Controls on turbidite deposition offshore the Chilean convergent margin

在最近智利地震（Maule地区，2010年2月27日；M=8.8）破裂带的百年至千年时间尺度上，巨大俯冲带地震的复发率仍然高度不确定，但对地震危险性预测至关重要。浊积岩频率已被用来揭示沿地震危险大陆边缘的地震复发间隔，但这些结果仍然存在强烈的争议。只有了解浊积岩沉积的控制作用，才能成功地编制浊积岩古地震记录。为了确定反复发生的地震活动是浊流的触发因素，必须证明浊流在间隔广泛、孤立的沉积中心中的同步沉积。本研究的主要目的是评估智利边缘两个气气带全新世浊积沉积通量的相对贡献和控制历史。以陆地和海底组分及其相互作用为重点的深海沉积整体模型的发展将有助于评估编制浊积岩古地震记录的可行性。如果智利边缘被证明是一个合适的地方，那么将编制两个地震构造段的记录。提出的方法需要获得：(1)浊积层形成时间的可靠的地质年代学约束；(2)浊积层年龄和沉积速率与陆上和海上强迫记录的相关性；(3)在7个沉积中心测试同期浊积层沉积，以编制Maule（34º-38ºS）和邻近破裂带（30º-32ºS）的古地震记录。

Recurrence rates of giant subduction-zone earthquakes are still highly uncertain on centennial to millennial time scales along the rupture zone of the recent Chilean earthquake (Maule region, 2/27/2010; M=8.8), but are of utmost importance for seismic hazard prediction. Turbidite frequency has been used to reveal earthquake recurrence intervals along seismically hazardous continental margins but these results are still strongly debated. Only if the controls on turbidite deposition are well understood, the compilation of a turbidite paleoseismologic record can be successful. To establish recurring seismicity as a trigger for turbidity currents, synchronous deposition of turbidites in widely spaced, isolated depocenters has to be demonstrated. The main purpose of this study is to evaluate the relative contributions and history of controls on Holocene turbiditic sediment flux within two climatic zones along the Chilean margin. The development of a holistic model of deep-marine sedimentation focusing on terrestrial and submarine components and their interactions will allow to evaluate the feasibility of compiling a turbidite paleoseismologic record. If the Chilean margin proves to be a suitable place, such a record for two seismotectonic segments will be compiled. The proposed approach entails obtaining: (1) robust geochronologic constraints of the timing of turbidite layers, (2) correlation of turbidite ages and depositional rates to records of on- and offshore forcings, and (3) to test for coeval turbidite deposition in 7 depocenters to compile a paleoseismologic record for the Maule (34º-38ºS) and an adjacent rupture zone (30º-32ºS).