1997 Fiscal Year Final Research Report Summary
Statistical Analyzes of Seismicity by Space-Time point process models
| Project/Area Number |
07680329
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Statistical science
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| Research Institution | The Institute of Statistical Mathematics |
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Principal Investigator |
OGATA Yoshihiko The Institute of Statistical Mathematics, Department of Statistical Methodology, Professor, 調査実験解析研究系, 教授 (70000213)
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| Co-Investigator(Kenkyū-buntansha) |
TANEMURA Masaharu The Institute of Statistical Mathematics, Department of Statistical Methodology,, 調査実験解析研究系, 教授 (80000214)
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| Project Period (FY) |
1995 – 1997
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| Keywords | Earthquake clusters / Probability forecast of events being foreshocks / Relative entropy / ETAS point-process model / Space-time point processes / Long-range dependence in time and space / Image visualization of space-time residuals / Modified Omori function of decaying aftershocks |
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| Research Abstract |
When a few earthquakes start to occur, it may be foreshock sequence to a larger earthquake, or it may be a swarm or simple mainshock-aftershock sequence. We have revealed some discriminating features of foreshocks relative to the other type of clusters, namely, the events' stronger proximity in time and space, and a tendency towards chronologically increasing magnitudes, in addition to the first event's geographic location. These features have led us to construct models which forecast the probability of the earthquakes being foreshocks. The validation of the forecast has been demonstrated.
The correlation between characteristic parameters of statistical models, such as the b-value of the Gutenberg-Richter relation, the p-value of the modified Omori formula, the p- and alpha-value of the ETAS point process model, and the fractal dimension D of the hypocenter distribution, is analyzed for 34 aftershock sequences in Japan from 1971 to 1995. The contrasting correlation patters are revealed between the parameters for the intraplate and interplate earthquakes except the two pairs (b, D) and (alpha, p) where the similar correlation patterns are found.
Several space-time statistical models are constructed based on both classical empirical studies of clustering and some more speculative hypothese. We also made further practical extensions of the model to sitations where the background seismicity is spatially non-homogeneous, and the clusters are non-isotropic. The goodness-of-fit of the models is compared for two high quality data sets, in different tectonic regions. AIC allows the details of the clustering structure in space to be clarified. The simulated data sets show the similar spatial distributions to the real ones, but differ from them in some features of space-time clustering which may provide useful indicators of directions for further study.
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