Seismic Documentation of Subsurface Damage Zones of the M7.2 Darfield and M6.3 Christchurch Earthquake Sequence in New Zealand Using Fault-Zone Trapped Waves

使用断层带陷波记录新西兰 M7.2 达菲尔德和 M6.3 基督城地震序列的地下损坏区

• 批准号: 1142071
• 负责人: Yong-Gang Li
• 金额: $ 21.53万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Continuing 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=1142071&HistoricalAwards=false
• 关键词: Seismic; Documentation; Subsurface; Damage; Zones

The M6.3 Christchurch earthquake struck the Canterbury region in New Zealand's South Island on 22 February 2011, following ~6 months after the September 4, 2010 M7.1 Darfield earthquake in the same region, and has generated a significant series of aftershocks, many of which are considered big for a M6.3 earthquake. It is not known whether the later M6.3 event is technically an aftershock because of relationship to the ongoing activity since September last year, or it is a separate event, given its location on a separate blind fault south of Christchurch. In order to study the complicated subsurface structure of damage zones caused by this sequence of earthquakes in NZ, under the support of an NSF-RAPID and with collaboration of New Zealand researchers, the investigators deployed 2 short linear seismic arrays of 12 PASSCAL seismographs across the Greendale fault that ruptured in the 2010 M7.1 Darfield earthquake and the aftershock zone of the 2011 M6.3 Christchurch earthquake. Two arrays worked for 4 months starting from May 5th, 2011 and recorded ~1,000 M2 aftershocks, including a M6.0 and five M5+ large aftershocks with clustered events. In this project the PI will conduct a systematic examination of the waveform data recorded at the two cross-fault arrays to identify fault-zone trapped waves (FZTWs) generated by aftershocks, and simulate these FZTWs using a 3-D finite-difference code to document (1) the subsurface structure and material properties (width, depth extension, velocity reduction, Q value and co-seismic rock damage magnitude) of fault zones ruptured in Darfield and Christchurch earthquakes, (2) the rupture segmentation and branching at seismogenic depth, (3) the post-mainshock heal of fault rocks from repeated aftershocks, and (4) compare the results from this study with those we have obtained at rupture zones of California earthquakes. With a comparison of major earthquakes at active faults on the plate boundaries in NZ and CA, the most basic information on the in-situ state of the fault zone will aid further understanding of earthquake processes and hazards globally. Results of subsurface rupture segmentation and/or connection of the Darfield and Christchurch earthquakes will help to address the question if the second event is the first one?s aftershock or an individual mainshock, and evaluate the possibility of a future earthquake in Christchurch areas.

新西兰南岛坎特伯雷地区于 2010 年 9 月 4 日发生 M7.1 级达菲尔德地震约 6 个月后，于 2011 年 2 月 22 日袭击了新西兰南岛坎特伯雷地区，发生了 M6.3 级地震，并引发了一系列严重的余震。其中对于M6.3地震来说被认为是大地震。目前尚不清楚后来的 M6.3 事件在技术上是否是一次余震，因为与去年 9 月以来正在进行的活动有关，或者它是一个单独的事件，因为它位于基督城以南的一个单独的盲断层上。为了研究新西兰这一系列地震造成的受损区复杂的地下结构，在 NSF-RAPID 的支持下并与新西兰研究人员合作，研究人员在整个新西兰部署了 2 个由 12 台 PASSCAL 地震仪组成的短线性地震阵列。在2010年达菲尔德M7.1地震和2011年基督城M6.3地震余震区中破裂的格林代尔断层。两个阵列自2011年5月5日起工作了4个月，记录了约1000次M2余震，其中包括一次M6.0和5次M5+大型余震，且具有聚集性事件。在该项目中，PI将对两个跨断层阵列记录的波形数据进行系统检查，以识别余震产生的断层带陷波（FZTW），并使用3D有限差分代码模拟这些FZTW文件 (1) 达菲尔德地震和基督城地震中破裂的断层带的地下结构和材料特性（宽度、深度延伸、速度减小、Q 值和同震岩石破坏程度），(2)地震发生深度的破裂分段和分支，（3）反复余震造成的断层岩石的主震后愈合，以及（4）将本研究的结果与我们在加利福尼亚地震破裂带获得的结果进行比较。通过比较新西兰和加拿大板块边界活动断层的大地震，了解断层带原位状态的最基本信息将有助于进一步了解全球地震过程和灾害。达菲尔德地震和基督城地震的地下破裂分段和/或联系的结果将有助于解决第二次事件是第一次余震还是单个主震的问题，并评估基督城地区未来发生地震的可能性。