| Summary: | 博士 === 國立中央大學 === 地球物理研究所 === 98 === Since earthquake system is a complex system with unobservable dynamics, the pattern informatics (PI) method applying the concept of pattern dynamics may help us detect systematic fluctuations from observed seismicity. To make the PI method more efficient, the analysis of frequency-magnitude distributions (FMD) based on the self-organized spinodal (SOS) behavior was introduced in the PI method. The signatures of anomalous activity associated with the precursory seismic activation before the Chi-Chi and Pingtung earthquakes were revealed in this retrospective study. In addition, the PI maps show that the Chi-Chi and Pingtung earthquakes are mainly associated with the earthquakes in the depth range 0–12 km and 30—80 km, respectively. The PI maps also suggest that the occurrence of precursory phenomena such as activation is mainly in moderate earthquakes.
The PI migration before the Chi-Chi and the Pingtung earthquakes can be identified from the PI maps. A migration pattern can be made by calculating the distances between hotspots and sites. The migration of the PI hotspots implies a preparation process before large earthquakes. The duration of this preparation process can persist for several years, and it increases with the size of impending event. But, migration is active mainly in stage 2 of SOS behavior and stops after stage 3. This migration process might be associated with the nucleation of earthquakes and the increase of the number of moderate events in stage 3 might reflect the accelerating behavior of seismicity. Not only the time period but also the range of the migration varies with the size of the forthcoming mainshock. To construct the relation between the two parameters and the size of an earthquake would be helpful for forecasting the magnitude of a future event.
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