過去十年之間台灣本島內發生了多次災害性的地震，除了人們所熟知的集集地震之外，尚有：1993年的大埔地震、1994年的南澳地震、1998年的瑞里地震，以及1999年的嘉義地震。雖然這些地震造成民眾財產甚至生命上的損失，但由於在台灣許多地震儀器的記錄之下，提供了地震以及相關的研究充足的資料。本研究便根據過去十年間，數個較大地震之餘震分佈，探討該地區構造地質的性質。
在從事觀測地震研究時，地震定位之精確性總是影響所得結果的優劣，地震定位的精確性是由數個因素所控制：測站的分佈、所得的波相、到時讀取的精確性以及對於地殼構造的了解。一般的地震定位誤差常介於數公里至數十公里之間，由於過大的誤差會導致不良的結果，因此本研究利用「雙差分地震定位演算法」( Double Difference Earthquake Location Algorithm, Waldhauser, F., Ellsworth, W. L., 2000 ) 進行地震重新定位，比較發現，在重新定位後有明顯改善資料品質的情形，對該地區構造及形貌的判讀也更加精確及容易。最後得到以下結果：
在重新定位各大地震餘震的結果，所得到的結果大部分都相當的良好（除了集集地震因為其餘震分佈過於分散，且大部分都位處在速度構造複雜、測站稀少的中央山脈地區，其餘的餘震在重新定位後誤差皆在500公尺以內），因此對於本研究之判斷地下構造有相當大的助益。最後得出：大埔地震為破裂於東北-西南走向、向西傾斜之斷層面，根據附近的地質構造推論，大埔地震應為存在於地下之盲斷層所造成；南澳地震為破裂於東-西走向、幾乎垂直於地表之斷層面，根據附近的地質構造推論，南澳地震應為鹿皮溪斷層所造成；瑞里地震為破裂於東北-西南走向、向東傾斜之斷層面 ，根據附近的地質構造推論，瑞里地震應為大尖山或觸口斷層所造成；嘉義地震為破裂於南-北走向、向西傾斜之斷層面，根據附近的地質構造推論，嘉義地震應為位於盲斷層之地震。

The distribution of aftershocks often indicates the geological structure in that area and implies the type of fault rupture. Except of 1999 Chi-chi earthquake, most of earthquake in Taiwan did not cause surface rupture. It yields the ambiguous on determination of rupture plane and its associated active fault. More accurate relocation of aftershocks might be able to help us on identification of its rupture plane and understanding its corresponding geological structure.
In this paper, we reexam the aftershocks of several large earthquakes in the past ten years e.g. 1993 Da-Pu, 1994 Nan-Ao, 1998 Ruey-Li, 1999 Chi-Chi and 1999 Chia-I earthquakes. Using CWBSN data, we apply the “Double Difference Earthquake Location Algorithm” ( Waldhauser, F., Ellsworth, W. L., 2000 ) to relocate aftershocks and to understand their association with geological structure. Because of the concept of multiplet (a group of earthquake which are close to each other), so the algorithm can filter the error from the ray path and improve the data quality.

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