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

RAPID：协作：2016 年 4 月 16 日厄瓜多尔 7.8 级佩德纳莱斯地震：凹凸体在破裂传播、余震序列和震后变形中的作用

• 批准号: 1642499
• 负责人: Anne Meltzer
• 金额: $ 8.71万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-15 至 2018-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1642499&HistoricalAwards=false
• 关键词: RAPID; Collaborative; April; 16; 2016

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.

2016 年 4 月 16 日，厄瓜多尔俯冲带发生了 7.8 级地震。这场地震对该国造成了毁灭性打击，造成 660 人死亡、12,000 人受伤，财产损失达 30 亿美元。由于厄瓜多尔是一个经济困难的发展中国家，这种个人和经济损失被放大。来自国际网络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。加拉帕戈斯热点痕迹形成的山脊位于破裂末端的南面，可能限制了地震的范围。这是推动该提案的主要假设之一，也将有助于确定 2016 年地震与 1942 年附近发生的 7.8 级地震之间的关系。20 台宽带地震仪和 5 台连续 GPS 仪器将在 4 月份左右部署在该地区。 16号地震，除了测量现有的GPS纪念碑。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。加拉帕戈斯热点轨道以南地区近期并未发生破裂，但大地测量数据表明该区域已被锁定。由于它更靠近人口稠密的中心瓜亚基尔，因此该锁定段造成了更大的地震危险。2016 年 4 月 16 日，厄瓜多尔佩德纳莱斯附近的哥伦比亚-厄瓜多尔海沟发生了 Mw7.8 级地震。这次地震代表了自 1942 年和 1958 年上次破裂以来沿纳斯卡-南美板块边缘积累的应变的释放。初步数据表明，Mw7.8 地震与 1942 年 Mw7.8 地震使板块界面的同一部分破裂。佩德纳莱斯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个阶段（震间、同震和震后）板块界面上滑移的历史，并研究凹凸体在集中应力、分割破裂方面的作用，促进和/或抑制破裂传播，以及慢滑移事件在地震周期中的作用。与国立理工大学（地理研究所，IG）和军事地理研究所（IGM）的合作将通过以下方式调查与这一破坏性事件相关的震中和震后变形：1）部署宽带地震阵列来记录余震； 2) 观察现有的 eGPS 站点； 3) 在站点密度低但震后信号潜力大的地区安装五个新的 cGPS 站。纳斯卡板块沿哥伦比亚-厄瓜多尔海沟以约 6 cm yr-1 的速度俯冲到南美板块和/或北安第斯地块下方，产生 M7.5 地震。 1906 年发生的 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 Mw7.8 地震位于 1906 年事件的破裂区域内，并且似乎与 1942 年事件重叠。佩德纳莱斯地震提供了检验大地震的粗糙体在多个周期中持续存在的假设的机会，并研究粗糙体在阻止沿走向滑动的作用以及锁定和蠕动之间的关系界面的部分。结合的 GPS 和地震数据将提供：1）高精度余震位置和震源机制及其与板间破裂带和邻近部分的关系； 2）Pedernales破裂区域的详细结构； 3) 震后变形场的表征，包括后滑移和粘弹性松弛，以量化同震和震后应力传递； 4）识别低频和/或慢滑余震和/或非火山地震，以及慢滑事件在地震周期中的作用； 5) 识别随时间变化的变化，这些变化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； 6) 表征站点放大效应和随之而来的变量危害的信息。