地震寧靜及活化為重要的地震前兆活動，在過去的研究中時常被提出討論，但是大多屬於個案研究，因此始終缺乏一個系統性的方法應用於偵測這些地震前兆活動。新近發展出的PI (Pattern informatics)方法的計算不僅同時囊括了地震寧靜及地震活化，其直覺性的表示方法更是可協助指出地震異常發生之位置，唯獨其在計算方法受時間因素影響甚劇。因此我們將地震系統由自組織亞穩相變 (Self-organized spinodal, SOS) 所產生之行為引進到PI方法中, 利用地震的規模-頻率分布函數找出地震活化之時期，再以PI方法得到地震異常活動熱點圖 (PI map)。 將PI方法應用在集集及屏東地震兩個案例上，可以發現地震與板塊間的關聯性。集集地震的促發可能是如同薄皮理論所描述，因為與集集主震相關的地震大多來自於深度12公里內的地震；而屏東地震則是和深度在30公里至80公里間的地震較為相關，於是可推估屏東地震該是與板塊隱沒有所關聯。除此之外，藉由此兩案例的結果也可證實如活化等地震前兆會特別在中大型地震中突顯出來，並且這些中大型地震的規模會隨主震而有些微不同。 在研究地震異常活動熱點圖中，我們發現地震前兆活動在大震來臨前會向震央地區作遷移活動。我們利用震央與地震前兆活動點間的距離做近一步的研究，發現集集地震及屏東地震前，地震前兆活動點確實在時間上作對於震央的遷移運動。利用格點與地震前兆活動點間距離的關係曲線斜率，我們可以得到地震前兆活動於時間、空間上的遷移圖(Migration pattern)，我們發現在集集地震及屏東地震之例子中地震前兆活動都有向震央作遷移的行為，這種遷移行為可以裂縫結核(nucleation)作解釋。除此之外，從遷移圖在兩地震例子中的行為我們可以發現遷移行為的範圍及時間會隨地震大小而改變。根據此研究，我們不僅可以利用PI方法偵測地震前兆活動，更可利用延伸之方法了解地震活動行為，進而探討地震發生機制。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.
