Basically, due to the storage of strain energy for many years, the locking segment of the fault is more dangerous than the creeping segment that continuously releases energy. Creeping fault is characterized by slow and nearly continuous slip and generally do not produce large earthquakes. However, a Mw 6.5 earthquake event occurred on 6 July 2017 and ruptured the creeping segment of Philippine fault on the Leyte Island near the Tongonan geothermal field, which is a crucial topic to characterize the along-strike and down-dip spatial distribution of seismic and aseismic creeping segments and patches. 基本上,由於應變能的儲存多年,故障的鎖定段比不斷釋放能量的爬行段更危險。蠕動斷層的特點是緩慢且幾乎連續的滑動,通常不會產生大地震。然而,2017年7月6日發生了Mw 6.5級地震事件,導致通戈南地熱田附近萊特島菲律賓斷層的爬升段破裂,這是表徵地震和地震爬升段和斑塊的沿走向和下傾空間分佈的關鍵課題。
In this study, the Leyte segment of the Philippine fault provides a good opportunity 在本研究中,菲律賓斷層的萊特島段提供了一個很好的機會
to study creeping behavior and fault characteristics from creeping to locked segment. It also allows us to understand the mechanisms of this strike-slip fault and assess the seismic hazard. The understanding of fault behavior is limited due to the scarcity of seismic and geodetic stations on the Leyte Island. We used the Persistent Scatterers Interferometry Synthetic Aperture Radar (PS-InSAR) technique with ALOS PALSAR data to obtain the LOS (Line of Sight) velocity field across the Leyte segment in this study. In order to understand the relationship between the creep phenomenon and the interseismic slip rate on the fault plane, we have established a simple elastic model to invert the interseismic slip rate on the fault plane from the PS-InSAR data. 研究從爬行到鎖定段的蠕動行為和斷層特徵。它還使我們能夠瞭解這種走滑斷層的機制並評估地震危險。由於萊特島上地震站和大地測量站的稀缺性,對斷層行為的理解是有限的。在本研究中,我們使用持續散射體干涉合成孔徑雷達 (PS-InSAR) 技術和 ALOS PALSAR 數據來獲得整個萊特島段的 LOS(視線)速度場。為了理解蠕變現象與斷面地震間滑移率之間的關係,我們建立了一個簡單的彈性模型,根據 PS-InSAR 數據反演了斷面上的地震間滑移率。
Chapter 2. Active Deformation in Leyte Segment of the Philippine fault 第 2 章.菲律賓斷層萊特島段的主動變形
2.1 Tectonic Setting and Geological Background 2.1 構造環境和地質背景
The Philippine archipelago are an orogenic belt that is created by the subduction and collision of oceanic and continental plate (Karig, 1983) and it is bounded by two trench systems that subduct in opposite directions (Fitch, 1972). The east-dipping Manila Trench forms parts of its western boundary and together with the Negros-Sulu-Cotabato Trench, absorbs the convergence along the western side (Fig. 2.1). The west-dipping Philippine Trench and the Luzon Trough forms its eastern boundary and absorbs the convergence along the eastern side. 菲律賓群島是由海洋板塊和大陸板塊的俯衝和碰撞形成的造山帶(Karig, 1983),它以兩個向相反方向俯衝的海溝系統為界(Fitch, 1972)。東傾的馬尼拉海溝構成了其西部邊界的一部分,並與內格羅斯-蘇祿-哥打巴托海溝一起吸收了沿西側的匯合(圖 2.1)。西傾的菲律賓海溝和呂宋海槽形成其東部邊界,並吸收了東側的匯合。
The Philippine Fault transects the Philippine archipelago and is a 1,200km1,200 \mathrm{~km} long sinistral strike-slip fault that results from the partitioning of the oblique convergence between the Philippine Sea Plate and Eurasia Plate (Aurelio, 2000). Fitch (1972) proposed a model of oblique convergence between two lithospheric plates. The component of convergence parallel to the plate boundary generates a major strike-slip fault system behind the subduction zone. This appears to be the case in tectonics of Philippine archipelago. Figure 2.2 demonstrates the shear partitioning model of Fitch’s 1972 hypothesis. Due to the convergence between the Sunda Plate and the Philippine Sea plate, a series of island arc volcanoes are produced in the Philippine archipelago. 菲律賓斷層橫切菲律賓群島,是菲律賓 1,200km1,200 \mathrm{~km} 海板塊和歐亞板塊之間斜交會合分裂的長正弦走滑斷層(Aurelio,2000 年)。Fitch (1972) 提出了兩個岩石圈板塊之間斜向會聚的模型。平行於板塊邊界的收斂分量在俯衝帶後面產生了一個主要的走滑斷層系統。菲律賓群島的構造似乎就是這種情況。圖 2.2 演示了 Fitch 1972 年假設的剪切分區模型。由於巽他板塊和菲律賓海板塊的交匯,菲律賓群島產生了一系列島弧火山。
Figure 2.1 The tectonic setting of Philippines. White line with triangles shows the trench system nearby Philippine. White line represents the trace of Philippine fault. Big white vector shows the convergent rate of the Philippine Sea Plate and Eurasian Plate. 圖 2.1 菲律賓的構造環境。帶三角形的白線表示菲律賓附近的海溝系統。白線表示菲律賓斷層的痕跡。白色大向量顯示了菲律賓海板塊和歐亞板塊的收斂速率。