Collaborative Research: Unlocking the secrets of slow slip by drilling at the northern Hikurangi subduction margin, New Zealand: CORK observatory development and installation

合作研究：通过在新西兰 Hikurangi 俯冲边缘北部钻探解开慢滑移的秘密：CORK 天文台的开发和安装

• 批准号: 1459265
• 负责人: Laura Wallace
• 金额: $ 28.77万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459265&HistoricalAwards=false
• 关键词: Collaborative; Research; Unlocking; secrets; slow

The Hikurangi subduction zone offshore the eastern North Island of New Zealand has characteristics that provide a globally unique window into a fundamental aspect of how stress builds up and is relieved as an oceanic plate thrusts (or ?subducts?) beneath continental crust. Recently, seismologists have recognized that subduction megathrust faults undergo slip in episodic ?slow slip events?. Prior to the discovery of slow slip events in the last decade, our paradigms of fault slip were focused on seismic slip in major earthquakes. Since the discovery of slow slip, most studies have focused on deep (20-40 km depth) slow slip events, but we now realize that shallow slow slip events (5-15 km depth) exist that are much more accessible to near-source investigations. These shallow slow fault slip events are centered beneath the ocean so onshore instruments have not been able to measure how much surface deformation occurs. This study takes advantage of planned International Ocean Discovery Program drilling to install sensors in two boreholes that will measure properties indicative of change in the shallow crust that the episodic fault activity causes. Senior researchers in borehole instrumentation will mentor mid-early career scientists, passing along extensive knowledge of such complex implementation and research. Japanese, New Zealand, and German collaborators will participate with the US investigators in this international study, and local communities will benefit from scientist outreach associated with cruises off New Zealand. This study is being undertaken as a ?community proposal?, whereby all data will be immediately publicly available. The shallowest, well-documented slow slip events on Earth occur at the northern Hikurangi margin, offshore Gisborne, New Zealand, at 5-15 km depth. They recur approximately every 1-2 years, with slip on the plate boundary interface of up to 15-20 cm. The unusually close proximity of the Gisborne slow slip events to the seafloor, the large slow slip event magnitudes (equivalent to an earthquake magnitude Mw ~6.3-6.8), and short recurrence intervals makes this the ideal setting for evaluating the near-source hydrological, geochemical, and thermal response of the offshore subduction margin to large, frequent, well-documented deformation transients. The borehole observatory data will clarify the role that fluid pressures, fluid flow, and temperature play in the occurrence of slow slip events, as well as the influence of slow slip event deformation on fluid and geochemical cycling within the forearc. This project will establish the borehole facility and set-up open data access. Analysis of the first two years of data, recovered by ROV, will evaluate the deformation, hydrological, and geochemical responses near the source of slow slip, as well as document the thermal regime of shallow slow slip. One of the borehole installations will target the region surrounding the shallow portion of the megathrust fault , while sensors in a second borehole will target the over-riding plate ~5 km above the slow slip event source.

新西兰北岛东部近海的Hikurangi俯冲带具有以下特征，即为了解应力如何随着海洋板块冲断层（或？subducts？）在大陆地壳之下近年来，地震学家认识到，俯冲型巨型逆冲断层经历幕式滑动。慢滑事件？在过去十年中发现慢滑动事件之前，我们的断层滑动范例集中在大地震中的地震滑动。自发现慢滑以来，大多数研究都集中在深部（20-40 km深度）的慢滑事件上，但我们现在认识到，浅层慢滑事件（5-15 km深度）的存在更容易接近近源调查。这些浅层缓慢断层滑动事件集中在海洋下方，因此陆上仪器无法测量发生了多少地表变形。这项研究利用了计划中的国际海洋发现计划钻探，在两个钻孔中安装传感器，这些传感器将测量指示断层活动引起的浅层地壳变化的特性。 钻孔仪器的高级研究人员将指导职业生涯中期的科学家，通过沿着这种复杂的实施和研究的广泛知识。日本、新西兰和德国的合作者将与美国研究人员一起参与这项国际研究，当地社区将受益于与新西兰游轮相关的科学家外联活动。这项研究是作为一项？社区提案？所有数据将立即公开。地球上最浅的、有据可查的缓慢滑动事件发生在新西兰吉斯伯恩近海的北方希库朗吉边缘，深度为5-15公里。它们大约每隔1-2年发生一次，在板块边界界面上的滑动可达15-20厘米。吉斯伯恩慢滑事件异常接近海底，大的慢滑事件震级（相当于地震震级Mw ~6.3-6.8），以及短的复发间隔，使其成为评估近海俯冲边缘的近源水文，地球化学和热响应的理想设置，以大，频繁，有充分记录的变形瞬变。钻孔观测数据将阐明流体压力、流体流量和温度在慢滑事件发生中的作用，以及慢滑事件变形对弧前流体和地球化学循环的影响。该项目将建立钻孔设施，并建立开放的数据访问。对前两年的数据进行分析，恢复的缓慢滑动，将评估变形，水文和地球化学反应的源附近，以及文件的浅缓慢滑动的热状态。其中一个钻孔装置的目标将是巨型逆冲断层浅层周围的区域，而第二个钻孔中的传感器将目标对准慢滑事件源上方约5公里处的覆盖板。