RAPID: Collaborative: April 16, 2016 Mw 7.8 Pedernales Earthquake, Ecuador: The Role of Asperities in Rupture Propagation, Aftershock Sequences, and Post Seismic Deformation

2016年4月16日，厄瓜多尔俯冲带发生了里氏7.8级地震。这次地震对这个国家来说是毁灭性的，造成660人死亡，12000人受伤，30亿美元的财产损失。由于厄瓜多尔是一个经济陷入困境的发展中国家，这种个人和经济损失被放大了。来自国际网络的初步地震数据表明，4月16日的地震沿南美板块和纳斯卡板块之间的界面从北向南破裂。由加拉帕戈斯群岛热点的痕迹形成的山脊位于断裂末端的南部，可能限制了地震的范围。这是推动这一提议的主要假设之一，这也将有助于确定2016年地震与1942年发生在附近的7.8级地震之间的关系。在4月16日地震前后，除了测量现有的GPS纪念碑外，还将在该地区部署20个宽带地震仪和5个连续GPS仪器。这些地震和GPS部署旨在补充厄瓜多尔现有的国家网络，详细绘制余震序列，并评估俯冲带各段之间的应力传递。加拉帕戈斯群岛热点轨道以南的地区最近没有破裂，但大地测量数据表明这一段是锁定的。因为它更靠近人口密集的瓜亚基尔，这个封闭的部分增加了地震的危险。2016年4月16日，厄瓜多尔佩德纳莱斯附近的哥伦比亚-厄瓜多尔海沟发生里氏7.8级地震。这次地震代表了纳斯卡-南美板块边缘自1942年和1958年最后一次破裂以来积累的应变的释放。初步数据表明，Mw7.8地震破坏了与1942年Mw7.8地震相同的板块界面。Pedernales地震提供了一个机会，可以利用最先进的技术，在地震周期的各个阶段（地震间、地震同震和地震后）测量板块界面上的滑动历史，并研究岩石在集中应力、分割破裂、促进和/或抑制破裂传播方面的作用，以及慢滑事件的作用。在地震周期中。这次与Escuela Politecnica national （Instituto geoofisico， IG）和Instituto Geografico Military （IGM）的合作将通过以下方式调查与这次破坏性事件相关的地震前后变形：1)部署宽带地震阵列来记录余震；2)现有eGPS站点的观测；3)在站点密度低但余震信号潜力大的地区新建5个cGPS台站。纳斯卡板块俯冲到南美板块和/或北安第斯地块之下。沿哥伦比亚-厄瓜多尔海沟，产生7.5级地震。1906年的8.8级地震使从厄瓜多尔中部到哥伦比亚中部的大部分板块边界破裂。2016年4月16日发生的里氏7.8级地震位于1906&amp；#8232；事件，似乎与1942年的事件有重叠。佩德纳莱斯地震提供了一个机会来检验这样一个假设，即大地震到大地震的陡度是持续存在的。多个旋回，并研究岩石在阻止沿走向滑动中的作用&amp；#8232；以及锁定部分和爬行部分之间的关系。组合后的GPS&amp；#8232；地震数据将提供：1)高精度的余震位置和震源机制；以及它们与板间破裂带和相邻段的关系；2)详细结构&amp；#8232；Pedernales断裂区；3)地震后变形场表征，&#8232；包括后滑和粘弹性松弛，量化同震和震后应力传递；4)低频和/或慢滑余震和/或非火山余震的识别；地震，以及慢滑事件在地震周期中的作用；5)识别时间&amp；#8232；可能反映断裂带愈合或其他随时间变化的材料特性的变化变化在破裂区；6)描述现场放大效应和后果的信息&amp；#8232；变量风险。

A Mw 7.8 earthquake occurred along the Ecuadorian subduction zone on April 16, 2016. This earthquake was devastating to the country, causing 660 fatalities 12,000 injuries, and $3B in property damage. This personal and economic toll is amplified because Ecuador is a developing country, with a troubled economy. Preliminary seismic data from international networks indicate that the April 16 earthquake ruptured from north to south along the interface between the South American and Nazca plates. The ridge formed by the trace of the Galapagos hotspot lies just to the south of the end of the rupture and may have limited the extent of the earthquake. This is one of the principal hypotheses driving this proposal, which will also help determine the relationship between the 2016 earthquake and the Mw 7.8 earthquake that occurred nearby in 1942. Twenty broadband seismometers and 5 continuous GPS instruments will be deployed in the region around the April 16th earthquake, in addition to surveying existing GPS monuments. These seismic and GPS deployments are designed to complement the existing national Ecuadorian network, to map the aftershock sequence in great detail, and evaluate stress transfer between segments of the subduction zone. The area to the south of the Galapagos hotspot track has not ruptured in recent times, but geodetic data indicate that this section is locked. Because it is closer to a large population center, Guayaquil, this locked segment poses an increased seismic hazard.On April 16th, 2016 a Mw7.8 earthquake struck along the Colombia-Ecuador trench near Pedernales, Ecuador. This earthquake represents the release of accumulated strain along the Nazca-South American plate margin since its last ruptures in 1942 and 1958. Initial data suggest that the Mw7.8 earthquake ruptured the same part of the plate interface as the Mw7.8 1942 earthquake. The Pedernales earthquake offers an opportunity to use state of the art technologies to measure the history of slip on the plate interface over the phases of the earthquake cycle: interseismic, coseismic, and postseismic and to study the role of asperities in focusing stress, segmenting ruptures, promoting and/or inhibiting rupture propagation, and the role of slow slip events
in the earthquake cycle. This collaboration with the Escuela Politecnica Nacional (Instituto Geofisico, IG) and Instituto Geografico Military (IGM) shall investigate the co- and post-seismic deformation associated with this destructive event through: 1) deployment of a broadband seismic array to record aftershocks; 2) observation of existing eGPS sites; 3) the installation of five new cGPS stations in regions with low site density, but high potential for post-seismic signals. The Nazca plate subducts beneath the South American plate and/or the North Andes block at
~6 cm yr-1, along the Colombia-Ecuador trench, generating M7.5 earthquakes. The 1906 Mw 8.8 earthquake ruptured a large portion of the plate boundary from central Ecuador to central
Colombia. The April 16th, 2016 Mw7.8 earthquake falls within the rupture area of the 1906
event and appears to overlap with the 1942 event. The Pedernales earthquake, offers the opportunity to test the hypothesis that the asperities for large to great earthquakes are persistent over
multiple cycles, and to investigate the role of asperities in arresting slip along strike
and the relationship between locked and creeping parts of the interface. The combined GPS
and seismic data will provide: 1) high precision aftershock locations and focal mechanisms
and their relation to the interplate rupture zone and adjacent segments; 2) detailed structure
of the Pedernales rupture region; 3) characterization of the postseismic deformation field,
including afterslip and viscoelastic relaxation to quantify coseismic and postseismic stress
transfer; 4) identification of low frequency and/or slow slip aftershocks and/or non-volcanic
tremor, and the role of slow slip events in the earthquake cycle; 5) identification of time
varying changes that might reflect rupture zone healing or other time-varying material properties
in the rupture zone; 6) information to characterize site amplification effects and consequent
variable hazard.