RAPID: GPS and InSAR Observations in Bolivia and Chile of the Co-seismic and Post-seismic Deformation Associated with the 1 Apr, 2014 Mw 8.2 Pisagua, Chile, Earthquake

2014年3月16日，智利北部俯冲带开始了一系列不同寻常的地震，长达10天的地震群向北迁移？这种模式类似于2011年日本东北发生9.0级地震之前的地震群，那次地震引起了智利的担忧，因为这一巨型断裂带上一次失败是在1877年的8.8级地震中，人们认为它有能力再次引发9级地震。到目前为止，该序列中最大的地震是2014年4月1日智利皮萨瓜8.2级地震。这场大地震造成的地面变形将在地震后很长一段时间内持续存在，并在一段时间内衰变。对震中和震后地表形变的测量可以提供有关该地区地球性质的重要信息，增进对形变过程的了解，并有助于确定发生大余震的高可能性区域。由美国、德国、法国、秘鲁和智利的团体在智利安装的大型密集GPS网络将记录到震中附近的这种形变，但预计更远的玻利维亚将发生显著的形变，玻利维亚是一个仪器非常差的地区。这一快速反应项目将在玻利维亚安装新的全球定位系统网络，从智利和玻利维亚现有的全球定位系统站点收集数据，并分析卫星合成孔径雷达数据，以全面捕获与此次事件相关的地面运动。这些数据将有助于理解智利和其他地方(如卡斯卡迪亚、阿拉斯加和日本)大地震的物理和潜在危害。2014年4月1日，智利皮萨瓜8.2级地震是2014年3月16日在智利北部俯冲带开始的一系列异常地震中最大的一次。根据美国地质勘探局的初步远震和面波反演，智利巨型逆冲带沿250公里的沿走向和约150公里的下倾部分发生滑动，上一次失败是在1877年的8.8级地震中。美国、智利、秘鲁、德国和法国在该地区建立了相对密集的连续运行GPS(CGPS)和测量模式GPS(SGPS)台网，从而在智利北部将很好地观测到近场地震间、同震和震后瞬变信号。然而，在距离主震700公里的地方将有显著的同震和震后瞬变运动，包括玻利维亚的几乎所有高原和至少东部科迪勒拉的大部分地区，以及阿根廷西北部的普纳。测量高原及更远地区的中场和远场同震和震后信号对任何地球动力学建模工作都至关重要。然而，玻利维亚高原的仪器非常差，因此目前不能提供准确的后滑和岩石圈松弛反演所需的观测。作为对2014年4月1日智利皮萨瓜8.2级地震的快速反应，研究小组将：(1)在玻利维亚安装10个新的CGPS站点；(2)重新使用玻利维亚和智利的SGPS站点；(3)从玻利维亚和智利的Putons网络内的5个CGPS站点恢复数据；以及(4)从Radarsat-2和TerraSAR-X获取和分析约100个SAR场景。国际地球科学界将通过联阿援助团设施档案馆立即获得数据。将根据外国空间机构所要求的密码保护限制，通过联安部队设施托管的WinSAR档案，向社区提供合成孔径雷达数据。低延迟的大地测量数据处理可能在确定大余震发生可能性高的地区和减灾工作中至关重要，因为最大的余震(4月3日的7.7级)比预期的要大，这可能表明持续的异常活动，邻近地区被认为保持着巨大的滑动赤字。

An unusual sequence of earthquakes began in the northern Chile subduction zone on March 16, 2014 with a 10-day long swarm of earthquakes that migrated to the north ? a pattern similar to the swarm of earthquakes that presaged the 2011 magnitude 9.0 Tohoku Japan earthquake, which provoked concern in Chile because this megathrust zone last failed in a magnitude 8.8 earthquake in 1877 and is thought capable of producing a magnitude 9 earthquake again. So far, the largest event in the sequence is the April 1, 2014 magnitude 8.2 Pisagua, Chile earthquake. The ground deformation caused by this large earthquake will persist long after the earthquake and decay over a period of years. Measurements of the surface deformation during and after the event can provide important information about the properties of the earth in the region, improve understanding of deformation processes, and aid in determining regions with a high likelihood of producing large aftershocks. Large dense GPS networks installed by U.S., German, French, Peruvian, and Chilean groups in Chile will record this deformation close to the earthquake epicenter but significant deformation is expected farther away in Bolivia, a very poorly instrumented region. This rapid response project will install new GPS networks in Bolivia, collect data from existing GPS sites in Chile and Bolivia, and analyze satellite synthetic aperture radar data in order to fully capture the ground motion associated with this event. These data will contribute to understanding the physics and hazard potential of large megathrust earthquakes in Chile and elsewhere, such as Cascadia, Alaska, and Japan.The April 1, 2014 Mw 8.2 Pisagua, Chile earthquake was the largest event in an unusual sequence of earthquakes, which began in the northern Chile subduction zone on March 16, 2014. Based on the USGS preliminary teleseismic and surface wave inversion, slip occurred along a 250 km along-strike and about 150 km down-dip section of the Chile megathrust that last failed in an M 8.8 earthquake in 1877. U.S., Chilean, Peruvian, German, and the French groups have built relatively dense continuously operating GPS (CGPS) and survey mode GPS (SGPS) station networks in this region, thus the near-field inter-, co- and post-seismic transient signals will be well observed in northern Chile. However, there will be significant co-seismic and post-seismic transient motion up to 700 km from the main event, incorporating nearly all of the Altiplano and at least much of eastern Cordillera in Bolivia, and the Puna of northwestern Argentina. Measuring the mid- and far-field co- and post-seismic signals in the Altiplano and beyond will be critical to any geodynamic modeling effort. The Bolivian Altiplano, nevertheless, is very poorly instrumented and so cannot, at present, provide the observations required for accurate inversions of afterslip and lithospheric relaxation. In rapid response to the April 1, 2014 Mw 8.2 Pisagua, Chile earthquake, the research team will: (1) install 10 new CGPS stations in Bolivia; (2) reoccupy SGPS sites in Bolivia and Chile; (3) retrieve data from 5 CGPS stations within the PLUTONS network in Bolivia and Chile; and (4) acquire and analyze about 100 SAR scenes from Radarsat-2 and TerraSAR-X. Data will be made immediately available to the international earth science community through the UNAVCO Facility Archive. SAR data will be tasked and made available to the community with the password-protected restrictions required by the foreign space agencies through the WinSAR archive hosted by the UNAVCO Facility. Low latency geodetic data processing could be critical in determining regions with a high likelihood of producing large aftershocks and for hazard mitigation efforts because the largest aftershock (M 7.7 on April 3) was larger than expected, potentially indicating continued unusual activity with the neighboring segments thought to retain a large slip deficit.