of the earthquake, on the seismicity level, on the type of faulting and on geomorphological criteria. The dimensions of aftershock zones and source areas of recent events (Tajima and Kanamori, 1985) and the divisions of McCann et al (1979), Nishenko and McCann (1981) and Nishenko (1991) were also used Black circles show epicenters of main shocks while open circles show epicenters of foreshocks and aftershocks. The terms foreshock and aftershock are meant in their broad sense, since a model is sought that can predict the main shocks in each seismogenic source, i.e., the strong earthquakes which occur at the beginning and the end of each seismic cycle and not smaller earthquakes that occur during the preseismic and postseismic activations.…”

Section: Introductionmentioning

confidence: 99%

Long Term Earthquake Prediction in the New Guinea-Bismarck Sea Region Based on the Time and Magnitude Predictable Model.

Karakaisis

1993

J,Phys,Earth

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The New Guinea-Bismarck Sea region has been divided into 17 seismogenic sources on the basis of certain seismological and geomorphological criteria. In each of these sources the interevent times between successive main shocks with magnitudes equal to or larger than certain cut-off magnitudes were considered. These interevent times as well as the magnitudes of the main shocks have been used to determine the following relations: log Tt = 0.36Mmin + 0.28Mp -0.49 logMo + 9.58, ME = 0 .74Mmin-0.31Mp+ 0.49logMo-8.53, where Tt is the calculated interevent time measured in years, Mmin is the magnitude of the smallest main shock considered, Mp and ME are the magnitudes of the preceding and the expected main shocks and Mo is the yearly released seismic moment in each source. On the basis of these relations and considering the date and the magnitude of the last main shock, conditional probabilities for the next 10 years (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002) and the magnitude of the expected main shock in each source were determined.

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“…The aftershock distribution for the 17:47 20 September 1999 M w 7.45 Chi-Chi earthquake Taiwan is shown in Fig. 1 (Tajima and Kanamori 1985). In order to understand the spatial variations in b values, we divide the aftershock zone (Fig.…”

Section: Data Collection and Analysismentioning

confidence: 99%

Aftershock Hazard Magnitude, Time, and Location Probability Forecasting

Chen¹,

Tsai²,

Chang³

et al. 2014

Terr. Atmos. Ocean. Sci.

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This study combines branching aftershock sequence (BASS) and modified Omori's law to develop a predictive model for forecasting the magnitude, time, and location of aftershocks of magnitude M w ≥ 5.00 in large earthquakes. The developed model is presented and applied to the 17:47 20 September 1999 M w 7.45 Chi-Chi earthquake Taiwan, 09:32 5 November 2009 (UTC) Nantou M w 6.19, 00:18 4 March 2010 (UTC) Jiashian M w 6.49 earthquake sequences, Taiwan, and 05:46 11 March 2011 (UTC) Tohoku M w 9.00 earthquake, Japan. The estimated peak ground acceleration (PGA) results are remarkably similar to calculations from the recorded magnitudes in both trend and level. This study proposes an empirical equation to improve the aftershock occurrence forecast time. The forecast time results were greatly improved. The magnitude of aftershocks generally decreases with time. It was found that the aftershock forecast probability of M w ≥ 5.00 is high in the first six days after the main shock. The results will be of interest to seismic mitigation specialists.Spatial and temporal seismicity parameters to the aftershock sequence investigation into the 17:47 20 September 1999 (UTC) M w 7.45 Chi-Chi earthquake, Taiwan found that immediately after the earthquake the area closest to the epicenter had a lower b value. This pattern suggests that at the time of the Chi-Chi earthquake, the area closest to the epicenter remained prone to large magnitude aftershocks and strong shaking. With time, however, the b value increased, indicating a reduced likelihood for large magnitude aftershocks.

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Global survey of aftershock area expansion patterns

Cited by 155 publications

References 52 publications

Mainshocks are aftershocks of conditional foreshocks: How do foreshock statistical properties emerge from aftershock laws

Mainshocks are aftershocks of conditional foreshocks: How do foreshock statistical properties emerge from aftershock laws

Long Term Earthquake Prediction in the New Guinea-Bismarck Sea Region Based on the Time and Magnitude Predictable Model.

Aftershock Hazard Magnitude, Time, and Location Probability Forecasting

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