Segmentation of the 2010 Maule Chile earthquake rupture from a joint analysis of uplifted marine terraces and seismic-cycle deformation patterns
Segmentation of the 2010 Maule Chile earthquake rupture from a joint analysis of uplifted marine terraces and seismic-cycle deformation patterns
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DOI：
10.1016/j.quascirev.2015.01.005
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发表时间：
2015-04
影响因子：
4
通讯作者：
J. Jara‐Muñoz;D. Melnick;D. Brill;M. Strecker
中科院分区：
文献类型：
--
作者：
J. Jara‐Muñoz;D. Melnick;D. Brill;M. Strecker
俯冲带中主要断裂系统的分段控制着地震的震级和位置，但分段边界的存在原因以及长期形变与地震破裂程度之间的关系却知之甚少。我们比较了2010年莫勒地震(M8.8级)破裂带上的永久性变形模式和地震周期变形模式，这场地震破裂了智利俯冲边缘500公里的区域。利用LiDAR地形学分析了MIS5海相阶地的形态，并通过12个发光年龄、地层学和地貌对比，建立了它们的年代学和同时代成因，获得了整个断裂带几乎连续的隆升速率分布。这些阶地的平均抬升速率为0.5米/卡。这一数值在经历了高达1.6米/卡的快速浮现的三个地区超过；它们分别位于断裂带的北段、中段和南段，分别称为Topocalma、Carranza和Arauco。这三个地段与1730年以来的八次大地震的边界相关。位于2010年断裂边界的Topocalma和Arauco扇区由宽阔的地壳翘曲带组成，波长分别为60和90千米。这两个区域与整个安第斯边缘的造山斜弯曲轴线重合，并与板块界面曲率的变化相关。反过来，Carranza的快速隆起波长较短，与三条地壳规模的正断层的下盘挠曲有关。Carranza的抬升速率与板块耦合以及同震滑动呈负相关，表明永久形变可能在地震间积累。我们认为，Arauco和Topocalma的隆起带反映了巨型逆冲摩擦性质的变化，从而阻碍了大地震的传播。1960年(M9.5级)和2010年事件期间的滑动与阿劳科∼90公里长的快速隆起区重叠；同样，2010年和1906年的滑动延伸到托波卡尔马巨型逆冲的∼60公里长的部分，但这一地区完全被1730年(M∼9)事件打破，该事件向南传播，直到卡兰萨。Arauco和Topocalma都显示出至少自中更新世以来持续快速抬升的证据。因此，这两个区段可能构成了离散的地震构造边界，对大地震破裂的限制最大，但不是全部。根据我们的观察，这种障碍可能会在多段超周期事件中被突破。
The segmentation of major fault systems in subduction zones controls earthquake magnitude and location, but the causes for the existence of segment boundaries and the relationships between long-term deformation and the extent of earthquake rupture, are poorly understood. We compare permanent and seismic-cycle deformation patterns along the rupture zone of the 2010 Maule earthquake (M8.8), which ruptured 500 km of the Chile subduction margin. We analyzed the morphology of MIS-5 marine terraces using LiDAR topography and established their chronology and coeval origin with twelve luminescence ages, stratigraphy and geomorphic correlation, obtaining a virtually continuous distribution of uplift rates along the entire rupture zone. The mean uplift rate for these terraces is 0.5 m/ka. This value is exceeded in three areas, which have experienced rapid emergence of up to 1.6 m/ka; they are located at the northern, central, and southern sectors of the rupture zone, referred to as Topocalma, Carranza and Arauco, respectively. The three sectors correlate with boundaries of eight great earthquakes dating back to 1730. The Topocalma and Arauco sectors, located at the boundaries of the 2010 rupture, consist of broad zones of crustal warping with wavelengths of 60 and 90 km, respectively. These two regions coincide with the axes of oroclinal bending of the entire Andean margin and correlate with changes in curvature of the plate interface. Rapid uplift at Carranza, in turn, is of shorter wavelength and associated with footwall flexure of three crustal-scale normal faults. The uplift rate at Carranza is inversely correlated with plate coupling as well as with coseismic slip, suggesting permanent deformation may accumulate interseismically. We propose that the zones of upwarping at Arauco and Topocalma reflect changes in frictional properties of the megathrust resulting in barriers to the propagation of great earthquakes. Slip during the 1960 (M9.5) and 2010 events overlapped with the ∼90-km-long zone of rapid uplift at Arauco; similarly, slip in 2010 and 1906 extended across the ∼60-km-long section of the megathrust at Topocalma, but this area was completely breached by the 1730 (M∼9) event, which propagated southward until Carranza. Both Arauco and Topocalma show evidence of sustained rapid uplift since at least the middle Pleistocene. These two sectors might thus constitute discrete seismotectonic boundaries restraining most, but not all great earthquake ruptures. Based on our observations, such barriers might be breached during multi-segment super-cycle events.