Collaborative Research: Acquisition of Continuous GPS and Borehole Geophysical Networks for Investigation of Seismogenic Processes at the Costa Rica Subduction Zone

0502488Schwartz这笔赠款将支持在尼科亚半岛购买和安装由连续运行的GPS站（CGPS）和3个钻孔宽带地震仪和倾斜仪组成的9个站网络，以调查哥斯达黎加俯冲带的慢滑动事件和阵发性地震。新仪器将增强日本和哥斯达黎加同事部署的 3 个现有 CGPS 站，以及德国同事安装的 6 个井下地震观测站。 这些国际合作将极大地增强该网络解决这一危险地区地震过程基本问题的能力。 慢滑移事件或“无声地震”是最近观察到的一种应变释放模式，其中滑移发生在中间时间范围内，通常是几天到几个月。这种类型的运动已在一些存在连续 GPS 或钻孔倾斜计网络的俯冲带断层处被检测到。人们对其中的过程知之甚少，但慢滑动事件与低频地震颤动有关，可能是由流体通过浅俯冲系统的迁移引起的。 板间断层上流体压力的增加可能会削弱它，使其更接近崩溃。因此，慢滑动事件可能表明大地震发生之前的断裂前断裂。 尼科亚半岛钻孔地震和 CGPS 网络将具有足够的密度和灵敏度来检测和研究慢滑动事件和地震颤动，并调查其产生的过程。***

0502488SchwartzThis grant will support acquisition and installation of a 9 station network of continuously operating GPS stations (CGPS) and 3 boreholes broadband seismometers and tiltmeters on the Nicoya Peninsula to investigate slow slip events and episodic seismic tremor at the Costa Rican subduction zone. The new instrumentation will augment 3 existing CGPS stations deployed by Japanese and Costa Rican colleagues, and 6 borehole seismic observatories, being installed by German colleagues. These international collaborations will greatly enhance the ability of the network to address fundamental questions about earthquake processes in this hazardous region. Slow slip events or "silent earthquakes" are a recently observed mode of strain release where slip occurs over an intermediate time scale, usually days to months. This type of motion has been detected at a few subduction zone faults where continuous GPS or borehole tiltmeter networks exist. The processes responsible are poorly understood but slow slip events have been associated with low frequency seismic tremor, possibly caused by the migration of fluids through the shallow subduction system. Increased fluid pressure on the interplate fault could act to weaken it bringing it closer to failure. As a result, slow slip events may indicate pre-rupture fault breakdown prior to the occurrence of a large earthquake. The Nicoya Peninsula borehole seismic and CGPS networks will have sufficient density and sensitivity to detect and study slow slip events and seismic tremor and investigate the processes responsible for their generation.***