Physical properties and reflection character of incoming sediments, Nankai, Japan

日本南海传入沉积物的物理性质和反射特征

• 批准号: NE/L001136/1
• 负责人: Lisa McNeill
• 金额: $ 4.53万
• 依托单位: University of Southampton
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2013
• 资助国家: 英国
• 起止时间: 2013 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FL001136%2F1
• 关键词: Physical; properties; reflection; character; incoming

The largest and most destructive earthquakes on Earth occur at subduction zones, where enormous stresses build up along the plate boundary fault between two convergent tectonic plates. The plate boundary fault defines the partition between sediment that is added to the overriding plate (the accretionary prism) and sediment that is subducted along with the down-going plate. The fault will form preferentially in relatively weak sediments that act to lubricate the sliding plane allowing slip without earthquakes. Further down-dip, the earthquake generating potential of this fault changes, moving from an aseismic (no earthquakes) zone to a seismic or seismogenic (earthquake) zone. The physical properties of the incoming sediments at subduction zones are therefore important in controlling subduction fault formation and the subsequent location and rupture pattern of earthquakes.The majority of ocean drilling at subduction zones focuses on sites over the actively deforming accretionary prism sediments as the seabed is shallower and there are many interesting structural targets. However, the incoming sediments represent one of the major controls on the evolution of the subduction system, controlling the location and strength of the initial plate boundary fault. Due to the inaccessibility of the incoming sediments (often in deep water), it is difficult to obtain samples and measure in situ physical properties. In addition drilling provides points of data where we know there may be considerable variation in sediment properties. Seismic reflection data allow the physical properties of the sediments to be measured by proxy and our interpretations extended well beyond the borehole sites. However this method requires a good calibration between seismic data characteristics and the physical properties determined from sample measurements and logging data. Hole C0012H is located on top of a knoll on the seafloor with relatively shallow water depths. The core-log-seismic correlation at this Site (using data acquired during Expedition 338) together with neighbouring Site C0011 can provide a way to understand variations in the physical properties of the input sediments at the Nankai subduction zone.This project will focus on the Nankai subduction zone, located south of Japan, where the Philippine Sea plate is being subducted beneath the Eurasian plate. The section of the Nankai subduction zone off the Kii Peninsula has been the focus of the NanTroSEIZE project since 2007 with 15 drill sites along the NanTroSEIZE transect and two dedicated 3D seismic volumes. There have been two large plate boundary earthquakes in the last century (Tonankai, 1944 and Nankaido, 1946). The incoming plate at this section of the subduction zone has intermediate relief and the sediments are predominantly hemipelagic (sediments deposited slowly out of the water column) with layers of volcanic sediments and terrestrially-derived sediment layers (turbidites). During the recent IODP Expedition 338, log data were collected at Hole C0012H, located on the knoll. The sonic log data that were collected (seismic wave speed within the sediments) are of particular interest as the wave speed is a function of the physical properties of the sediments and underlying basement rocks. We will use these data to derive and compare the sediment physical properties between the cores, logs and seismic data. Tying the sediment physical properties to seismic reflectivity will allow changes to be mapped where there is no direct sampling from drilling sites. This will provide key information about the physical properties of the incoming sediments at the deformation front and lead to an explanation of the inception of the plate boundary fault.

地球上最大和最具破坏性的地震发生在俯冲带，巨大的应力沿着沿着两个会聚构造板块之间的板块边界断层积聚。板块边界断层确定了沉积物之间的分隔，这些沉积物被添加到上覆板块（增生棱柱）和沉积物被沿着俯冲板块。断层将优先在相对较弱的沉积物中形成，这些沉积物起到润滑滑动面的作用，允许滑动而不发生地震。进一步下倾，该断层的发震潜力发生变化，从一个无震（无地震）带移动到一个地震或孕震（地震）带。因此，俯冲带的沉积物的物理性质对控制俯冲断层的形成以及随后的地震位置和破裂模式非常重要。由于海底较浅，而且有许多有趣的结构目标，因此，俯冲带的大多数海洋钻探都集中在活跃变形的增生棱柱沉积物上。然而，进入的沉积物代表了俯冲系统演化的主要控制因素之一，控制了初始板块边界断层的位置和强度。由于难以接近进入的沉积物（通常在深水中），很难获得样品和测量现场物理特性。此外，钻探提供了我们知道沉积物性质可能存在相当大变化的数据点。地震反射数据允许沉积物的物理性质被测量的代理和我们的解释远远超出了钻孔网站。然而，这种方法需要在地震数据特征与从样品测量和测井数据确定的物理性质之间进行良好的校准。孔C 0012 H位于水深相对较浅的海底小丘顶部。该站点的岩心-测井-地震相关性（使用338号考察期间获得的数据）与邻近站点C 0011的相关性可以提供一种了解南海俯冲带输入沉积物物理性质变化的方法。该项目将重点关注位于日本南部的南海俯冲带，菲律宾海板块正在俯冲到欧亚板块之下。自2007年以来，纪伊半岛外的南海俯冲带部分一直是NantroSEIZE项目的重点，沿着NantroSEIZE断面有15个钻探点沿着，还有两个专用的三维地震体。在过去的世纪中，有两次大的板块边界地震（1944年的托南凯和1946年的南海岛）。俯冲带这一部分的传入板块具有中等起伏，沉积物主要是半远洋的（在水柱外缓慢沉积的沉积物），有火山沉积层和陆源沉积层（浊积岩）。在最近的IODP 338考察期间，在位于小山丘上的C 0012 H孔收集了测井数据。所收集的声波测井数据（沉积物内的地震波速度）特别令人感兴趣，因为波速度是沉积物和下伏基岩的物理性质的函数。我们将使用这些数据来推导和比较岩心、测井和地震数据之间的沉积物物理性质。将沉积物的物理特性与地震反射率联系起来，将能够在没有从钻井现场直接取样的情况下绘制变化图。这将提供有关变形前沿沉积物物理性质的关键信息，并解释板块边界断层的起源。

项目成果

NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2, Expedition 338 Proceedings

NanTroSEIZE 第 3 阶段：NanTroSEIZE 板块边界深立管 2，Expedition 338 会议记录

• 发表时间: 2014
• 作者: Strasser M

Along-strike and down-dip variations in décollement physical properties relative to input parameters

相对于输入参数的解理物理特性的沿走向和下倾变化

• 发表时间: 2013
• 作者: Wilson, D J

Core-log-seismic data integration of the input section and decollement properties from the Nantroseize transect

Nantroseize 横断面输入剖面和拆解特性的岩心-测井-地震数据集成

• 发表时间: 2014
• 作者: Wilson, D

Expedition 338: NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2

探险 338：NanTroSEIZE 第 3 阶段：NanTroSEIZE 板块边界深立管 2

• 发表时间: 2013
• 期刊: UKIODP Newsletter
• 作者: Wilson, D

NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2, Expedition 338 Preliminary Report

NanTroSEIZE 第 3 阶段：NanTroSEIZE 板块边界深立管 2，Expedition 338 初步报告

• 发表时间: 2013
• 作者: Moore G