The seismic cycle in subduction zones: quantification of deformation rates and strain partitioning in the 1960 Chile earthquake segment

俯冲带产生了地球上最大的地震；在那里，人们认为距离上一次地震发生的时间越长，下一次地震S滑动的幅度就越大，因此震级也会随之增加。然而，历史和古地震数据显示了不同的大俯冲地震的复发时间和震级，这并不一定遵循这个逻辑预测。了解这个知之甚少的问题是至关重要的。所有超过力矩震级(MW)9级的历史事件都发生在板块斜向会聚的俯冲带。然而，地震和大地测量数据表明，同震滑动发生在与S走向几乎垂直的位置，这意味着斜向会聚在边缘存在某种分割。应变分配在地震旋回中的作用，以及应变分配程度的瞬时变化如何调节大俯冲地震的复发时间和震级的机制，尚未得到充分的探索。智利中南部的瓦尔迪亚地震段是研究地震旋回和应变分配过程的合适试验场，它在1960年产生了仪器记录的最大地震，震级为9.5兆瓦。该项目试图通过确定：(1)瓦尔迪亚地段南段地震周期的形变率；(2)破译大俯冲地震的重复间隔；(3)描述地震周期内的应变分配预算，从而深入了解这一问题。通过综合绘制地貌和构造图、对弧前和弧内地区变形的第四纪地貌进行同位素测年、使用连续的和动态的全球定位系统测量现代形变率以及通过综合构造模拟，可以最好地实现这些目标。

Subduction zones have generated the largest earthquakes on Earth; there, it has been thought that the longer the time since the last earthquake, the larger the next earthquake s slip, and consequently magnitude will be. However, historical and paleoseismic data has shown variable recurrence times and magnitude of large subduction earthquakes, which not necessarily follow this logical predictor. Gaining insight into this poorly understood problem is of utmost importance. All historical events that exceeded moment magnitude (Mw) 9 occurred in subduction zones where plate convergence is oblique. However, seismic and geodetic data show that coseismic slip occurred nearly normal to the megathrust s strike, implying that oblique convergence is somehow partitioned across the margin. The role of strain partitioning in the seismic cycle and the mechanism as to how transient variations in the degree of partitioning could modulate recurrence times and magnitudes of great subduction earthquakes, has not been fully explored. The Valdivia earthquake segment in south-central Chile, which in 1960 generated the largest, instrumentally recorded earthquake with Mw 9.5, is a suitable testing ground to study the seismic cycle and strain partitioning processes. This project attempts gaining insight into this problematic by determining: (1) deformation rates over the seismic cycle in the southern sector of the Valdivia segment; (2) deciphering the recurrence interval of large subduction earthquakes; and (3) characterizing the strainpartitioning budget over the seismic cycle. These objectives are best achieved through combined geomorphic and structural mapping, isotopic dating of deformed Quaternary landforms in the foreand intra-arc regions, measuring present-day deformation rates using continuous and campaign GPS, and by integrative tectonic modeling.