Collaborative Research: Tracing the Geomorphic Signature of Strike-Slip Faulting in Marlborough Hill Country, South Island, New Zealand

当走滑断层活动时，它是地球上最危险的地质特征之一。目前，详细描述它们的滑移率、地震危险性和在一系列时间尺度上的演化向地球科学界提出了挑战。在描述走滑断层方面，一个未被充分利用的工具是定量分析地貌对断层横向运动的响应，以便直接从地貌中提取构造信息。目前，这种性质的研究通常只关注山脉系统中的垂直运动。这项研究将开发一个新的框架，将地貌分析应用于走滑断层系统，这样做将推动科学界对地貌对地壳横向运动的响应有更全面和更定量的了解，而这是我们目前缺乏的。新西兰南岛有一套平行的右旋走滑断层，称为马尔伯勒断层系统(MFS)，为解决这一问题提供了一个极好的天然实验室。从北到南，断层起始年龄和累积断层位移被认为是减小的，而滑动速率增加了4倍以上，提供了断层演化不同阶段的快照。利用MFS作为自然实验，该项目将测试地表过程和地貌可以在多大程度上用作侧向断层活动的量化指标。地貌学、热年代学和数值模拟将被用来记录区域侵蚀历史，识别不同滑移率、断层年龄和垂直运动程度的地区在景观形态上的差异(或相似之处)，并利用景观演化模型对不同走滑断层情景的地表响应进行定量预测。这项工作的主要目标是检验景观响应在多大程度上可以作为走滑断层活动的指示。研究马尔伯勒断裂系统内走滑断裂的地貌响应，有可能提高我们对水平断裂带活动和地貌对断层运动的响应的理解，在这个位置和一般情况下，最终减轻与生活在走滑断裂及其周围相关的危险。地震活动经常发生在大马尔伯勒地区，包括沿以前未知的断层(例如2010年破坏性的达菲尔德7.1级地震和2011年克赖斯特彻奇6.3级地震)。这项工作的结果将有助于在这个地点以及世界上许多其他对活动走滑断层知之甚少的地点进行地震危险性评估。对MFS内主要断裂带以及次级收缩构造中垂直运动的时间和幅度的详细研究也将为新西兰造山带的构造演化提供新的制约因素，并促进美国和新西兰地质学家之间已经很强的国际合作。

When active, strike-slip faults are among the most dangerous geologic features on Earth. At present, characterizing in detail their slip rates, seismic hazard, and evolution over a range of timescales challenges the earth science community. An under-exploited tool in strike-slip fault characterization is quantitative analysis of the geomorphic response to lateral fault motion to extract tectonic information directly from the landscape. At present, studies of this nature typically focus solely on vertical motion in mountain systems. This research will develop a new framework for applying geomorphic analysis to strike-slip fault systems and in doing so, will move the scientific community toward a more comprehensive and quantitative understanding of the geomorphic response to lateral crustal motion, which we currently lack. A suite of parallel right-lateral strike-slip faults known as the Marlborough Fault System (MFS), South Island, New Zealand offers an excellent natural laboratory for this problem. From north to south, fault initiation ages as well as cumulative fault displacement are thought to decrease whereas slip rates increase over four fold, providing snapshots of different stages of fault evolution. Using the MFS as a natural experiment, this project will test the degree to which surface processes and landforms can be used as a quantitative indicator of lateral fault activity. Geomorphology, thermochronology, and numerical modeling will be applied to document regional erosion history, identify differences (or similarities) in landscape morphology between regions of variable slip rate, fault age, and degree of vertical motion, and make quantitative predictions about the surficial response to different strike-slip fault scenarios using landscape evolution models.The primary goal of this work is to test the degree to which landscape response can be used as an indicator of strike-slip fault activity. Studying the landscape response to strike-slip faulting within the Marlborough Fault System has the potential to improve our understanding of horizontal fault zone activity and the geomorphic response to fault motion, at this location and in general; ultimately mitigating the hazards associated with living in and around strike-slip faults. Seismic activity occurs frequently within the greater Marlborough region, including along faults that were previously unknown (as in the case of the destructive Darfield 2010 magnitude 7.1 and Christchurch 2011 magnitude 6.3 earthquakes). Results from this work will benefit seismic hazard assessment at this location, as well as at many other locations around the world where far less is known about active strike-slip faulting. Detailed study of the timing and magnitude of vertical motion along the primary fault strands as well as along the secondary contractional structures within the MFS will also provide new constraints on the tectonic evolution of the New Zealand orogen and foster already strong international collaboration between U.S. and New Zealand geologists.