Collaborative Research: Seismic characterization of microearthquakes and crustal velocity structure around the Whataroa fault zone drilling site, Alpine Fault, New Zealand

合作研究：新西兰高山断层瓦塔罗阿断层带钻探现场周围微地震和地壳速度结构的地震特征

• 批准号: 1114147
• 负责人: Steven Roecker
• 金额: $ 23.78万
• 依托单位: Rensselaer Polytechnic Institute
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2017-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1114147&HistoricalAwards=false
• 关键词: Collaborative; Research; Seismic; characterization; microearthquakes

The mechanical behavior of large faults is controlled by thermal, chemical, and hydraulic factors,as well as each fault's intrinsic structure and the ambient stresses. Understanding what conditionsprevail within the interiors of active faults is crucial for elucidating the mechanisms governinglong-term fault evolution and, in particular, the earthquake rupture process. This project involvesa detailed study of microearthquakes and crustal structure within and surrounding the AlpineFault, South Island, New Zealand, around the Whataroa fault zone drilling site. It will be carriedout close collaboration with a team of New Zealand scientists. The key scientific issues to beaddressed by this research project include: (1) determining the geometry of the AF to mid-crustaldepths and the depth to the base of the seismogenic zone, (2) determining focal mechanisms andestimating principal stress orientations, (3) seismic imaging of crustal structure using multiplemethods, and (4) searching for possible nonvolcanic tremor (NVT). Our project is designed totest a number of hypotheses, including: (1) that the complexity of the surface fault trace does notreflect the fault trace at depth, rather the partitioning seen at the surface merges into a throughgoingfault with oblique slip in the upper crust; (2) that the depth to the base of the seismogeniczone is elevated to 15 km, or perhaps shallower, on the AF beneath the Whataroa area; (3) thatthe AF dip remains close to 50° to the base of the seismogenic zone; (4) that principal stressorientations do not vary with distance from the AF; (5) that the relatively low velocity zoneimaged at large scale through much of the crust along the SIGHT transects is actually a narrowerzone closer to the AF, similar to the resistivity model; (6) that NVT is not present beneath theAF.The goal of this project is to examine the structure and microearthquake characteristics of amajor active continental fault, the Alpine Fault, South Island, New Zealand. The Alpine Fault islate in its earthquake cycle and is the focus of a long-term, multidisciplinary scientificinvestigation. In this project, we will carry out seismic field work and subsequent analyses ofmicroearthquakes associated with the Alpine Fault. The research will be conducted inconjunction with an ambitious fault zone drilling project focused on the mechanical properties ofthe Alpine Fault and the adjacent crust. Their work will help (1) define the geometry of the faultat depth, (2) determine the depth range of seismic activity (the "seismogenic zone"), (3) establisha three-dimensional structural context for interpreting borehole observations and core, and (4)potentially help to define rupture zones of shallow earthquakes as future drilling targets.

大断层的机械行为由热，化学和氢气因子以及每个断层的内在结构和环境应力控制。了解主动断层内部盛行的哪些条件对于阐明统治期断层演化的机制，尤其是地震破裂过程至关重要。该项目参与了Whataroa断层区钻探地点周围的Alpinefault，新西兰South Island，South Island and Alpinefault内外的微夸克和地壳结构的详细研究。它将与新西兰科学家团队进行密切合作。该研究项目要划分的关键科学问题包括：（1）确定AF到中部末期的几何形状以及对地震生成区域基础的深度，（2）确定焦点机制，并估算原理压力取向，（（3）使用多重构造和（4）搜索（4）搜索（4）搜索的colustal colustal结构。我们的项目被设计为许多假设，包括：（1）表面故障迹线的复杂性确实在深度处得到了故障迹线，而是在表面上看到的分区，将其分配到上沿着上皮中的斜滑; （2）在Whataroa区域下方的AF上，地震基因基因的深度升高到15公里，或者可能较浅； （3）AF浸入接近地震区的底部50°； （4）主应力不会随距AF的距离而变化； （5）相对低速度通过沿视线样带的大部分地壳大规模区分区域图像实际上是一个狭窄的区域，与AF相似，类似于耐药模型； （6）NVT不存在于theaf下。该项目的目的是检查Amajor主动连续断层的结构和微观特征，新西兰南岛的高山断层。高山断层在其地震周期中存在，并且是长期多学科科学审查的重点。在这个项目中，我们将进行地震现场工作，并随后对与高山断层相关的微电视进行分析。这项研究将与雄心勃勃的断层区钻井项目进行不合格，该项目的重点是高山断层和相邻地壳的机械性能。他们的工作将有助于（1）定义断层深度的几何形状，（2）确定地震活性的深度范围（“地震生成区”），（3）建立了三维结构背景，用于解释井眼观测和核心，以及（4）潜在地将未来钻探目标的破裂的重裂动量定义为钻探目标。