Geodetic Observations in the Northern Costa Rica Subduction Zone

2004年（苏门答腊）和2011年（日本）的大地震和海啸敲响了警钟，表明我们对这些灾难性事件的预测能力仍然薄弱。测量活动断层附近地表的缓慢运动有助于预测未来地震的位置和大小。该项目通过在哥斯达黎加运行高精度GPS接收器网络来测试这一概念。这个地区是一个活跃的俯冲带，经常发生大地震。GPS装置将以每天几毫米的精度测量3年期间的地面运动。这将继续这里的大地测量观测的悠久历史，现在跨越了地震周期的后期和早期阶段。该项目的数据将提高对地震过程的理解，并可能提高我们预测这些潜在致命事件的能力。由国家科学基金会资助的测量学联合会联阿援助团将为该网络提供关键的维修支助。这项研究的更广泛影响包括对地震灾害的影响，还通过支持一名博士研究生帮助培养下一代科学家。俯冲界面中地震群的存在表明，并非所有积累的应变都必然在一次地震中释放出来，它们可以储存在一个地震周期中，以便在随后的比平均地震更大的地震中释放出来。随着慢滑事件（sse：在震间相中缓慢释放能量的类似地震的现象）的发现，现在很清楚，确定一个完整的应变积累平衡，并提高对板界面摩擦条件的理解，也需要研究和理解这些震间应变释放机制。2012年哥斯达黎加地震的数据表明，尽管可能存在其他破坏机制，但地震前的SSE对莫尔库仑破坏应力的影响很小。sse也是摩擦条件的重要指标。浅层sse是一个重要的子集，虽然通常很难观察到，但由于靠近海沟，在哥斯达黎加北部可以清楚地看到。它们可能对了解这个难以观测地区的海啸潜力至关重要。更一般地说，SSEs可以勾勒出随后地震破裂的区域，这种模式现在已经在哥斯达黎加、厄瓜多尔和日本部分地区的活动边缘被记录下来。该项目部署了大地测量基础设施，以更好地观察和了解尼科亚半岛的这些慢滑事件。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The great earthquakes and tsunamis of 2004 (Sumatra) and 2011 (Japan) were wake-up calls that our forecasting skill for these catastrophic events remains weak. Measurement of the slow motions of the Earth's surface near active faults could help to forecast the location and the size of future earthquakes. This project tests the concept by operating a network of a high precision GPS receivers in Costa Rica. This area is an active subduction zone that experiences frequent large earthquakes. The GPS units will measure ground motion for a 3-year period with a precision of a few millimeters per day. This will continue a long history of geodetic observations here that now span both the late and early stages of the earthquake cycle. The data from this project will improve understanding of the earthquake process, and could lead to improvements in our ability to forecast these potentially deadly events. UNAVCO, the NSF-funded consortium for geodesy, will provide critical maintenance support for the network. The broader impacts of the study include impacts on earthquake hazards and also help to train the next generation of scientists through support for a PhD graduate student. The existence of earthquake clusters in subduction interfaces suggests that not all accumulated strain is necessarily released in an earthquake, and can be stored over a seismic cycle for release in a subsequent, larger than average event. With the discovery of slow slip events (SSEs: earthquake-like phenomenon within the interseismic phase that release energy slowly) it is now clear that determination of a full strain accumulation budget, and improved understanding of frictional conditions on the plate interface, also require study and understanding of these interseismic strain release mechanisms. Data from the 2012 Costa Rica earthquake suggests that a pre-event SSE changed Mohr Coulomb failure stress by a trivial amount, although other failure mechanisms are possible. SSEs are also important indicators of frictional conditions. Shallow SSEs are an important subset, and while generally difficult to observe, can be clearly seen in northern Costa Rica due to proximity to the trench. They may be critical for understanding tsunami potential in this difficult-to-observe region. More generally, SSEs may outline the region of subsequent seismic rupture, this pattern has now been documented in the active margins off Costa Rica, Ecuador and parts of Japan. This project deploys geodetic infrastructure to better observe and understand these slow slip events in the Nicoya Peninsula.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.