強烈的地震對於人類生命財產安全均有很大的危害，而台灣地區因位處板塊邊界，板塊運動導致地震活動相當頻繁，所以研究其發震的構造便顯得重要。探就地震的發生因為地下岩層中累積的應力能量釋放，某個區域能夠容納應力能量的多寡取決於岩層本身的性質、所處溫度及壓力。由於岩石越接近熔點越具有可塑性而可累積來釋放之應力能量會變小許多，進而讓地震次數與釋放能量也減少。故到了某一深度後，岩石會產生脆-塑性轉變(Brittle-ductile transition)，同時地震也減少，所以這個轉變帶也決定是否有地震的轉變帶(Seismic-aseismic transition)。本研究利用台灣地區1991年1月至2008年10月的地震資料，希望勾勒出台灣地區的發震深度，來預測台灣各斷層區域所能夠產生的最大地震規模。本研究計算D95作為各區域的發震深度值，D95為該區域所有地震資料依照發震深度大小排列後，其上方95%地震資料和下方5%地震資料的分隔深度。我們發現在台灣各地震分區中所能發生最大地震規模之值最大的在外海之琉球海溝系統，最大可能產生地震規模8.0的強震，而最小值則是新竹地區的6.9。其他重要之斷層如車籠埔斷層(Mw7.8)、彰化斷層(Mw7.8)、屯子腳斷層(Mw6.5)、梅山斷層(Mw6.4)、新化斷層(Mw6.2)、潮州斷層(Mw7.3)等。

Strong earthquakes have severe influences on human’s life, property, and safety. Taiwan is located in the plate boundary, the plate movement lead to frequent intense earthquake activities, such that the seismogenic structure of Taiwan becomes important. Where the earthquake occurred is related to the energy release of the underground rocks. The energy for an area can accommodate depends on the rock formation, temperature condition, and pressure. When the temperature of the rock closer to its melting point, it will become more plastic and the ability to accumulate and release the strain energy becomes smaller, which let the earthquake numbers diminish. So after it comes to some depth, the rock will become more ductile, and the earthquake number will also diminish, such a transition is called brittle-ductile transition and the depth is called the seismogenic thickness. So the brittle-ductile transition also called the seismic-aseismic transition. Our research used Taiwan earthquake data from January 1991 to October 2008. We determined the seismogenic thickness of Taiwan area, and to predict the maximum capable earthquake magnitude for each major fault zones of Taiwan. Our research used the so called D95. According to the focal depths of the earthquakes, the separation of the top 95% earthquake data and the 5% bottom earthquake data is defined as the seismogenic thickness. We calculated D95 for different area to estimate the value of seismogenic thickness. We found that the biggest capable earthquake size in the Taiwan area is in offshore eastern Taiwan and the earthquake magnitude is Mw8.0, and the smallest value is the Mw6.9 of Hsin-Chu area. Other important faults such as Chelungpu fault (Mw7.8), Changhua fault (Mw7.8), Tuntzuchiao fault (Mw6.5), Meishan fault (Mw6.4), Hsinhua (Mw6.2), Chaochow fault (Mw7.3) and so on.

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