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，厄瓜多尔俯冲带沿线发生7.8级地震。这场地震对这个国家造成了毁灭性的破坏，造成660人死亡，12000人受伤，30亿美元的财产损失。这种个人和经济损失被放大，因为厄瓜多尔是一个发展中国家，经济陷入困境。来自国际地震台网的初步地震数据表明，4月16日的地震沿着南美板块和纳斯卡板块之间的界面从北向南破裂。加拉帕戈斯热点的痕迹形成的山脊正好位于断裂末端的南面，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年地震和1942年发生在附近的7.8兆瓦地震之间的关系。除了调查现有的GPS纪念碑外，4月16日地震前后，该地区还将部署20台宽带地震仪和5台连续GPS仪器。这些地震和GPS部署旨在补充现有的厄瓜多尔国家台网，以更详细地绘制余震序列图，并评估俯冲带各部分之间的应力传递。加拉帕戈斯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。由于距离人口中心瓜亚基尔更近，这段被锁住的地段构成了更大的地震危险。2016年4月16日，厄瓜多尔Pedernales附近的哥伦比亚-厄瓜多尔海沟发生7.8级地震。这次地震代表着纳斯卡-南美板块边缘自1942年和1958年上次破裂以来累积应变的释放。初步数据表明，Mw7.8级地震与1942年Mw7.8级地震破裂的板块界面部分相同。Pedernales地震提供了一个机会，可以使用最先进的技术来测量地震周期各阶段(地震间、同震和震后)板块界面上的滑动历史，并研究凹凸体在集中应力、分割破裂、促进和/或抑制破裂传播方面的作用，以及慢滑事件在地震周期中的作用。与Escuela Politecnica National(Instituto Geofisico，IG)和Instituto Geografio Military(IGM)的合作将通过以下方式调查与这一破坏性事件有关的同震和震后变形：1)部署宽带地震阵列记录余震；2)观察现有的eGPS站点；3)在场地密度低但震后信号潜力大的地区安装5个新的CGPS站点。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-厄瓜多尔海沟在&amp；#8232；~6 cm yr-1处发生7.5级地震。1906年发生的8.8兆赫地震使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年地震的破裂区域内，似乎与1942年的地震重叠。Pedernales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凹凸体在多个旋回中持续存在，并研究凹凸体在阻止沿走向滑动的过程中的作用，以及界面锁定部分和蠕动部分之间的关系。GPS和地震组合数据将提供：1)高精度余震位置和震源机制及其与板间破裂带和相邻分段的关系；2)Pedernales断裂区的详细结构；3)震后形变场的特征，包括余滑和粘弹性松弛，以量化同震应力和震后应力；4)识别低频和/或慢滑余震和/或非火山和非火山震颤，以及慢滑事件在地震周期中的作用；5)确定可能反映破裂区愈合或破裂区中其他随时间变化的材料特性的时间变化；6)表征现场放大效应和由此产生的可变危险的信息。

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.