EAPSI: Quantifying Tectonic Controls on Changing Segmentation of Oceanic Transform Faults

大洋转换断层（TF）是构造板块的边界，它是适应构造板块沿沿着洋中脊（MORs）运动的基础。虽然传统上被定义为单个边界偏移莫尔的两个段，但是TF可以分裂成几个故障链，并且随后重新统一为单个迹线。分段TF的形成可能是由于整个TF的伸展构造运动。相反，分段TF的统一可能与挤压构造运动有关，然而，这种演变的过程知之甚少。海底的结构特征，如断裂带（FZs），断层和岩石圈变形产生的地形，记录了板块运动的构造响应，倾斜于原来的TF。 在与海洋地质学、挠曲和构造学专家、忠南国立大学的Seung-Sep Kim博士的合作下，PI将量化太平洋中部先前分割的Clarion FZ的统一过程。TF的分割和统一可以随着时间的推移改变板块边界的位置。本研究的主要目的有三：1）利用主持研究员Kim博士提供的克拉里昂FZ地区最近获得的高分辨率测深资料，识别变形的类型和分布; 2）利用二维数值模型分析分段FZ的挠曲演化; 3）我们将通过比较模型预测的重力异常（FZ弯曲演化的代理）与船上测量，评估克拉里昂FZ的构造条件。为了量化压缩对TF统一的假设影响，我们的模型将比较压缩应变的各种速率和幅度，FZ的年龄偏移，以及变换内扩展段的数量，年龄和几何形状与预测的弯曲剖面。 最后，利用这些结果，我们计划开发预测的比例律，构造压缩的位置和时间的TF unified.This根据东亚和太平洋夏季研究所计划奖励支持由美国研究生的夏季研究，是由美国国家科学基金会和韩国国家研究基金会共同资助。

Oceanic transform faults (TFs) are tectonic plate boundaries that are fundamental to accommodating tectonic plate motions along mid-ocean ridges (MORs). Although classically defined as a single boundary offsetting two segments of a MOR, TFs can split into several fault strands and subsequently re-unify to a single trace. Formation of segmented TFs is likely due to extensional tectonic motions across the TF. Conversely, unification of segmented TFs may be associated with compressional tectonic motions, however, the processes governing this evolution are poorly known. Structural features on the ocean floor, such as fracture zones (FZs), faults, and topography produced by lithospheric deformation, record tectonic responses to plate motions oblique to the original TF. In collaboration with Dr. Seung-Sep Kim of Chungnam National University, an expert in marine geology, flexure, and tectonics, the PI will quantify the processes that govern unification of the previously segmented Clarion FZ in the central Pacific Ocean. Segmentation and unification of TFs can alter the location of plate boundaries over time. Quantifying segmentation processes will enhance our understanding of evolving plate boundaries as well as their magmatic and seismic expressions.The research has 3 primary goals: 1) Using recently acquired high-resolution bathymetry over the Clarion FZ provided by the host researcher, Dr. Kim, we will identify styles and distributions of deformation; 2) We will analyze flexural evolution of a segmented FZ using 2D numerical models; 3) We will assess the tectonic conditions of the Clarion FZ through time by comparing model-predicted gravity anomalies (a proxy for flexural evolution of a FZ) to shipboard measurements. To quantify the hypothesized effect of compression on TF unification, our models will compare various rates and magnitudes of compressional strain, age offsets across the FZ, as well as the number, age, and geometry of intra-transform spreading segments to predicted flexural profiles. Finally, using these results we plan to develop predictive scaling laws that relate tectonic compression to the location and timing of TF unification.This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the National Research Foundation of Korea.