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，智利北方俯冲带发生了一系列不寻常的地震，一系列长达10天的地震向北迁移。这一模式类似于2011年日本东北部9.0级地震的前兆地震群，这引起了智利的关注，因为这一巨型逆冲带上次在1877年发生8.8级地震时失败，并被认为能够再次产生9级地震。到目前为止，该序列中最大的事件是2014年4月1日智利皮萨瓜8.2级地震。这次大地震引起的地面变形将在地震后很长时间内持续存在，并在数年内衰减。在地震发生期间和之后对地表变形的测量可以提供有关该地区地球性质的重要信息，提高对变形过程的理解，并有助于确定产生大余震的可能性很高的地区。美国安装的大型密集GPS网络，在智利的德国、法国、秘鲁和智利小组将在靠近震中的地方记录到这种变形，但预计在更远的玻利维亚，一个仪器设备非常差的地区，也会有显著的变形。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，以便充分捕捉与这一事件有关的地面运动。2014年4月1日智利皮萨瓜地震是智利北方俯冲带发生的一系列异常地震中规模最大的一次，这一系列异常地震发生在2014年3月16日智利北部俯冲带。根据美国地质勘探局的初步地震勘探和面波反演，滑动发生在智利巨型逆冲断层的一个沿走向沿着约250 km和下倾约150 km的部分，该断层最后一次在1877年的8.8级地震中失败。美国，智利、秘鲁、德国和法国等国的GPS观测组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）台站网，因此，智利北方将能很好地观测到震间、同震和震后的近场瞬变信号。然而，将有显着的同震和震后瞬态运动，从主事件，包括几乎所有的高原和至少大部分东部科迪勒拉在玻利维亚，和阿根廷西北部的普纳700公里。测量高原及以外地区的中、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，是非常糟糕的仪器，所以不能，目前，提供所需的观测准确反演后滑和岩石圈松弛。为了快速应对2014年4月1日智利皮萨瓜8.2级地震，研究小组将：（1）在玻利维亚安装10个新的CGPS站;（2）重新使用玻利维亚和智利的SGPS站;（3）从玻利维亚和智利的PLUTONS网络内的5个CGPS站检索数据;（4）从雷达卫星2号和TerraSAR-X获取并分析约100个SAR场景。数据将通过联合国志愿人员组织设施档案立即提供给国际地球科学界。搜索和救援数据将通过由联合国航空航天事务办公室设施托管的WinSAR档案，在外国空间机构所要求的密码保护限制下分配并提供给社区。低延迟大地测量数据处理在确定产生大余震的可能性很高的地区和减灾工作中可能是至关重要的，因为最大的余震（4月3日的M7.7）比预期的要大，可能表明持续的不寻常活动，相邻的部分被认为保留了很大的滑动赤字。

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.