RAPID: Investigation of Co-seismic Surface Cracks Produced during the April 1, 2014, Magnitude 8.2 Pisagua, Chile, Earthquake

RAPID：调查 2014 年 4 月 1 日智利皮萨瓜 8.2 级地震期间产生的同震表面裂缝

• 批准号: 1443410
• 负责人: Richard Allmendinger
• 金额: $ 2.48万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-01 至 2016-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1443410&HistoricalAwards=false
• 关键词: RAPID; Investigation; Co; seismic; Surface

Surface cracks, if preserved, formed during large subduction zone earthquakes potentially provide records of past large earthquakes. However, these subtle surface features disappear within days in most settings. Due to the aridity of the Atacama Desert in Chile, these cracks are preserved and can be used to estimate deformation associated with large earthquakes along the Chilean subduction zone. The recent magnitude 8.2 earthquake in Chile affords an opportunity to directly test the idea that cracks form during these large events and that the cracks can be used to estimate the amount of slip that occurred during an earthquake and the amount of deformation experienced above the earthquake source region. If successful, the project would add a new method to improve understanding of earthquake hazards associated with large megathrust earthquakes in Chile and elsewhere, such as Cascadia, Alaska, and Japan.The goal of this RAPID project, carried out in collaboration with Chilean researchers, is to collect scan line data of co-seismic Mode I surface cracks in the Chilean Coastal Cordillera produced by the April 1, 2014 Mw 8.2 Pisagua earthquake. Cracks commonly form in unconsolidated deposits and must be measured within about six months from the time of the earthquake in order to be identified as having been produced during the earthquake. Accurate measurement of crack apertures is likewise important for determination of surface strain for comparison with GPS data that will be forthcoming from this event. As the walls of the cracks degrade over time, accurate measurement of aperture becomes more and more difficult. The objectives are to re-measure scan lines that have already been measured, pre-earthquake, at Punta de Lobos and to measure new scan line data for at least three separate sites in the region between the city of Iquique and north of the pueblo of Pisagua. Initial InSAR data suggest that the highest surface deformation will be encountered between Iquique and Pisagua. Co-seismic surface cracks provide a unique long term record of thousands of cycles of plate boundary seismicity. The Pisagua earthquake provides an outstanding opportunity to document the crack population developed during a single earthquake to help refine models of co-seismic crack generation as well as explore the basic question of how much of the co-seismic geodetic signal (predominantly GPS) reflects recoverable elastic deformation and non-recoverable plastic deformation. These data will help refine models of co-seismic surface deformation and average rupture segments, which are key inputs into seismic hazard assessment.

在大俯冲带地震期间形成的表面裂纹可能会提供过去的大地震记录。但是，这些微妙的表面特征在大多数情况下几天内消失了。由于智利阿塔卡马沙漠的干旱，保留了这些裂缝，可用于估计与智利俯冲带大地震相关的变形。智利最近的8.2级地震提供了一个机会，可以直接测试这些大事件中裂纹形成的想法，并且可以使用裂缝来估计地震期间发生的滑移量以及地震源区域上方经历的变形量。如果成功的话，该项目将增加一种新方法来提高对与智利和其他地方的大型大型地震相关的地震危害的了解地震。裂纹通常以非固定的沉积物形式形成，必须在地震后大约六个月内测量，以确定地震期间产生的裂纹。精确测量裂纹孔径对于确定表面应变以与该事件将要进行的GPS数据进行比较也很重要。随着裂缝的壁随时间变化的降解，准确的孔径测量变得越来越困难。这些目的是重新测量扫描线，这些扫描线在Punta de Lobos上已经测量，地球前，并测量Iquique市和Pisagua Pueblo以北的该地区至少三个独立地点的新扫描线数据。初始INS INAR数据表明，Iquique和Pisagua之间将遇到最高的表面变形。共同的表面裂纹提供了数千个板块边界地震性周期的独特长期记录。 Pisagua地震提供了一个很棒的机会，可以记录单个地震期间开发的裂纹种群，以帮助完善共同的裂纹产生模型，并探讨了有多少共同震荡的大地测量信号（主要是GPS）反映了可回收的弹性变形和不可恢复的塑性塑性变形。这些数据将有助于完善共同的表面变形和平均破裂段的模型，这是对地震危害评估的关键输入。