震後應力改變誘發斷層破裂之評估

The Assessment of Triggering Fault Rupture by Postseismic Stress Change

本研究對三種基本型態（正、逆與走－滑）斷層的地震，以理論的方式計算庫倫應力的改變（△CFS），這改變的庫倫應力對鄰近斷層的影響，與斷層本身的幾何型態有關，因此，要得到確切庫倫應力的影響，就必須將應力做座標轉換至有效斷層面上來討論。本研究以固定的區域範圍，計算可以誘發破裂的區域，做為斷層誘發破裂的機率，來評估斷層誘發的可能性，結果發現當破裂的斷層為走－滑斷層時，其鄰近被誘發破裂的機率以走－滑與正斷層較大，逆斷層機率較小；當破裂的斷層為逆斷層時，其鄰近被誘發機率山大至小依次為走－滑斷層、逆斷層、正斷層系統；當破裂的斷層為正斷層時，其鄰近被誘發機率山大至小則為正斷層、走－滑斷層、逆斷層系統。另一方面，對於空間中不同型態的斷層系統，它們被誘發破裂的機率則為：對走－滑斷層系統，被誘發的機率，以走－滑斷層與逆斷層破裂時機率較大，正斷層破裂時機率較小；對逆斷層系統，被誘發的機率，以逆斷層與走－滑斷層破裂時機率較大，正斷層破裂時機率較小；對正斷層系統，被誘發的機率由大至小則為走－滑斷層、正斷層、逆斷層破裂。因此，經過這些討論可以瞭解各類斷層誘發破裂的趨勢，對於餘震誘發研究以及震後危險區域的評估可提供一些重要的依據。

In this study, the 3 fundamental types （normal, thrust and strike-slip） of fault's earthquakes by theoretical method to calculate the static Coulomb failure stress changes, △CFS. The change of stress affect around of the fault system is related with its geometry. Therefore, In order to obtain the influence of exact Coulomb stress, the coordinate of stress must be transform to the effective fault plane for discussing. In this study, we fixed the area around the rupture fault and calculating the region which can be triggered. The triggered region is induced breakdown, as the probability of fault rupture induced to assess the possibility of fault-induced. The results are when the rupture fault is the strike-slip type, the triggering possibility of fault system is the strike-slip is approximately equal the normal and higher than the thrust. When the rupture fault is the thrust type, the triggering possibility of fault system is that the strike-slip is higher than the thrust and the thrust is higher than the normal. When the rupture fault is the normal type, the triggering possibility of fault systems is that the normal is higher than the strike-slip and the strike-slip is higher than the thrust.On the other hand, for the difference types of fault systems in space, their triggered rupture possibility are, for the strike-slip fault system, the triggered rupture possibility is that the strike-slip is approximately equal the thrust and higher than the normal. For the thrust fault system, the triggered rupture possibility is that the strike-slip is approximately equal the thrust and higher than the normal. For the normal fault system, the triggered rupture possibility is that the strike-slip is approximately equal the normal and higher than the thrust. So, after these discussions, we can understand the triggered rupture trend of the different types of faults. For the researches of aftershock triggered and the assessment of postseismic dangerous area, this study can provide the important basis.