Core to regional scale synthesis of fault zone properties and fluids at subduction zones: Drivers of seismogenic behaviour

俯冲带断层带性质和流体的区域尺度综合的核心：孕震行为的驱动因素

• 批准号: NE/I006184/1
• 负责人: Lisa McNeill
• 金额: $ 30.62万
• 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: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI006184%2F1
• 关键词: Core; regional; scale; synthesis; fault

Most of the world's large earthquakes happen on the plate boundary faults at subduction zones where two plates converge (e.g. Sumatra in 2004, 2005, and 2007; Chile in 2010). Because the parts of these faults that move during the earthquake lie underwater, they can also be the source of major tsunami. However, different subduction zones are subject to different sizes of earthquakes, and different patterns of earthquake rupture, so that the hazards vary significantly. In most cases rupture on the plate boundary faults is limited to a zone where the fault lies from ~30-40km up to ~5-15km beneath the seabed, but in some cases the fault rupture is thought to have been much more extensive and potentially to have reached the seabed. In other cases the faults are sometimes seen to move more gradually, without an earthquake. In other cases (e.g., Nankai margin offshore Japan), movement on the main plate boundary fault is affected by faults within the accretionary prism, that forms as sediment is scraped off the downgoing plate, and these faults may slip affecting the size of the tsunami waves generated. A final major problem with knowing these hazards at a given subduction zone is that the biggest earthquakes normally only occur every few hundred years, so that our records of the effects are very incomplete. These different fault behaviours depend on the physical properties of the faults themselves, controlled by the seabed sediments adjacent to the subduction zone, and factors such as the presence of fluids within the fault. One way to determine these properties, and presence of fluids, is to drill into the fault zone and directly take samples or measurements of the rock properties using 'logging' technology; this has been done in several places round the world, but even with the most modern technology (riser drilling), it is only possible in the shallower parts of faults, and generates a set of observations effectively at a single location. Drilling at a number of different places on subduction zones together with associated seismic experiments (that bounce sound waves off structures within the earth) show that these properties are very variable, within a single region, and between regions. This reinforces that the combination of drilling (providing local detailed information) and seismic data (providing regional information) should be the primary method for assessing fault properties and their hazard potential: the technique employed in this project. We aim to better understand the behaviour of subduction zone faults by combining seismic and drilling data from several subduction zones around the world. We have chosen regions which have contrasting thicknesses of sediments, and where known fault activity and type and size of resulting earthquakes vary. We will use the drilling data to increase our ability to interpret the properties and fluid content of the fault zones from seismic data at the same location. Then using the seismic interpretations to extend our knowledge of the fault zones over much broader regions, we will investigate variations both down and along the plate boundary fault. We will use the same methods to investigate the relationship between the main plate boundary fault and smaller faults within the accretionary prism. We will then extend our analysis to regions where seismic data have been collected, but which have not yet been drilled, including margins offshore Sumatra and New Zealand. The results generated by the project will allow drilling on these new margins (Sumatra and New Zealand) to be targeted more effectively, thus obtaining new samples and measurements from the sections of these subduction systems with greatest significance for earthquake generation. Ultimately we will relate the interpretations of the state of the plate boundary faults to the known earthquake behaviour and tsunami history, aiming to improve assessments of the hazards at other locations where the long-term behaviour is not known.

世界上大多数大地震都发生在两个板块交汇的俯冲带的板块边界断层上（例如2004年，2005年和2007年的苏门答腊; 2010年的智利）。由于这些断层在地震中移动的部分位于水下，它们也可能是大海啸的来源。然而，不同的俯冲带所遭受的地震规模不同，地震破裂的模式也不同，因此地震的危害也有很大差异。在大多数情况下，板块边界断层上的断裂仅限于海底以下约30- 40公里至约5- 15公里的区域，但在某些情况下，断层断裂被认为更广泛，并可能到达海底。在其他情况下，有时可以看到断层移动得更缓慢，没有地震。在其他情况下（例如，在南海边缘（日本近海），主板块边界断层的运动受到增生棱柱内断层的影响，增生棱柱是在沉积物从下行板块上刮下来时形成的，这些断层可能会滑动，影响所产生的海啸波的大小。在已知的俯冲带中，最后一个主要问题是，最大的地震通常每隔几百年才发生一次，因此我们对地震影响的记录非常不完整。这些不同的断层行为取决于断层本身的物理性质，这些物理性质受俯冲带附近海底沉积物的控制，以及断层内是否存在流体等因素。确定这些属性和流体存在的一种方法是钻入断层带，并使用“测井”技术直接采集岩石属性的样本或测量值;这已经在世界各地的几个地方完成，但即使使用最现代的技术（立管钻井），也只能在断层的较浅部分进行，并在单个位置有效地生成一组观测结果。在俯冲带的许多不同地方进行的钻探以及相关的地震实验（将声波从地球内部的结构上反射回来）表明，这些特性在单个区域内以及区域之间都是非常可变的。这进一步表明，钻井（提供当地详细信息）和地震数据（提供区域信息）相结合，应是评估断层特性及其潜在危害的主要方法：本项目采用的技术。我们的目标是通过结合世界各地几个俯冲带的地震和钻井数据，更好地了解俯冲带断层的行为。我们选择的地区具有不同厚度的沉积物，已知的断层活动和地震类型和规模各不相同。我们将利用钻井数据提高我们从同一地点的地震数据解释断层带的性质和流体含量的能力。然后利用地震解释将我们对断裂带的认识扩展到更广泛的区域，我们将调查板块边界断层的向下和沿沿着的变化。我们将用同样的方法来研究主板块边界断层和增生棱柱体内部较小断层之间的关系。然后，我们将把我们的分析扩展到已经收集了地震数据但尚未钻探的地区，包括苏门答腊和新西兰近海的边缘。该项目产生的结果将使这些新的边缘（苏门答腊和新西兰）的钻探更有效地成为目标，从而从这些俯冲系统的部分获得新的样本和测量结果，对地震的发生具有最大的意义。最终，我们将解释板块边界断层的状态与已知的地震行为和海啸历史，旨在改善对长期行为未知的其他地点的危害评估。

项目成果

Downgoing plate topography stopped rupture in the A.D. 2005 Sumatra earthquake

公元 2005 年苏门答腊岛地震中，下降的板块地形阻止了破裂

• DOI: 10.1130/g37258.1
• 发表时间: 2016
• 期刊: Geology
• 影响因子: 5.8
• 作者: Henstock T

Pervasive deformation of an oceanic plate and relationship to large >Mw 8 intraplate earthquakes: The northern Wharton Basin, Indian Ocean

• DOI: 10.1130/g36446.1
• 发表时间: 2015-04
• 期刊: Geology
• 影响因子: 5.8
• 作者: J. Geersen;J. Bull;L. McNeill;T. Henstock;C. Gaedicke;N. Chamot‐Rooke;M. Delescluse

The 2004 Aceh-Andaman Earthquake: Early clay dehydration controls shallow seismic rupture

2004 年亚齐-安达曼地震：早期粘土脱水控制浅层地震破裂

• DOI: 10.1002/ggge.20193
• 发表时间: 2013
• 期刊: Geochemistry, Geophysics, Geosystems
• 作者: Geersen J

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

Updip rupture of the 2004 Sumatra earthquake extended by thick indurated sediments

2004 年苏门答腊地震的上倾破裂被厚厚的硬质沉积物扩展

• DOI: 10.1038/ngeo1176
• 发表时间: 2011
• 期刊: Nature Geoscience
• 影响因子: 18.3
• 作者: Gulick S