Observations of a newly discovered fault: Tomography, locations and source mechanisms for aftershocks of the M7.1 Darfield, New Zealand earthquake

对新发现断层的观测：新西兰达菲尔德 M7.1 地震余震的断层扫描、位置和震源机制

• 批准号: 1141983
• 负责人: Clifford Thurber
• 金额: $ 11.73万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-01-01 至 2014-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1141983&HistoricalAwards=false
• 关键词: Observations; newly; discovered; fault; Tomography

The Mw7.1 September 4, 2010 Darfield earthquake and the subsequent Mw6.3 February 22, 2011 Christchurch earthquake were the most damaging earthquakes in New Zealand since the 1931 Hawke?s Bay earthquake. The latter event caused enormous damage throughout Christchurch, New Zealand?s second largest city. These earthquakes occurred on previously unmapped faults in the eastern South Island. The behavior of this earthquake sequence has led to many questions about the fundamental characteristics of the fault on which they occurred and the local geology and tectonics.Five Victoria University of Wellington seismometers and nine PASSCAL seismometers were installed in the region surrounding the surface rupture of the Darfield earthquake within two weeks of its occurrence and were removed in mid January 2011. Using data recorded at these temporary stations and additional permanent regional stations, the researchers will study the aftershocks of the Darfield earthquake in order to investigate the seismically active fault structure, the temporal evolution of aftershocks and fault activity, and the regional seismic structure. A relocated aftershock catalog will be developed based on the GeoNet catalog for New Zealand. The investigators will examine how seismicity evolved throughout the fault system, with a focus on faults that had been identified beneath Christchurch prior to the February 2011 earthquake. The algorithm tomoDD will also be used to simultaneously solve for P- and S-wave velocities in the region surrounding the fault rupture. The benefit of this will be two-fold: the improved 3D velocity model will result in improved aftershock locations and it will constrain the local subsurface structure. For example, a velocity contrast across the fault could be used to constrain its age, which is currently a topic of controversy.Focal mechanisms will be calculated for aftershocks.In conjunction with aftershock locations, focal mechanisms will allow the researchers to constrain the directions of motion along the various fault segments that have been active in the aftershock sequence. By searching for repeating earthquakes and non-volcanic tremor, they will be able to explore the variety of ways in which the faults associated with the Darfield earthquake move. Repeating earthquakes may be caused by a section of fault that is experiencing aseismic creep, either before or after a large earthquake. By studying the first four months of the aftershock sequence of the 2010 Darfield earthquake, they will help establish the fault structure of previously unknown fault segments, understand the evolution of activity along them, and understand the factors that contributed to the more devastating 2011 Christchurch earthquake.

MW7.1 2010年9月4日，达菲尔德地震和随后的MW6.3 2011年2月22日，基督城地震是自1931年霍克（Hawke）霍克（Hawke）海湾地震以来新西兰最具破坏性的地震。后一个事件在新西兰第二大城市造成了巨大的破坏。这些地震发生在南部岛东部的以前未塑造的断层上。这次地震序列的行为导致了许多问题，有关它们发生的故障的基本特征以及当地的地质和构造学的基本特征。惠灵顿维多利亚大学地震仪和九个密封地震仪以及围绕达菲尔德（Darfield）段落的临时记录的临时置于2011年中期的临时置于临时的暂时性的地区。站点，研究人员将研究达菲尔德地震的余震，以研究地震活跃的断层结构，余震的时间演变和断层活动以及区域地震结构。将根据新西兰的Geonet目录开发重新定位的余震目录。调查人员将检查地震性如何在整个断层系统中演变，重点是在2011年2月地震之前确定的基督城下方的断层。 TomoDD算法也将用于同时求解断层破裂区域中的P和S波速度。这将是两个方面的好处：改进的3D速度模型将改善余震位置，并限制局部地下结构。例如，整个断层之间的速度对比度可以用于限制其年龄，这是当前的争议主题。将计算出余震的焦点机制。与余震位置结合使用，焦点机制将允许研究人员限制在余波序列中活跃的各种断层段的方向。通过寻找重复地震和非沃尔底克震颤，他们将能够探索与达菲尔德地震移动相关的断层的多种方式。重复地震可能是由于一部分发生在大地震之前或之后经历无性蠕动的断层引起的。通过研究2010年Darfield地震的余震序列的前四个月，它们将有助于建立以前未知的断层段的断层结构，了解沿它们沿线的活动的演变，并了解导致2011年更具破坏性的基督教地震的因素。