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

2010年9月4日达菲尔德地震和随后的2011年2月22日基督城地震是新西兰自1931年霍克？海湾地震。后一个事件造成了巨大的损害整个基督城，新西兰？的第二大城市。这些地震发生在南岛东部以前未绘制的断层上。这一地震序列的行为导致了许多关于断层的基本特征以及当地地质和构造的问题。达菲尔德地震发生后两周内，惠灵顿大学维多利亚大学的五台地震仪和九台PASSCAL地震仪被安装在地面破裂周围的区域，并于2011年1月中旬被拆除。利用这些临时台站和其他永久性区域台站记录的数据，研究人员将研究达菲尔德地震的余震，以调查地震活动断层结构、余震和断层活动的时间演变以及区域地震结构。将根据新西兰GeoNet目录编制重新定位的余震目录。调查人员将研究地震活动如何在整个断层系统中演变，重点是2011年2月地震前在基督城下方发现的断层。算法tomoDD也将被用来同时解决的P-和S-波速度在该地区周围的断层破裂。这样做的好处是双重的：改进的三维速度模型将导致改善余震的位置，它将限制当地的地下结构。例如，断层上的速度差可以用来限制其年龄，这是目前一个有争议的话题。将计算余震的震源机制。结合余震的位置，震源机制将允许研究人员限制沿着余震序列中活跃的各个断层段的运动方向。通过寻找重复地震和非火山震颤，他们将能够探索与达菲尔德地震相关的断层移动的各种方式。重复的地震可能是由一段断层在大地震之前或之后经历的地震蠕动引起的。通过研究2010年达菲尔德地震余震序列的前四个月，他们将有助于建立以前未知的断层段的断层结构，了解活动沿着它们的演变，并了解造成更具破坏性的2011年基督城地震的因素。

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.