RAPID: Recording Fault-Zone Trapped Waves from Aftershocks of the M6.3 Christchurch Earthquake Sequence in New Zealand to Document the Subsurface Damage Zones

RAPID：记录新西兰 M6.3 基督城地震序列余震中的断层带陷波，以记录地下受损区域

• 批准号: 1137632
• 负责人: Yong-Gang Li
• 金额: $ 2.11万
• 依托单位: University of Southern California
• 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: 2011-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1137632&HistoricalAwards=false
• 关键词: RAPID; Recording; Fault; Zone; Trapped

The M6.3 Christchurch earthquake struck the Canterbury region in New Zealand's South Island on 22February 2011, causing widespread damage and multiple fatalities. The earthquake occurred at 5 kmdepth, 10 km south-east of Christchurch, New Zealand's 2nd-most populous city. It followed ~6 monthsafter the Sept. 4, 2010 M7.1 Darfield earthquake in the same region. The Christchurch earthquake waspart of a series of earthquakes and aftershocks in the region following the 2010 M7.1 Darfield. NewZealand's GNS Science describe it as "technically an aftershock" of the earlier event while otherseismologists from USA and Australia consider it a separate event, given its location on a separate faultsystem. Seismologically, this M6.3 quake is classed as an aftershock because of its relationship to theongoing activity since September last year. However, it has generated a significant series of its ownaftershocks, many of which are considered big for a M6.3 earthquake. Over 200 aftershocks including aM5.7 were experienced in the first week. It did not occur on the Greendale Fault, on which the 2010 M7.1Darfield quake occurred, but on a previously unknown blind fault line running 17 km east-west south ofChristchurch, at depths of 3?12 km. On the contrary, precise aftershock relocations suggest that at leasttwo north-east/south-west trending faults lie between the two and that there is no evidence from theearthquake data of an extension of the Greendale Fault. However, there are still many aftershocks of the2010 M7.1 Darfield earthquake spread along the fault line of the 2011 M6.3 Christchurch earthquake.In order to document the complicated subsurface structure of the damage zones caused by thesequence of the 2010 M7.1 Darfield and the 2011 M6.3 Christchurch earthquakes in the Canterburyregion of NZ?s South Island, the investigator proposes to record fault-zone trapped waves (FZTWs) generated byaftershocks, and use the FZTWs to image the rupture zones composed by damaged fault rocks atseismogenic depths. Because the amplitude and dispersive feature of FZTWs are sensitive to thegeometry and physical properties, and the location of aftershocks (within or outside) of the low-velocityfault-zone waveguide formed by severely damaged rocks in these two earthquakes, observations andnumerical modeling of recorded FZTWs allow us to learn more about (1) the width, velocity reduction, Qvalue and depth extension of damage zones of the 2010 M7.2 and 2011 M6.3 earthquakes, (2) the shapeof subsurface rupture zones with the principal slip plans of the mainshocks, and if the two rupturesegments are connected at seismogenic depths, (3) the difference in rock damage magnitude caused bythese two earthquakes occurring at different depths with different sizes, (4) the fault healing with timeafter the mainshock.This RAMP experiment will be collaborated by USC/UoA /UoC/GNS in NZ to pursue the value ofthe work proposed, likewise with the ongoing efforts by the NZ national GEONET seismic network andresearchers. GNS will offer to follow the USC/UoA/UoC work and help them keep up with otherinitiatives and projects concerning the Darfield event.

2011年2月22日，新西兰南岛坎特伯雷地区发生基督城6.3级地震，造成大面积破坏和多人死亡。地震发生在新西兰第二大人口城市基督城东南10公里处，震源深度5公里。它遵循了9月后6个月。4、2010年同一地区发生达菲尔德7.1级地震。基督城地震是2010年达菲尔德M7.1地震后该地区一系列地震和余震的一部分。新西兰的GNS科学将其描述为“技术上的余震”，而来自美国和澳大利亚的其他地震学家则认为这是一个单独的事件，因为它位于一个单独的断层系统上。从地震学上讲，这次6.3级地震被归类为余震，因为它与去年9月以来的持续活动有关。然而，它已经产生了一系列重要的余震，其中许多被认为是6.3级地震的大地震。第一周内发生了包括aM5.7在内的200多次余震。它并没有发生在2010年发生M7.1达菲尔德地震的格林德尔断层上，而是发生在基督城以南东西走向17公里、深度为3？12公里。相反，精确的余震重新定位表明，至少有两个东北/西南走向的断层位于两者之间，并没有证据从地震数据的格林德尔断层的延伸。然而，2010年达菲尔德7.1级地震的余震仍然沿着2011年克赖斯特彻奇6.3级地震的断层线传播。在南岛，研究者提出记录余震产生的断层带陷波（FZTW），并利用FZTW成像孕震深度处由受损断层岩组成的破裂带。由于FZTW的振幅和频散特性对地震的几何、物理性质和余震位置非常敏感通过对这两次地震中严重破坏的岩石所形成的低速断层带波导的观测和数值模拟，我们可以更多地了解（1）宽度，速度降低，2010年7.2级和2011年6.3级地震破坏带的Q值和深度延伸;（2）地下破裂带的形状与主震的主滑动面，以及两个破裂段是否在孕震深度连接，（3）这两次地震发生在不同深度和不同规模的地震所造成的岩石破坏程度的差异，（4）主震后断层随时间愈合。同样，新西兰国家GEONET地震网络和研究人员正在进行的努力也是如此。GNS将提供跟踪USC/UOA/UOC的工作，并帮助他们跟上有关达菲尔德事件的其他倡议和项目。